Spring IOC设计原理解析:本文乃学习整理参考而来

一、 什么是Ioc/DI？

二、 Spring IOC体系结构

(1) BeanFactory

(2) BeanDefinition

三、 IoC容器的初始化

1、 XmlBeanFactory(屌丝IOC)的整个流程

2、 FileSystemXmlApplicationContext 的IOC容器流程

1、高富帅IOC解剖

2、 设置资源加载器和资源定位

3、AbstractApplicationContext的refresh函数载入Bean定义过程：

4、AbstractApplicationContext子类的refreshBeanFactory()方法：

5、AbstractRefreshableApplicationContext子类的loadBeanDefinitions方法：

6、AbstractBeanDefinitionReader读取Bean定义资源：

7、资源加载器获取要读入的资源：

8、XmlBeanDefinitionReader加载Bean定义资源：

9、DocumentLoader将Bean定义资源转换为Document对象：

10、XmlBeanDefinitionReader解析载入的Bean定义资源文件：

11、DefaultBeanDefinitionDocumentReader对Bean定义的Document对象解析：

12、BeanDefinitionParserDelegate解析Bean定义资源文件中的<Bean>元素：

13、BeanDefinitionParserDelegate解析<property>元素：

14、解析<property>元素的子元素：

15、解析<list>子元素：

16、解析过后的BeanDefinition在IoC容器中的注册：

17、DefaultListableBeanFactory向IoC容器注册解析后的BeanDefinition：

总结：

四、IOC容器的依赖注入

1、依赖注入发生的时间

2、AbstractBeanFactory通过getBean向IoC容器获取被管理的Bean：

3、AbstractAutowireCapableBeanFactory创建Bean实例对象：

4、createBeanInstance方法创建Bean的java实例对象：

5、SimpleInstantiationStrategy类使用默认的无参构造方法创建Bean实例化对象：

6、populateBean方法对Bean属性的依赖注入：

7、BeanDefinitionValueResolver解析属性值：

8、BeanWrapperImpl对Bean属性的依赖注入：

五、IoC容器的高级特性

1、介绍

2、Spring IoC容器的lazy-init属性实现预实例化：

(1) .refresh()

(2).finishBeanFactoryInitialization处理预实例化Bean：

(3) .DefaultListableBeanFactory对配置lazy-init属性单态Bean的预实例化：

3、FactoryBean的实现：

(1).FactoryBean的源码如下：

(2). AbstractBeanFactory的getBean方法调用FactoryBean：

(3)、AbstractBeanFactory生产Bean实例对象：

(4).工厂Bean的实现类getObject方法创建Bean实例对象：

4.BeanPostProcessor后置处理器的实现：

(1).BeanPostProcessor的源码如下：

(2).AbstractAutowireCapableBeanFactory类对容器生成的Bean添加后置处理器：

(3).initializeBean方法为容器产生的Bean实例对象添加BeanPostProcessor后置处理器：

(4).AdvisorAdapterRegistrationManager在Bean对象初始化后注册通知适配器：

5.Spring IoC容器autowiring实现原理：

(1). AbstractAutoWireCapableBeanFactory对Bean实例进行属性依赖注入：

(2).Spring IoC容器根据Bean名称或者类型进行autowiring自动依赖注入：

(3).DefaultSingletonBeanRegistry的registerDependentBean方法对属性注入：

一、什么是Ioc/DI？

二、 Spring IOC体系结构？

1 public interface BeanFactory {
23 //对FactoryBean的转义定义，因为如果使用bean的名字检索FactoryBean得到的对象是工厂生成的对象， 4 //如果需要得到工厂本身，需要转义 5 String FACTORY_BEAN_PREFIX = "&";
67 //根据bean的名字，获取在IOC容器中得到bean实例 8 Object getBean(String name) throws BeansException;
910 //根据bean的名字和Class类型来得到bean实例，增加了类型安全验证机制。 11 Object getBean(String name, Class requiredType) throws BeansException;
1213 //提供对bean的检索，看看是否在IOC容器有这个名字的bean 14 boolean containsBean(String name);
1516 //根据bean名字得到bean实例，并同时判断这个bean是不是单例 17 boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
1819 //得到bean实例的Class类型 20 Class getType(String name) throws NoSuchBeanDefinitionException;
2122 //得到bean的别名，如果根据别名检索，那么其原名也会被检索出来 23 String[] getAliases(String name);
24
}

三、IoC容器的初始化？

public class XmlBeanFactory extends DefaultListableBeanFactory{

private final XmlBeanDefinitionReader reader;

public XmlBeanFactory(Resource resource)throws BeansException{
this(resource, null);
}

public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory)
throws BeansException{
super(parentBeanFactory);
this.reader = new XmlBeanDefinitionReader(this);
this.reader.loadBeanDefinitions(resource);
}
}

//根据Xml配置文件创建Resource资源对象，该对象中包含了BeanDefinition的信息
ClassPathResource resource =new ClassPathResource("application-context.xml");
//创建DefaultListableBeanFactory
DefaultListableBeanFactory factory =new DefaultListableBeanFactory();
//创建XmlBeanDefinitionReader读取器，用于载入BeanDefinition。之所以需要BeanFactory作为参数，是因为会将读取的信息回调配置给factory
XmlBeanDefinitionReader reader =new XmlBeanDefinitionReader(factory);
//XmlBeanDefinitionReader执行载入BeanDefinition的方法，最后会完成Bean的载入和注册。完成后Bean就成功的放置到IOC容器当中，以后我们就可以从中取得Bean来使用
reader.loadBeanDefinitions(resource);

/**
* Create a new FileSystemXmlApplicationContext, loading the definitions
* from the given XML files and automatically refreshing the context.
* @param configLocations array of file paths
* @throws BeansException if context creation failed
*/public FileSystemXmlApplicationContext(String... configLocations) throws BeansException {
this(configLocations, true, null);
}

public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}

public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext, DisposableBean {
//静态初始化块，在整个容器创建过程中只执行一次 static {
//为了避免应用程序在Weblogic8.1关闭时出现类加载异常加载问题，加载IoC容
//器关闭事件(ContextClosedEvent)类
ContextClosedEvent.class.getName();
}
//FileSystemXmlApplicationContext调用父类构造方法调用的就是该方法 public AbstractApplicationContext(ApplicationContext parent) {
this.parent = parent;
this.resourcePatternResolver = getResourcePatternResolver();
}
//获取一个Spring Source的加载器用于读入Spring Bean定义资源文件 protected ResourcePatternResolver getResourcePatternResolver() {
// AbstractApplicationContext继承DefaultResourceLoader，也是一个S
//Spring资源加载器，其getResource(String location)方法用于载入资源 return new PathMatchingResourcePatternResolver(this);
}
……
}

public PathMatchingResourcePatternResolver(ResourceLoader resourceLoader) {
Assert.notNull(resourceLoader, "ResourceLoader must not be null");
//设置Spring的资源加载器 this.resourceLoader = resourceLoader;
}

//处理单个资源文件路径为一个字符串的情况 public void setConfigLocation(String location) {
//String CONFIG_LOCATION_DELIMITERS = ",; /t/n";
//即多个资源文件路径之间用” ,; /t/n”分隔，解析成数组形式 setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS));
}
//解析Bean定义资源文件的路径，处理多个资源文件字符串数组 public void setConfigLocations(String[] locations) {
if (locations != null) {
Assert.noNullElements(locations, "Config locations must not be null");
this.configLocations = new String[locations.length];
for (int i = 0; i < locations.length; i++) {
// resolvePath为同一个类中将字符串解析为路径的方法 this.configLocations[i] = resolvePath(locations[i]).trim();
}
}
else {
this.configLocations = null;
}
}

1 public void refresh() throws BeansException, IllegalStateException {
2 synchronized (this.startupShutdownMonitor) {
3 //调用容器准备刷新的方法，获取容器的当时时间，同时给容器设置同步标识 4 prepareRefresh();
5 //告诉子类启动refreshBeanFactory()方法，Bean定义资源文件的载入从 6 //子类的refreshBeanFactory()方法启动 7 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
8 //为BeanFactory配置容器特性，例如类加载器、事件处理器等 9 prepareBeanFactory(beanFactory);
10 try {
11 //为容器的某些子类指定特殊的BeanPost事件处理器 12 postProcessBeanFactory(beanFactory);
13 //调用所有注册的BeanFactoryPostProcessor的Bean 14 invokeBeanFactoryPostProcessors(beanFactory);
15 //为BeanFactory注册BeanPost事件处理器. 16 //BeanPostProcessor是Bean后置处理器，用于监听容器触发的事件 17 registerBeanPostProcessors(beanFactory);
18 //初始化信息源，和国际化相关. 19 initMessageSource();
20 //初始化容器事件传播器. 21 initApplicationEventMulticaster();
22 //调用子类的某些特殊Bean初始化方法 23 onRefresh();
24 //为事件传播器注册事件监听器. 25 registerListeners();
26 //初始化所有剩余的单态Bean. 27 finishBeanFactoryInitialization(beanFactory);
28 //初始化容器的生命周期事件处理器，并发布容器的生命周期事件 29 finishRefresh();
30 }
31 catch (BeansException ex) {
32 //销毁以创建的单态Bean 33 destroyBeans();
34 //取消refresh操作，重置容器的同步标识. 35 cancelRefresh(ex);
36 throw ex;
37 }
38 }
39 }

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
//这里使用了委派设计模式，父类定义了抽象的refreshBeanFactory()方法，具体实现调用子类容器的refreshBeanFactory()方法 refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}

1 protected final void refreshBeanFactory() throws BeansException {
2 if (hasBeanFactory()) {//如果已经有容器，销毁容器中的bean，关闭容器 3 destroyBeans();
4 closeBeanFactory();
5 }
6 try {
7 //创建IoC容器 8 DefaultListableBeanFactory beanFactory = createBeanFactory();
9 beanFactory.setSerializationId(getId());
10 //对IoC容器进行定制化，如设置启动参数，开启注解的自动装配等 11 customizeBeanFactory(beanFactory);
12 //调用载入Bean定义的方法，主要这里又使用了一个委派模式，在当前类中只定义了抽象的loadBeanDefinitions方法，具体的实现调用子类容器 13 loadBeanDefinitions(beanFactory);
14 synchronized (this.beanFactoryMonitor) {
15 this.beanFactory = beanFactory;
16 }
17 }
18 catch (IOException ex) {
19 throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
20 }
21 }

1 public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext {
2 ……
3 //实现父类抽象的载入Bean定义方法 4 @Override
5 protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
6 //创建XmlBeanDefinitionReader，即创建Bean读取器，并通过回调设置到容器中去，容 器使用该读取器读取Bean定义资源 7 XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
8 //为Bean读取器设置Spring资源加载器，AbstractXmlApplicationContext的 9 //祖先父类AbstractApplicationContext继承DefaultResourceLoader，因此，容器本身也是一个资源加载器 10 beanDefinitionReader.setResourceLoader(this);
11 //为Bean读取器设置SAX xml解析器 12 beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
13 //当Bean读取器读取Bean定义的Xml资源文件时，启用Xml的校验机制 14 initBeanDefinitionReader(beanDefinitionReader);
15 //Bean读取器真正实现加载的方法 16 loadBeanDefinitions(beanDefinitionReader);
17 }
18 //Xml Bean读取器加载Bean定义资源 19 protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
20 //获取Bean定义资源的定位 21 Resource[] configResources = getConfigResources();
22 if (configResources != null) {
23 //Xml Bean读取器调用其父类AbstractBeanDefinitionReader读取定位 24 //的Bean定义资源 25 reader.loadBeanDefinitions(configResources);
26 }
27 //如果子类中获取的Bean定义资源定位为空，则获取FileSystemXmlApplicationContext构造方法中setConfigLocations方法设置的资源 28 String[] configLocations = getConfigLocations();
29 if (configLocations != null) {
30 //Xml Bean读取器调用其父类AbstractBeanDefinitionReader读取定位 31 //的Bean定义资源 32 reader.loadBeanDefinitions(configLocations);
33 }
34 }
35 //这里又使用了一个委托模式，调用子类的获取Bean定义资源定位的方法 36 //该方法在ClassPathXmlApplicationContext中进行实现，对于我们 37 //举例分析源码的FileSystemXmlApplicationContext没有使用该方法
38 protected Resource[] getConfigResources() {
39 return null;
40 } ……
41}

1 //重载方法，调用下面的loadBeanDefinitions(String, Set<Resource>);方法 2 public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
3 return loadBeanDefinitions(location, null);
4 }
5 public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {
6 //获取在IoC容器初始化过程中设置的资源加载器 7 ResourceLoader resourceLoader = getResourceLoader();
8 if (resourceLoader == null) {
9 throw new BeanDefinitionStoreException(
10 "Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
11 }
12 if (resourceLoader instanceof ResourcePatternResolver) {
13 try {
14 //将指定位置的Bean定义资源文件解析为Spring IoC容器封装的资源 15 //加载多个指定位置的Bean定义资源文件 16 Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
17 //委派调用其子类XmlBeanDefinitionReader的方法，实现加载功能 18 int loadCount = loadBeanDefinitions(resources);
19 if (actualResources != null) {
20 for (Resource resource : resources) {
21 actualResources.add(resource);
22 }
23 }
24 if (logger.isDebugEnabled()) {
25 logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
26 }
27 return loadCount;
28 }
29 catch (IOException ex) {
30 throw new BeanDefinitionStoreException(
31 "Could not resolve bean definition resource pattern [" + location + "]", ex);
32 }
33 }
34 else {
35 //将指定位置的Bean定义资源文件解析为Spring IoC容器封装的资源 36 //加载单个指定位置的Bean定义资源文件 37 Resource resource = resourceLoader.getResource(location);
38 //委派调用其子类XmlBeanDefinitionReader的方法，实现加载功能 39 int loadCount = loadBeanDefinitions(resource);
40 if (actualResources != null) {
41 actualResources.add(resource);
42 }
43 if (logger.isDebugEnabled()) {
44 logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
45 }
46 return loadCount;
47 }
48 }
49 //重载方法，调用loadBeanDefinitions(String); 50 public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
51 Assert.notNull(locations, "Location array must not be null");
52 int counter = 0;
53 for (String location : locations) {
54 counter += loadBeanDefinitions(location);
55 }
56 return counter;
}

1 //获取Resource的具体实现方法
2 public Resource getResource(String location) {
3 Assert.notNull(location, "Location must not be null");
4 //如果是类路径的方式，那需要使用ClassPathResource 来得到bean 文件的资源对象 5 if (location.startsWith(CLASSPATH_URL_PREFIX)) {
6 return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()), getClassLoader());
7 }
8 try {
9 // 如果是URL 方式，使用UrlResource 作为bean 文件的资源对象 10 URL url = new URL(location);
11 return new UrlResource(url);
12 }
13 catch (MalformedURLException ex) {
14 }
15 //如果既不是classpath标识，又不是URL标识的Resource定位，则调用 16 //容器本身的getResourceByPath方法获取Resource 17 return getResourceByPath(location);
1819 }

protected Resource getResourceByPath(String path) {
if (path != null && path.startsWith("/")) {
path = path.substring(1);
}
//这里使用文件系统资源对象来定义bean 文件return new FileSystemResource(path);
}

1 //XmlBeanDefinitionReader加载资源的入口方法
2 public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
3 //将读入的XML资源进行特殊编码处理 4 return loadBeanDefinitions(new EncodedResource(resource));
5 }
//这里是载入XML形式Bean定义资源文件方法
6 public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
7 .......
8 try {
9 //将资源文件转为InputStream的IO流 10 InputStream inputStream = encodedResource.getResource().getInputStream();
11 try {
12 //从InputStream中得到XML的解析源 13 InputSource inputSource = new InputSource(inputStream);
14 if (encodedResource.getEncoding() != null) {
15 inputSource.setEncoding(encodedResource.getEncoding());
16 }
17 //这里是具体的读取过程 18 return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
19 }
20 finally {
21 //关闭从Resource中得到的IO流 22 inputStream.close();
23 }
24 }
25 .........
26}
27 //从特定XML文件中实际载入Bean定义资源的方法
28 protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
29 throws BeanDefinitionStoreException {
30 try {
31 int validationMode = getValidationModeForResource(resource);
32 //将XML文件转换为DOM对象，解析过程由documentLoader实现 33 Document doc = this.documentLoader.loadDocument(
34 inputSource, this.entityResolver, this.errorHandler, validationMode, this.namespaceAware);
35 //这里是启动对Bean定义解析的详细过程，该解析过程会用到Spring的Bean配置规则36 return registerBeanDefinitions(doc, resource);
37 }
38 .......
}

1 //使用标准的JAXP将载入的Bean定义资源转换成document对象
2 public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
3 ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
4 //创建文件解析器工厂 5 DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
6 if (logger.isDebugEnabled()) {
7 logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
8 }
9 //创建文档解析器 10 DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
11 //解析Spring的Bean定义资源 12 return builder.parse(inputSource);
13 }
14 protected DocumentBuilderFactory createDocumentBuilderFactory(int validationMode, boolean namespaceAware)
15 throws ParserConfigurationException {
16 //创建文档解析工厂 17 DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
18 factory.setNamespaceAware(namespaceAware);
19 //设置解析XML的校验 20 if (validationMode != XmlValidationModeDetector.VALIDATION_NONE) {
21 factory.setValidating(true);
22 if (validationMode == XmlValidationModeDetector.VALIDATION_XSD) {
23 factory.setNamespaceAware(true);
24 try {
25 factory.setAttribute(SCHEMA_LANGUAGE_ATTRIBUTE, XSD_SCHEMA_LANGUAGE);
26 }
27 catch (IllegalArgumentException ex) {
28 ParserConfigurationException pcex = new ParserConfigurationException(
29 "Unable to validate using XSD: Your JAXP provider [" + factory +
30 "] does not support XML Schema. Are you running on Java 1.4 with Apache Crimson? " +
31 "Upgrade to Apache Xerces (or Java 1.5) for full XSD support.");
32 pcex.initCause(ex);
33 throw pcex;
34 }
35 }
36 }
37 return factory;
38 }

1 //按照Spring的Bean语义要求将Bean定义资源解析并转换为容器内部数据结构
2 public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
3 //得到BeanDefinitionDocumentReader来对xml格式的BeanDefinition解析 4 BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
5 //获得容器中注册的Bean数量 6 int countBefore = getRegistry().getBeanDefinitionCount();
7 //解析过程入口，这里使用了委派模式，BeanDefinitionDocumentReader只是个接口，//具体的解析实现过程有实现类DefaultBeanDefinitionDocumentReader完成 8 documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
9 //统计解析的Bean数量 10 return getRegistry().getBeanDefinitionCount() - countBefore;
11 }
12 //创建BeanDefinitionDocumentReader对象，解析Document对象
13 protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() {
14 return BeanDefinitionDocumentReader.class.cast(BeanUtils.instantiateClass(this.documentReaderClass));
}

1 //根据Spring DTD对Bean的定义规则解析Bean定义Document对象
2 public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
3 //获得XML描述符 4 this.readerContext = readerContext;
5 logger.debug("Loading bean definitions");
6 //获得Document的根元素 7 Element root = doc.getDocumentElement();
8 //具体的解析过程由BeanDefinitionParserDelegate实现， 9 //BeanDefinitionParserDelegate中定义了Spring Bean定义XML文件的各种元素 10 BeanDefinitionParserDelegate delegate = createHelper(readerContext, root);
11 //在解析Bean定义之前，进行自定义的解析，增强解析过程的可扩展性 12 preProcessXml(root);
13 //从Document的根元素开始进行Bean定义的Document对象 14 parseBeanDefinitions(root, delegate);
15 //在解析Bean定义之后，进行自定义的解析，增加解析过程的可扩展性 16 postProcessXml(root);
17 }
18 //创建BeanDefinitionParserDelegate，用于完成真正的解析过程 19 protected BeanDefinitionParserDelegate createHelper(XmlReaderContext readerContext, Element root) {
20 BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);
21 //BeanDefinitionParserDelegate初始化Document根元素 22 delegate.initDefaults(root);
23 return delegate;
24 }
25 //使用Spring的Bean规则从Document的根元素开始进行Bean定义的Document对象 26 protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
27 //Bean定义的Document对象使用了Spring默认的XML命名空间 28 if (delegate.isDefaultNamespace(root)) {
29 //获取Bean定义的Document对象根元素的所有子节点 30 NodeList nl = root.getChildNodes();
31 for (int i = 0; i < nl.getLength(); i++) {
32 Node node = nl.item(i);
33 //获得Document节点是XML元素节点 34 if (node instanceof Element) {
35 Element ele = (Element) node;
36 //Bean定义的Document的元素节点使用的是Spring默认的XML命名空间 37 if (delegate.isDefaultNamespace(ele)) {
38 //使用Spring的Bean规则解析元素节点 39 parseDefaultElement(ele, delegate);
40 }
41 else {
42 //没有使用Spring默认的XML命名空间，则使用用户自定义的解//析规则解析元素节点 43 delegate.parseCustomElement(ele);
44 }
45 }
46 }
47 }
48 else {
49 //Document的根节点没有使用Spring默认的命名空间，则使用用户自定义的 50 //解析规则解析Document根节点 51 delegate.parseCustomElement(root);
52 }
53 }
54 //使用Spring的Bean规则解析Document元素节点 55 private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
56 //如果元素节点是<Import>导入元素，进行导入解析
57 if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
58 importBeanDefinitionResource(ele);
59 }
60 //如果元素节点是<Alias>别名元素，进行别名解析 61 else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
62 processAliasRegistration(ele);
63 }
64 //元素节点既不是导入元素，也不是别名元素，即普通的<Bean>元素， 65 //按照Spring的Bean规则解析元素 66 else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
67 processBeanDefinition(ele, delegate);
68 }
69 }
70 //解析<Import>导入元素，从给定的导入路径加载Bean定义资源到Spring IoC容器中 71 protected void importBeanDefinitionResource(Element ele) {
72 //获取给定的导入元素的location属性
73 String location = ele.getAttribute(RESOURCE_ATTRIBUTE);
74 //如果导入元素的location属性值为空，则没有导入任何资源，直接返回
75 if (!StringUtils.hasText(location)) {
76 getReaderContext().error("Resource location must not be empty", ele);
77 return;
78 }
79 //使用系统变量值解析location属性值 80 location = SystemPropertyUtils.resolvePlaceholders(location);
81 Set<Resource> actualResources = new LinkedHashSet<Resource>(4);
82 //标识给定的导入元素的location是否是绝对路径 83 boolean absoluteLocation = false;
84 try {
85 absoluteLocation = ResourcePatternUtils.isUrl(location) || ResourceUtils.toURI(location).isAbsolute();
86 }
87 catch (URISyntaxException ex) {
88 //给定的导入元素的location不是绝对路径 89 }
90 //给定的导入元素的location是绝对路径 91 if (absoluteLocation) {
92 try {
93 //使用资源读入器加载给定路径的Bean定义资源 94 int importCount = getReaderContext().getReader().loadBeanDefinitions(location, actualResources);
95 if (logger.isDebugEnabled()) {
96 logger.debug("Imported " + importCount + " bean definitions from URL location [" + location + "]");
97 }
98 }
99 catch (BeanDefinitionStoreException ex) {
100 getReaderContext().error(
101 "Failed to import bean definitions from URL location [" + location + "]", ele, ex);
102 }
103 }
104 else {
105 //给定的导入元素的location是相对路径 106 try {
107 int importCount;
108 //将给定导入元素的location封装为相对路径资源 109 Resource relativeResource = getReaderContext().getResource().createRelative(location);
110 //封装的相对路径资源存在 111 if (relativeResource.exists()) {
112 //使用资源读入器加载Bean定义资源 113 importCount = getReaderContext().getReader().loadBeanDefinitions(relativeResource);
114 actualResources.add(relativeResource);
115 }
116 //封装的相对路径资源不存在 117 else {
118 //获取Spring IoC容器资源读入器的基本路径 119 String baseLocation = getReaderContext().getResource().getURL().toString();
120 //根据Spring IoC容器资源读入器的基本路径加载给定导入 121 //路径的资源 122 importCount = getReaderContext().getReader().loadBeanDefinitions(
123 StringUtils.applyRelativePath(baseLocation, location), actualResources);
124 }
125 if (logger.isDebugEnabled()) {
126 logger.debug("Imported " + importCount + " bean definitions from relative location [" + location + "]");
127 }
128 }
129 catch (IOException ex) {
130 getReaderContext().error("Failed to resolve current resource location", ele, ex);
131 }
132 catch (BeanDefinitionStoreException ex) {
133 getReaderContext().error("Failed to import bean definitions from relative location [" + location + "]",
134 ele, ex);
135 }
136 }
137 Resource[] actResArray = actualResources.toArray(new Resource[actualResources.size()]);
138 //在解析完<Import>元素之后，发送容器导入其他资源处理完成事件 139 getReaderContext().fireImportProcessed(location, actResArray, extractSource(ele));
140 }
141 //解析<Alias>别名元素，为Bean向Spring IoC容器注册别名 142 protected void processAliasRegistration(Element ele) {
143 //获取<Alias>别名元素中name的属性值
144 String name = ele.getAttribute(NAME_ATTRIBUTE);
145 //获取<Alias>别名元素中alias的属性值 146 String alias = ele.getAttribute(ALIAS_ATTRIBUTE);
147 boolean valid = true;
148 //<alias>别名元素的name属性值为空
149 if (!StringUtils.hasText(name)) {
150 getReaderContext().error("Name must not be empty", ele);
151 valid = false;
152 }
153 //<alias>别名元素的alias属性值为空 154 if (!StringUtils.hasText(alias)) {
155 getReaderContext().error("Alias must not be empty", ele);
156 valid = false;
157 }
158 if (valid) {
159 try {
160 //向容器的资源读入器注册别名 161 getReaderContext().getRegistry().registerAlias(name, alias);
162 }
163 catch (Exception ex) {
164 getReaderContext().error("Failed to register alias '" + alias +
165 "' for bean with name '" + name + "'", ele, ex);
166 }
167 //在解析完<Alias>元素之后，发送容器别名处理完成事件 168 getReaderContext().fireAliasRegistered(name, alias, extractSource(ele));
169 }
170 }
171 //解析Bean定义资源Document对象的普通元素 172 protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
173 // BeanDefinitionHolder是对BeanDefinition的封装，即Bean定义的封装类 174 //对Document对象中<Bean>元素的解析由BeanDefinitionParserDelegate实现 BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); 175 if (bdHolder != null) {
176 bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
177 try {
178 //向Spring IoC容器注册解析得到的Bean定义，这是Bean定义向IoC容器注册的入口
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); 179 }
180 catch (BeanDefinitionStoreException ex) {
181 getReaderContext().error("Failed to register bean definition with name '" +
182 bdHolder.getBeanName() + "'", ele, ex);
183 }
184 //在完成向Spring IoC容器注册解析得到的Bean定义之后，发送注册事件 185 getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
186 }
187 }

1 //解析<Bean>元素的入口
2 public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
3 return parseBeanDefinitionElement(ele, null);
4 }
5 //解析Bean定义资源文件中的<Bean>元素，这个方法中主要处理<Bean>元素的id，name 6 //和别名属性 7 public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
8 //获取<Bean>元素中的id属性值 9 String id = ele.getAttribute(ID_ATTRIBUTE);
10 //获取<Bean>元素中的name属性值 11 String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
12 ////获取<Bean>元素中的alias属性值 13 List<String> aliases = new ArrayList<String>();
14 //将<Bean>元素中的所有name属性值存放到别名中
15 if (StringUtils.hasLength(nameAttr)) {
16 String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, BEAN_NAME_DELIMITERS);
17 aliases.addAll(Arrays.asList(nameArr));
18 }
19 String beanName = id;
20 //如果<Bean>元素中没有配置id属性时，将别名中的第一个值赋值给beanName 21 if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
22 beanName = aliases.remove(0);
23 if (logger.isDebugEnabled()) {
24 logger.debug("No XML 'id' specified - using '" + beanName +
25 "' as bean name and " + aliases + " as aliases");
26 }
27 }
28 //检查<Bean>元素所配置的id或者name的唯一性，containingBean标识<Bean> 29 //元素中是否包含子<Bean>元素 30 if (containingBean == null) {
31 //检查<Bean>元素所配置的id、name或者别名是否重复 32 checkNameUniqueness(beanName, aliases, ele);
33 }
34 //详细对<Bean>元素中配置的Bean定义进行解析的地方 35 AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
36 if (beanDefinition != null) {
37 if (!StringUtils.hasText(beanName)) {
38 try {
39 if (containingBean != null) {
40 //如果<Bean>元素中没有配置id、别名或者name，且没有包含子//<Bean>元素，为解析的Bean生成一个唯一beanName并注册 41 beanName = BeanDefinitionReaderUtils.generateBeanName(
42 beanDefinition, this.readerContext.getRegistry(), true);
43 }
44 else {
45 //如果<Bean>元素中没有配置id、别名或者name，且包含了子//<Bean>元素，为解析的Bean使用别名向IoC容器注册 46 beanName = this.readerContext.generateBeanName(beanDefinition);
47 //为解析的Bean使用别名注册时，为了向后兼容 //Spring1.2/2.0，给别名添加类名后缀 48 String beanClassName = beanDefinition.getBeanClassName();
49 if (beanClassName != null &&
50 beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
51 !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
52 aliases.add(beanClassName);
53 }
54 }
55 if (logger.isDebugEnabled()) {
56 logger.debug("Neither XML 'id' nor 'name' specified - " +
57 "using generated bean name [" + beanName + "]");
58 }
59 }
60 catch (Exception ex) {
61 error(ex.getMessage(), ele);
62 return null;
63 }
64 }
65 String[] aliasesArray = StringUtils.toStringArray(aliases);
66 return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
67 }
68 //当解析出错时，返回null 69 return null;
70 }
71 //详细对<Bean>元素中配置的Bean定义其他属性进行解析，由于上面的方法中已经对//Bean的id、name和别名等属性进行了处理，该方法中主要处理除这三个以外的其他属性数据
72 public AbstractBeanDefinition parseBeanDefinitionElement(
73 Element ele, String beanName, BeanDefinition containingBean) {
74 //记录解析的<Bean> 75 this.parseState.push(new BeanEntry(beanName));
76 //这里只读取<Bean>元素中配置的class名字，然后载入到BeanDefinition中去 77 //只是记录配置的class名字，不做实例化，对象的实例化在依赖注入时完成 78 String className = null;
79 if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
80 className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
81 }
82 try {
83 String parent = null;
84 //如果<Bean>元素中配置了parent属性，则获取parent属性的值 85 if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
86 parent = ele.getAttribute(PARENT_ATTRIBUTE);
87 }
88 //根据<Bean>元素配置的class名称和parent属性值创建BeanDefinition 89 //为载入Bean定义信息做准备 90 AbstractBeanDefinition bd = createBeanDefinition(className, parent);
91 //对当前的<Bean>元素中配置的一些属性进行解析和设置，如配置的单态(singleton)属性等 92 parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
93 //为<Bean>元素解析的Bean设置description信息 bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT)); 94 //对<Bean>元素的meta(元信息)属性解析 95 parseMetaElements(ele, bd);
96 //对<Bean>元素的lookup-method属性解析 97 parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
98 //对<Bean>元素的replaced-method属性解析 99 parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
100 //解析<Bean>元素的构造方法设置 101 parseConstructorArgElements(ele, bd);
102 //解析<Bean>元素的<property>设置 103 parsePropertyElements(ele, bd);
104 //解析<Bean>元素的qualifier属性 105 parseQualifierElements(ele, bd);
106 //为当前解析的Bean设置所需的资源和依赖对象 107 bd.setResource(this.readerContext.getResource());
108 bd.setSource(extractSource(ele));
109 return bd;
110 }
111 catch (ClassNotFoundException ex) {
112 error("Bean class [" + className + "] not found", ele, ex);
113 }
114 catch (NoClassDefFoundError err) {
115 error("Class that bean class [" + className + "] depends on not found", ele, err);
116 }
117 catch (Throwable ex) {
118 error("Unexpected failure during bean definition parsing", ele, ex);
119 }
120 finally {
121 this.parseState.pop();
122 }
123 //解析<Bean>元素出错时，返回null 124 return null;
125 }

1 //解析<Bean>元素中的<property>子元素
2 public void parsePropertyElements(Element beanEle, BeanDefinition bd) {
3 //获取<Bean>元素中所有的子元素
4 NodeList nl = beanEle.getChildNodes();
5 for (int i = 0; i < nl.getLength(); i++) {
6 Node node = nl.item(i);
7 //如果子元素是<property>子元素，则调用解析<property>子元素方法解析 8 if (isCandidateElement(node) && nodeNameEquals(node, PROPERTY_ELEMENT)) {
9 parsePropertyElement((Element) node, bd);
10 }
11 }
12 }
13 //解析<property>元素
14 public void parsePropertyElement(Element ele, BeanDefinition bd) {
15 //获取<property>元素的名字 16 String propertyName = ele.getAttribute(NAME_ATTRIBUTE);
17 if (!StringUtils.hasLength(propertyName)) {
18 error("Tag 'property' must have a 'name' attribute", ele);
19 return;
20 }
21 this.parseState.push(new PropertyEntry(propertyName));
22 try {
23 //如果一个Bean中已经有同名的property存在，则不进行解析，直接返回。 24 //即如果在同一个Bean中配置同名的property，则只有第一个起作用 25 if (bd.getPropertyValues().contains(propertyName)) {
26 error("Multiple 'property' definitions for property '" + propertyName + "'", ele);
27 return;
28 }
29 //解析获取property的值 30 Object val = parsePropertyValue(ele, bd, propertyName);
31 //根据property的名字和值创建property实例 32 PropertyValue pv = new PropertyValue(propertyName, val);
33 //解析<property>元素中的属性 34 parseMetaElements(ele, pv);
35 pv.setSource(extractSource(ele));
36 bd.getPropertyValues().addPropertyValue(pv);
37 }
38 finally {
39 this.parseState.pop();
40 }
41 }
42 //解析获取property值
43 public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) {
44 String elementName = (propertyName != null) ?
45 "<property> element for property '" + propertyName + "'" :
46 "<constructor-arg> element";
47 //获取<property>的所有子元素，只能是其中一种类型:ref,value,list等 48 NodeList nl = ele.getChildNodes();
49 Element subElement = null;
50 for (int i = 0; i < nl.getLength(); i++) {
51 Node node = nl.item(i);
52 //子元素不是description和meta属性 53 if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT) &&
54 !nodeNameEquals(node, META_ELEMENT)) {
55 if (subElement != null) {
56 error(elementName + " must not contain more than one sub-element", ele);
57 }
58 else {//当前<property>元素包含有子元素 59 subElement = (Element) node;
60 }
61 }
62 }
63 //判断property的属性值是ref还是value，不允许既是ref又是value 64 boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE);
65 boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE);
66 if ((hasRefAttribute && hasValueAttribute) ||
67 ((hasRefAttribute || hasValueAttribute) && subElement != null)) {
68 error(elementName +
69 " is only allowed to contain either 'ref' attribute OR 'value' attribute OR sub-element", ele);
70 }
71 //如果属性是ref，创建一个ref的数据对象RuntimeBeanReference，这个对象 72 //封装了ref信息 73 if (hasRefAttribute) {
74 String refName = ele.getAttribute(REF_ATTRIBUTE);
75 if (!StringUtils.hasText(refName)) {
76 error(elementName + " contains empty 'ref' attribute", ele);
77 }
78 //一个指向运行时所依赖对象的引用 79 RuntimeBeanReference ref = new RuntimeBeanReference(refName);
80 //设置这个ref的数据对象是被当前的property对象所引用 81 ref.setSource(extractSource(ele));
82 return ref;
83 }
84 //如果属性是value，创建一个value的数据对象TypedStringValue，这个对象 85 //封装了value信息 86 else if (hasValueAttribute) {
87 //一个持有String类型值的对象 88 TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE));
89 //设置这个value数据对象是被当前的property对象所引用 90 valueHolder.setSource(extractSource(ele));
91 return valueHolder;
92 }
93 //如果当前<property>元素还有子元素 94 else if (subElement != null) {
95 //解析<property>的子元素 96 return parsePropertySubElement(subElement, bd);
97 }
98 else {
99 //propery属性中既不是ref，也不是value属性，解析出错返回null error(elementName + " must specify a ref or value", ele); 100 return null;
101 }
}

1 //解析<property>元素中ref,value或者集合等子元素
2 public Object parsePropertySubElement(Element ele, BeanDefinition bd, String defaultValueType) {
3 //如果<property>没有使用Spring默认的命名空间，则使用用户自定义的规则解析//内嵌元素 4 if (!isDefaultNamespace(ele)) {
5 return parseNestedCustomElement(ele, bd);
6 }
7 //如果子元素是bean，则使用解析<Bean>元素的方法解析 8 else if (nodeNameEquals(ele, BEAN_ELEMENT)) {
9 BeanDefinitionHolder nestedBd = parseBeanDefinitionElement(ele, bd);
10 if (nestedBd != null) {
11 nestedBd = decorateBeanDefinitionIfRequired(ele, nestedBd, bd);
12 }
13 return nestedBd;
14 }
15 //如果子元素是ref，ref中只能有以下3个属性：bean、local、parent 16 else if (nodeNameEquals(ele, REF_ELEMENT)) {
17 //获取<property>元素中的bean属性值，引用其他解析的Bean的名称 18 //可以不再同一个Spring配置文件中，具体请参考Spring对ref的配置规则 19 String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE);
20 boolean toParent = false;
21 if (!StringUtils.hasLength(refName)) {
22 //获取<property>元素中的local属性值，引用同一个Xml文件中配置 23 //的Bean的id，local和ref不同，local只能引用同一个配置文件中的Bean 24 refName = ele.getAttribute(LOCAL_REF_ATTRIBUTE);
25 if (!StringUtils.hasLength(refName)) {
26 //获取<property>元素中parent属性值，引用父级容器中的Bean 27 refName = ele.getAttribute(PARENT_REF_ATTRIBUTE);
28 toParent = true;
29 if (!StringUtils.hasLength(refName)) {
30 error("'bean', 'local' or 'parent' is required for <ref> element", ele);
31 return null;
32 }
33 }
34 }
35 //没有配置ref的目标属性值 36 if (!StringUtils.hasText(refName)) {
37 error("<ref> element contains empty target attribute", ele);
38 return null;
39 }
40 //创建ref类型数据，指向被引用的对象 41 RuntimeBeanReference ref = new RuntimeBeanReference(refName, toParent);
42 //设置引用类型值是被当前子元素所引用 43 ref.setSource(extractSource(ele));
44 return ref;
45 }
46 //如果子元素是<idref>，使用解析ref元素的方法解析 47 else if (nodeNameEquals(ele, IDREF_ELEMENT)) {
48 return parseIdRefElement(ele);
49 }
50 //如果子元素是<value>，使用解析value元素的方法解析 51 else if (nodeNameEquals(ele, VALUE_ELEMENT)) {
52 return parseValueElement(ele, defaultValueType);
53 }
54 //如果子元素是null，为<property>设置一个封装null值的字符串数据 55 else if (nodeNameEquals(ele, NULL_ELEMENT)) {
56 TypedStringValue nullHolder = new TypedStringValue(null);
57 nullHolder.setSource(extractSource(ele));
58 return nullHolder;
59 }
60 //如果子元素是<array>，使用解析array集合子元素的方法解析 61 else if (nodeNameEquals(ele, ARRAY_ELEMENT)) {
62 return parseArrayElement(ele, bd);
63 }
64 //如果子元素是<list>，使用解析list集合子元素的方法解析 65 else if (nodeNameEquals(ele, LIST_ELEMENT)) {
66 return parseListElement(ele, bd);
67 }
68 //如果子元素是<set>，使用解析set集合子元素的方法解析 69 else if (nodeNameEquals(ele, SET_ELEMENT)) {
70 return parseSetElement(ele, bd);
71 }
72 //如果子元素是<map>，使用解析map集合子元素的方法解析 73 else if (nodeNameEquals(ele, MAP_ELEMENT)) {
74 return parseMapElement(ele, bd);
75 }
76 //如果子元素是<props>，使用解析props集合子元素的方法解析 77 else if (nodeNameEquals(ele, PROPS_ELEMENT)) {
78 return parsePropsElement(ele);
79 }
80 //既不是ref，又不是value，也不是集合，则子元素配置错误，返回null 81 else {
82 error("Unknown property sub-element: [" + ele.getNodeName() + "]", ele);
83 return null;
84 }
}

1 //解析<list>集合子元素
2 public List parseListElement(Element collectionEle, BeanDefinition bd) {
3 //获取<list>元素中的value-type属性，即获取集合元素的数据类型 4 String defaultElementType = collectionEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
5 //获取<list>集合元素中的所有子节点 6 NodeList nl = collectionEle.getChildNodes();
7 //Spring中将List封装为ManagedList 8 ManagedList<Object> target = new ManagedList<Object>(nl.getLength());
9 target.setSource(extractSource(collectionEle));
10 //设置集合目标数据类型 11 target.setElementTypeName(defaultElementType);
12 target.setMergeEnabled(parseMergeAttribute(collectionEle));
13 //具体的<list>元素解析 14 parseCollectionElements(nl, target, bd, defaultElementType);
15 return target;
16 }
17 //具体解析<list>集合元素，<array>、<list>和<set>都使用该方法解析
18 protected void parseCollectionElements(
19 NodeList elementNodes, Collection<Object> target, BeanDefinition bd, String defaultElementType) {
20 //遍历集合所有节点 21 for (int i = 0; i < elementNodes.getLength(); i++) {
22 Node node = elementNodes.item(i);
23 //节点不是description节点 24 if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT)) {
25 //将解析的元素加入集合中，递归调用下一个子元素 26 target.add(parsePropertySubElement((Element) node, bd, defaultElementType));
27 }
28 }
}

//将解析的BeanDefinitionHold注册到容器中 public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
//获取解析的BeanDefinition的名称
String beanName = definitionHolder.getBeanName();
//向IoC容器注册BeanDefinition registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
//如果解析的BeanDefinition有别名，向容器为其注册别名
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String aliase : aliases) {
registry.registerAlias(beanName, aliase);
}
}
}

1 //存储注册的俄BeanDefinition
2 private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();
3 //向IoC容器注册解析的BeanDefiniton
4 public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
5 throws BeanDefinitionStoreException {
6 Assert.hasText(beanName, "Bean name must not be empty");
7 Assert.notNull(beanDefinition, "BeanDefinition must not be null");
8 //校验解析的BeanDefiniton 9 if (beanDefinition instanceof AbstractBeanDefinition) {
10 try {
11 ((AbstractBeanDefinition) beanDefinition).validate();
12 }
13 catch (BeanDefinitionValidationException ex) {
14 throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
15 "Validation of bean definition failed", ex);
16 }
17 }
18 //注册的过程中需要线程同步，以保证数据的一致性 19 synchronized (this.beanDefinitionMap) {
20 Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
21 //检查是否有同名的BeanDefinition已经在IoC容器中注册，如果已经注册， 22 //并且不允许覆盖已注册的Bean，则抛出注册失败异常 23 if (oldBeanDefinition != null) {
24 if (!this.allowBeanDefinitionOverriding) {
25 throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
26 "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
27 "': There is already [" + oldBeanDefinition + "] bound.");
28 }
29 else {//如果允许覆盖，则同名的Bean，后注册的覆盖先注册的 30 if (this.logger.isInfoEnabled()) {
31 this.logger.info("Overriding bean definition for bean '" + beanName +
32 "': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
33 }
34 }
35 }
36 //IoC容器中没有已经注册同名的Bean，按正常注册流程注册 37 else {
38 this.beanDefinitionNames.add(beanName);
39 this.frozenBeanDefinitionNames = null;
40 }
41 this.beanDefinitionMap.put(beanName, beanDefinition);
42 //重置所有已经注册过的BeanDefinition的缓存 43 resetBeanDefinition(beanName);
44 }
}

四、IOC容器的依赖注入

1 //获取IoC容器中指定名称的Bean
2 public Object getBean(String name) throws BeansException {
3 //doGetBean才是真正向IoC容器获取被管理Bean的过程 4 return doGetBean(name, null, null, false);
5 }
6 //获取IoC容器中指定名称和类型的Bean 7 public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
8 //doGetBean才是真正向IoC容器获取被管理Bean的过程 9 return doGetBean(name, requiredType, null, false);
10 }
11 //获取IoC容器中指定名称和参数的Bean 12 public Object getBean(String name, Object... args) throws BeansException {
13 //doGetBean才是真正向IoC容器获取被管理Bean的过程 14 return doGetBean(name, null, args, false);
15 }
16 //获取IoC容器中指定名称、类型和参数的Bean 17 public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException {
18 //doGetBean才是真正向IoC容器获取被管理Bean的过程 19 return doGetBean(name, requiredType, args, false);
20 }
21 //真正实现向IoC容器获取Bean的功能，也是触发依赖注入功能的地方 22 @SuppressWarnings("unchecked")
23 protected <T> T doGetBean(
24 final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
25 throws BeansException {
26 //根据指定的名称获取被管理Bean的名称，剥离指定名称中对容器的相关依赖 27 //如果指定的是别名，将别名转换为规范的Bean名称 28 final String beanName = transformedBeanName(name);
29 Object bean;
30 //先从缓存中取是否已经有被创建过的单态类型的Bean，对于单态模式的Bean整 31 //个IoC容器中只创建一次，不需要重复创建 32 Object sharedInstance = getSingleton(beanName);
33 //IoC容器创建单态模式Bean实例对象 34 if (sharedInstance != null && args == null) {
35 if (logger.isDebugEnabled()) {
36 //如果指定名称的Bean在容器中已有单态模式的Bean被创建，直接返回 37 //已经创建的Bean 38 if (isSingletonCurrentlyInCreation(beanName)) {
39 logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
40 "' that is not fully initialized yet - a consequence of a circular reference");
41 }
42 else {
43 logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
44 }
45 }
46 //获取给定Bean的实例对象，主要是完成FactoryBean的相关处理 47 //注意：BeanFactory是管理容器中Bean的工厂，而FactoryBean是 48 //创建创建对象的工厂Bean，两者之间有区别 49 bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
50 }
51 else {//缓存没有正在创建的单态模式Bean 52 //缓存中已经有已经创建的原型模式Bean，但是由于循环引用的问题导致实 53 //例化对象失败 54 if (isPrototypeCurrentlyInCreation(beanName)) {
55 throw new BeanCurrentlyInCreationException(beanName);
56 }
57 //对IoC容器中是否存在指定名称的BeanDefinition进行检查，首先检查是否 58 //能在当前的BeanFactory中获取的所需要的Bean，如果不能则委托当前容器 59 //的父级容器去查找，如果还是找不到则沿着容器的继承体系向父级容器查找 60 BeanFactory parentBeanFactory = getParentBeanFactory();
61 //当前容器的父级容器存在，且当前容器中不存在指定名称的Bean 62 if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
63 //解析指定Bean名称的原始名称 64 String nameToLookup = originalBeanName(name);
65 if (args != null) {
66 //委派父级容器根据指定名称和显式的参数查找 67 return (T) parentBeanFactory.getBean(nameToLookup, args);
68 }
69 else {
70 //委派父级容器根据指定名称和类型查找 71 return parentBeanFactory.getBean(nameToLookup, requiredType);
72 }
73 }
74 //创建的Bean是否需要进行类型验证，一般不需要 75 if (!typeCheckOnly) {
76 //向容器标记指定的Bean已经被创建 77 markBeanAsCreated(beanName);
78 }
79 //根据指定Bean名称获取其父级的Bean定义，主要解决Bean继承时子类 80 //合并父类公共属性问题 81 final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
82 checkMergedBeanDefinition(mbd, beanName, args);
83 //获取当前Bean所有依赖Bean的名称 84 String[] dependsOn = mbd.getDependsOn();
85 //如果当前Bean有依赖Bean 86 if (dependsOn != null) {
87 for (String dependsOnBean : dependsOn) {
88 //递归调用getBean方法，获取当前Bean的依赖Bean 89 getBean(dependsOnBean);
90 //把被依赖Bean注册给当前依赖的Bean 91 registerDependentBean(dependsOnBean, beanName);
92 }
93 }
94 //创建单态模式Bean的实例对象 95 if (mbd.isSingleton()) {
96 //这里使用了一个匿名内部类，创建Bean实例对象，并且注册给所依赖的对象 97 sharedInstance = getSingleton(beanName, new ObjectFactory() {
98 public Object getObject() throws BeansException {
99 try {
100 //创建一个指定Bean实例对象，如果有父级继承，则合并子//类和父类的定义 101 return createBean(beanName, mbd, args);
102 }
103 catch (BeansException ex) {
104 //显式地从容器单态模式Bean缓存中清除实例对象 105 destroySingleton(beanName);
106 throw ex;
107 }
108 }
109 });
110 //获取给定Bean的实例对象 111 bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
112 }
113 //IoC容器创建原型模式Bean实例对象 114 else if (mbd.isPrototype()) {
115 //原型模式(Prototype)是每次都会创建一个新的对象 116 Object prototypeInstance = null;
117 try {
118 //回调beforePrototypeCreation方法，默认的功能是注册当前创//建的原型对象 119 beforePrototypeCreation(beanName);
120 //创建指定Bean对象实例 121 prototypeInstance = createBean(beanName, mbd, args);
122 }
123 finally {
124 //回调afterPrototypeCreation方法，默认的功能告诉IoC容器指//定Bean的原型对象不再创建了 125 afterPrototypeCreation(beanName);
126 }
127 //获取给定Bean的实例对象 128 bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
129 }
130 //要创建的Bean既不是单态模式，也不是原型模式，则根据Bean定义资源中 131 //配置的生命周期范围，选择实例化Bean的合适方法，这种在Web应用程序中 132 //比较常用，如：request、session、application等生命周期 133 else {
134 String scopeName = mbd.getScope();
135 final Scope scope = this.scopes.get(scopeName);
136 //Bean定义资源中没有配置生命周期范围，则Bean定义不合法 137 if (scope == null) {
138 throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
139 }
140 try {
141 //这里又使用了一个匿名内部类，获取一个指定生命周期范围的实例 142 Object scopedInstance = scope.get(beanName, new ObjectFactory() {
143 public Object getObject() throws BeansException {
144 beforePrototypeCreation(beanName);
145 try {
146 return createBean(beanName, mbd, args);
147 }
148 finally {
149 afterPrototypeCreation(beanName);
150 }
151 }
152 });
153 //获取给定Bean的实例对象 154 bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
155 }
156 catch (IllegalStateException ex) {
157 throw new BeanCreationException(beanName,
158 "Scope '" + scopeName + "' is not active for the current thread; " +
159 "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton",
160 ex);
161 }
162 }
163 }
164 //对创建的Bean实例对象进行类型检查 165 if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
166 throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
167 }
168 return (T) bean;
169 }

1 //创建Bean实例对象
2 protected Object createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
3 throws BeanCreationException {
4 if (logger.isDebugEnabled()) {
5 logger.debug("Creating instance of bean '" + beanName + "'");
6 }
7 //判断需要创建的Bean是否可以实例化，即是否可以通过当前的类加载器加载 8 resolveBeanClass(mbd, beanName);
9 //校验和准备Bean中的方法覆盖 10 try {
11 mbd.prepareMethodOverrides();
12 }
13 catch (BeanDefinitionValidationException ex) {
14 throw new BeanDefinitionStoreException(mbd.getResourceDescription(),
15 beanName, "Validation of method overrides failed", ex);
16 }
17 try {
18 //如果Bean配置了初始化前和初始化后的处理器，则试图返回一个需要创建//Bean的代理对象 19 Object bean = resolveBeforeInstantiation(beanName, mbd);
20 if (bean != null) {
21 return bean;
22 }
23 }
24 catch (Throwable ex) {
25 throw new BeanCreationException(mbd.getResourceDescription(), beanName,
26 "BeanPostProcessor before instantiation of bean failed", ex);
27 }
28 //创建Bean的入口 29 Object beanInstance = doCreateBean(beanName, mbd, args);
30 if (logger.isDebugEnabled()) {
31 logger.debug("Finished creating instance of bean '" + beanName + "'");
32 }
33 return beanInstance;
34 }
35 //真正创建Bean的方法
36 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {
37 //封装被创建的Bean对象 38 BeanWrapper instanceWrapper = null;
39 if (mbd.isSingleton()){//单态模式的Bean，先从容器中缓存中获取同名Bean 40 instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
41 }
42 if (instanceWrapper == null) {
43 //创建实例对象 44 instanceWrapper = createBeanInstance(beanName, mbd, args);
45 }
46 final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
47 //获取实例化对象的类型 48 Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
49 //调用PostProcessor后置处理器 50 synchronized (mbd.postProcessingLock) {
51 if (!mbd.postProcessed) {
52 applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
53 mbd.postProcessed = true;
54 }
55 }
56 // Eagerly cache singletons to be able to resolve circular references 57 //向容器中缓存单态模式的Bean对象，以防循环引用 58 boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
59 isSingletonCurrentlyInCreation(beanName));
60 if (earlySingletonExposure) {
61 if (logger.isDebugEnabled()) {
62 logger.debug("Eagerly caching bean '" + beanName +
63 "' to allow for resolving potential circular references");
64 }
65 //这里是一个匿名内部类，为了防止循环引用，尽早持有对象的引用 66 addSingletonFactory(beanName, new ObjectFactory() {
67 public Object getObject() throws BeansException {
68 return getEarlyBeanReference(beanName, mbd, bean);
69 }
70 });
71 }
72 //Bean对象的初始化，依赖注入在此触发 73 //这个exposedObject在初始化完成之后返回作为依赖注入完成后的Bean 74 Object exposedObject = bean;
75 try {
76 //将Bean实例对象封装，并且Bean定义中配置的属性值赋值给实例对象 77 populateBean(beanName, mbd, instanceWrapper);
78 if (exposedObject != null) {
79 //初始化Bean对象 80 exposedObject = initializeBean(beanName, exposedObject, mbd);
81 }
82 }
83 catch (Throwable ex) {
84 if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
85 throw (BeanCreationException) ex;
86 }
87 else {
88 throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
89 }
90 }
91 if (earlySingletonExposure) {
92 //获取指定名称的已注册的单态模式Bean对象 93 Object earlySingletonReference = getSingleton(beanName, false);
94 if (earlySingletonReference != null) {
95 //根据名称获取的以注册的Bean和正在实例化的Bean是同一个 96 if (exposedObject == bean) {
97 //当前实例化的Bean初始化完成 98 exposedObject = earlySingletonReference;
99 }
100 //当前Bean依赖其他Bean，并且当发生循环引用时不允许新创建实例对象 101 else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
102 String[] dependentBeans = getDependentBeans(beanName);
103 Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
104 //获取当前Bean所依赖的其他Bean 105 for (String dependentBean : dependentBeans) {
106 //对依赖Bean进行类型检查 107 if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
108 actualDependentBeans.add(dependentBean);
109 }
110 }
111 if (!actualDependentBeans.isEmpty()) {
112 throw new BeanCurrentlyInCreationException(beanName,
113 "Bean with name '" + beanName + "' has been injected into other beans [" +
114 StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
115 "] in its raw version as part of a circular reference, but has eventually been " +
116 "wrapped. This means that said other beans do not use the final version of the " +
117 "bean. This is often the result of over-eager type matching - consider using " +
118 "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
119 }
120 }
121 }
122 }
123 //注册完成依赖注入的Bean 124 try {
125 registerDisposableBeanIfNecessary(beanName, bean, mbd);
126 }
127 catch (BeanDefinitionValidationException ex) {
128 throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
129 }
130 return exposedObject;
}

1 //创建Bean的实例对象
2 protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
3 //检查确认Bean是可实例化的 4 Class beanClass = resolveBeanClass(mbd, beanName);
5 //使用工厂方法对Bean进行实例化 6 if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
7 throw new BeanCreationException(mbd.getResourceDescription(), beanName,
8 "Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
9 }
10 if (mbd.getFactoryMethodName() != null) {
11 //调用工厂方法实例化 12 return instantiateUsingFactoryMethod(beanName, mbd, args);
13 }
14 //使用容器的自动装配方法进行实例化 15 boolean resolved = false;
16 boolean autowireNecessary = false;
17 if (args == null) {
18 synchronized (mbd.constructorArgumentLock) {
19 if (mbd.resolvedConstructorOrFactoryMethod != null) {
20 resolved = true;
21 autowireNecessary = mbd.constructorArgumentsResolved;
22 }
23 }
24 }
25 if (resolved) {
26 if (autowireNecessary) {
27 //配置了自动装配属性，使用容器的自动装配实例化 28 //容器的自动装配是根据参数类型匹配Bean的构造方法 29 return autowireConstructor(beanName, mbd, null, null);
30 }
31 else {
32 //使用默认的无参构造方法实例化 33 return instantiateBean(beanName, mbd);
34 }
35 }
36 //使用Bean的构造方法进行实例化 37 Constructor[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
38 if (ctors != null ||
39 mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
40 mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
41 //使用容器的自动装配特性，调用匹配的构造方法实例化 42 return autowireConstructor(beanName, mbd, ctors, args);
43 }
44 //使用默认的无参构造方法实例化 45 return instantiateBean(beanName, mbd);
46 }
47 //使用默认的无参构造方法实例化Bean对象
48 protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
49 try {
50 Object beanInstance;
51 final BeanFactory parent = this;
52 //获取系统的安全管理接口，JDK标准的安全管理API 53 if (System.getSecurityManager() != null) {
54 //这里是一个匿名内置类，根据实例化策略创建实例对象 55 beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
56 public Object run() {
57 return getInstantiationStrategy().instantiate(mbd, beanName, parent);
58 }
59 }, getAccessControlContext());
60 }
61 else {
62 //将实例化的对象封装起来 63 beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
64 }
65 BeanWrapper bw = new BeanWrapperImpl(beanInstance);
66 initBeanWrapper(bw);
67 return bw;
68 }
69 catch (Throwable ex) {
70 throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
71 }
72 }

1 //使用初始化策略实例化Bean对象
2 public Object instantiate(RootBeanDefinition beanDefinition, String beanName, BeanFactory owner) {
3 //如果Bean定义中没有方法覆盖，则就不需要CGLIB父类类的方法 4 if (beanDefinition.getMethodOverrides().isEmpty()) {
5 Constructor<?> constructorToUse;
6 synchronized (beanDefinition.constructorArgumentLock) {
7 //获取对象的构造方法或工厂方法 8 constructorToUse = (Constructor<?>) beanDefinition.resolvedConstructorOrFactoryMethod;
9 //如果没有构造方法且没有工厂方法 10 if (constructorToUse == null) {
11 //使用JDK的反射机制，判断要实例化的Bean是否是接口 12 final Class clazz = beanDefinition.getBeanClass();
13 if (clazz.isInterface()) {
14 throw new BeanInstantiationException(clazz, "Specified class is an interface");
15 }
16 try {
17 if (System.getSecurityManager() != null) {
18 //这里是一个匿名内置类，使用反射机制获取Bean的构造方法 19 constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor>() {
20 public Constructor run() throws Exception {
21 return clazz.getDeclaredConstructor((Class[]) null);
22 }
23 });
24 }
25 else {
26 constructorToUse = clazz.getDeclaredConstructor((Class[]) null);
27 }
28 beanDefinition.resolvedConstructorOrFactoryMethod = constructorToUse;
29 }
30 catch (Exception ex) {
31 throw new BeanInstantiationException(clazz, "No default constructor found", ex);
32 }
33 }
34 }
35 //使用BeanUtils实例化，通过反射机制调用”构造方法.newInstance(arg)”来进行实例化 36 return BeanUtils.instantiateClass(constructorToUse);
37 }
38 else {
39 //使用CGLIB来实例化对象 40 return instantiateWithMethodInjection(beanDefinition, beanName, owner);
41 }
}

1 //使用CGLIB进行Bean对象实例化
2 public Object instantiate(Constructor ctor, Object[] args) {
3 //CGLIB中的类 4 Enhancer enhancer = new Enhancer();
5 //将Bean本身作为其基类 6 enhancer.setSuperclass(this.beanDefinition.getBeanClass());
7 enhancer.setCallbackFilter(new CallbackFilterImpl());
8 enhancer.setCallbacks(new Callback[] {
9 NoOp.INSTANCE,
10 new LookupOverrideMethodInterceptor(),
11 new ReplaceOverrideMethodInterceptor()
12 });
13 //使用CGLIB的create方法生成实例对象 14 return (ctor == null) ?
15 enhancer.create() :
16 enhancer.create(ctor.getParameterTypes(), args);
17 }

1 //将Bean属性设置到生成的实例对象上
2 protected void populateBean(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw) {
3 //获取容器在解析Bean定义资源时为BeanDefiniton中设置的属性值 4 PropertyValues pvs = mbd.getPropertyValues();
5 //实例对象为null 6 if (bw == null) {
7 //属性值不为空 8 if (!pvs.isEmpty()) {
9 throw new BeanCreationException(
10 mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
11 }
12 else {
13 //实例对象为null，属性值也为空，不需要设置属性值，直接返回 14 return;
15 }
16 }
17 //在设置属性之前调用Bean的PostProcessor后置处理器 18 boolean continueWithPropertyPopulation = true;
19 if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
20 for (BeanPostProcessor bp : getBeanPostProcessors()) {
21 if (bp instanceof InstantiationAwareBeanPostProcessor) {
22 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
23 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
24 continueWithPropertyPopulation = false;
25 break;
26 }
27 }
28 }
29 }
30 if (!continueWithPropertyPopulation) {
31 return;
32 }
33 //依赖注入开始，首先处理autowire自动装配的注入 34 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
35 mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
36 MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
37 //对autowire自动装配的处理，根据Bean名称自动装配注入 38 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
39 autowireByName(beanName, mbd, bw, newPvs);
40 }
41 //根据Bean类型自动装配注入 42 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
43 autowireByType(beanName, mbd, bw, newPvs);
44 }
45 pvs = newPvs;
46 }
47 //检查容器是否持有用于处理单态模式Bean关闭时的后置处理器 48 boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
49 //Bean实例对象没有依赖，即没有继承基类 50 boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
51 if (hasInstAwareBpps || needsDepCheck) {
52 //从实例对象中提取属性描述符 53 PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw);
54 if (hasInstAwareBpps) {
55 for (BeanPostProcessor bp : getBeanPostProcessors()) {
56 if (bp instanceof InstantiationAwareBeanPostProcessor) {
57 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
58 //使用BeanPostProcessor处理器处理属性值 59 pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
60 if (pvs == null) {
61 return;
62 }
63 }
64 }
65 }
66 if (needsDepCheck) {
67 //为要设置的属性进行依赖检查 68 checkDependencies(beanName, mbd, filteredPds, pvs);
69 }
70 }
71 //对属性进行注入 72 applyPropertyValues(beanName, mbd, bw, pvs);
73 }
74 //解析并注入依赖属性的过程
75 protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
76 if (pvs == null || pvs.isEmpty()) {
77 return;
78 }
79 //封装属性值 80 MutablePropertyValues mpvs = null;
81 List<PropertyValue> original;
82 if (System.getSecurityManager()!= null) {
83 if (bw instanceof BeanWrapperImpl) {
84 //设置安全上下文，JDK安全机制 85 ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
86 }
87 }
88 if (pvs instanceof MutablePropertyValues) {
89 mpvs = (MutablePropertyValues) pvs;
90 //属性值已经转换 91 if (mpvs.isConverted()) {
92 try {
93 //为实例化对象设置属性值 94 bw.setPropertyValues(mpvs);
95 return;
96 }
97 catch (BeansException ex) {
98 throw new BeanCreationException(
99 mbd.getResourceDescription(), beanName, "Error setting property values", ex);
100 }
101 }
102 //获取属性值对象的原始类型值 103 original = mpvs.getPropertyValueList();
104 }
105 else {
106 original = Arrays.asList(pvs.getPropertyValues());
107 }
108 //获取用户自定义的类型转换 109 TypeConverter converter = getCustomTypeConverter();
110 if (converter == null) {
111 converter = bw;
112 }
113 //创建一个Bean定义属性值解析器，将Bean定义中的属性值解析为Bean实例对象 114 //的实际值 115 BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
116 //为属性的解析值创建一个拷贝，将拷贝的数据注入到实例对象中 117 List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size());
118 boolean resolveNecessary = false;
119 for (PropertyValue pv : original) {
120 //属性值不需要转换 121 if (pv.isConverted()) {
122 deepCopy.add(pv);
123 }
124 //属性值需要转换 125 else {
126 String propertyName = pv.getName();
127 //原始的属性值，即转换之前的属性值 128 Object originalValue = pv.getValue();
129 //转换属性值，例如将引用转换为IoC容器中实例化对象引用 130 Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
131 //转换之后的属性值 132 Object convertedValue = resolvedValue;
133 //属性值是否可以转换 134 boolean convertible = bw.isWritableProperty(propertyName) &&
135 !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
136 if (convertible) {
137 //使用用户自定义的类型转换器转换属性值 138 convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
139 }
140 //存储转换后的属性值，避免每次属性注入时的转换工作 141 if (resolvedValue == originalValue) {
142 if (convertible) {
143 //设置属性转换之后的值 144 pv.setConvertedValue(convertedValue);
145 }
146 deepCopy.add(pv);
147 }
148 //属性是可转换的，且属性原始值是字符串类型，且属性的原始类型值不是 149 //动态生成的字符串，且属性的原始值不是集合或者数组类型 150 else if (convertible && originalValue instanceof TypedStringValue &&
151 !((TypedStringValue) originalValue).isDynamic() &&
152 !(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
153 pv.setConvertedValue(convertedValue);
154 deepCopy.add(pv);
155 }
156 else {
157 resolveNecessary = true;
158 //重新封装属性的值 159 deepCopy.add(new PropertyValue(pv, convertedValue));
160 }
161 }
162 }
163 if (mpvs != null && !resolveNecessary) {
164 //标记属性值已经转换过 165 mpvs.setConverted();
166 }
167 //进行属性依赖注入 168 try {
169 bw.setPropertyValues(new MutablePropertyValues(deepCopy));
170 }
171 catch (BeansException ex) {
172 throw new BeanCreationException(
173 mbd.getResourceDescription(), beanName, "Error setting property values", ex);
174 }
}

1 //解析属性值，对注入类型进行转换
2 public Object resolveValueIfNecessary(Object argName, Object value) {
3 //对引用类型的属性进行解析 4 if (value instanceof RuntimeBeanReference) {
5 RuntimeBeanReference ref = (RuntimeBeanReference) value;
6 //调用引用类型属性的解析方法 7 return resolveReference(argName, ref);
8 }
9 //对属性值是引用容器中另一个Bean名称的解析 10 else if (value instanceof RuntimeBeanNameReference) {
11 String refName = ((RuntimeBeanNameReference) value).getBeanName();
12 refName = String.valueOf(evaluate(refName));
13 //从容器中获取指定名称的Bean 14 if (!this.beanFactory.containsBean(refName)) {
15 throw new BeanDefinitionStoreException(
16 "Invalid bean name '" + refName + "' in bean reference for " + argName);
17 }
18 return refName;
19 }
20 //对Bean类型属性的解析，主要是Bean中的内部类 21 else if (value instanceof BeanDefinitionHolder) {
22 BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value;
23 return resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition());
24 }
25 else if (value instanceof BeanDefinition) {
26 BeanDefinition bd = (BeanDefinition) value;
27 return resolveInnerBean(argName, "(inner bean)", bd);
28 }
29 //对集合数组类型的属性解析 30 else if (value instanceof ManagedArray) {
31 ManagedArray array = (ManagedArray) value;
32 //获取数组的类型 33 Class elementType = array.resolvedElementType;
34 if (elementType == null) {
35 //获取数组元素的类型 36 String elementTypeName = array.getElementTypeName();
37 if (StringUtils.hasText(elementTypeName)) {
38 try {
39 //使用反射机制创建指定类型的对象 40 elementType = ClassUtils.forName(elementTypeName, this.beanFactory.getBeanClassLoader());
41 array.resolvedElementType = elementType;
42 }
43 catch (Throwable ex) {
44 throw new BeanCreationException(
45 this.beanDefinition.getResourceDescription(), this.beanName,
46 "Error resolving array type for " + argName, ex);
47 }
48 }
49 //没有获取到数组的类型，也没有获取到数组元素的类型，则直接设置数 50 //组的类型为Object 51 else {
52 elementType = Object.class;
53 }
54 }
55 //创建指定类型的数组 56 return resolveManagedArray(argName, (List<?>) value, elementType);
57 }
58 //解析list类型的属性值 59 else if (value instanceof ManagedList) {
60 return resolveManagedList(argName, (List<?>) value);
61 }
62 //解析set类型的属性值 63 else if (value instanceof ManagedSet) {
64 return resolveManagedSet(argName, (Set<?>) value);
65 }
66 //解析map类型的属性值 67 else if (value instanceof ManagedMap) {
68 return resolveManagedMap(argName, (Map<?, ?>) value);
69 }
70 //解析props类型的属性值，props其实就是key和value均为字符串的map 71 else if (value instanceof ManagedProperties) {
72 Properties original = (Properties) value;
73 //创建一个拷贝，用于作为解析后的返回值 74 Properties copy = new Properties();
75 for (Map.Entry propEntry : original.entrySet()) {
76 Object propKey = propEntry.getKey();
77 Object propValue = propEntry.getValue();
78 if (propKey instanceof TypedStringValue) {
79 propKey = evaluate((TypedStringValue) propKey);
80 }
81 if (propValue instanceof TypedStringValue) {
82 propValue = evaluate((TypedStringValue) propValue);
83 }
84 copy.put(propKey, propValue);
85 }
86 return copy;
87 }
88 //解析字符串类型的属性值 89 else if (value instanceof TypedStringValue) {
90 TypedStringValue typedStringValue = (TypedStringValue) value;
91 Object valueObject = evaluate(typedStringValue);
92 try {
93 //获取属性的目标类型 94 Class<?> resolvedTargetType = resolveTargetType(typedStringValue);
95 if (resolvedTargetType != null) {
96 //对目标类型的属性进行解析，递归调用 97 return this.typeConverter.convertIfNecessary(valueObject, resolvedTargetType);
98 }
99 //没有获取到属性的目标对象，则按Object类型返回 100 else {
101 return valueObject;
102 }
103 }
104 catch (Throwable ex) {
105 throw new BeanCreationException(
106 this.beanDefinition.getResourceDescription(), this.beanName,
107 "Error converting typed String value for " + argName, ex);
108 }
109 }
110 else {
111 return evaluate(value);
112 }
113 }
114 //解析引用类型的属性值
115 private Object resolveReference(Object argName, RuntimeBeanReference ref) {
116 try {
117 //获取引用的Bean名称 118 String refName = ref.getBeanName();
119 refName = String.valueOf(evaluate(refName));
120 //如果引用的对象在父类容器中，则从父类容器中获取指定的引用对象 121 if (ref.isToParent()) {
122 if (this.beanFactory.getParentBeanFactory() == null) {
123 throw new BeanCreationException(
124 this.beanDefinition.getResourceDescription(), this.beanName,
125 "Can't resolve reference to bean '" + refName +
126 "' in parent factory: no parent factory available");
127 }
128 return this.beanFactory.getParentBeanFactory().getBean(refName);
129 }
130 //从当前的容器中获取指定的引用Bean对象，如果指定的Bean没有被实例化 131 //则会递归触发引用Bean的初始化和依赖注入 132 else {
133 Object bean = this.beanFactory.getBean(refName);
134 //将当前实例化对象的依赖引用对象 135 this.beanFactory.registerDependentBean(refName, this.beanName);
136 return bean;
137 }
138 }
139 catch (BeansException ex) {
140 throw new BeanCreationException(
141 this.beanDefinition.getResourceDescription(), this.beanName,
142 "Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex);
143 }
144 }
145 //解析array类型的属性
146 private Object resolveManagedArray(Object argName, List<?> ml, Class elementType) {
147 //创建一个指定类型的数组，用于存放和返回解析后的数组 148 Object resolved = Array.newInstance(elementType, ml.size());
149 for (int i = 0; i < ml.size(); i++) {
150 //递归解析array的每一个元素，并将解析后的值设置到resolved数组中，索引为i 151 Array.set(resolved, i,
152 resolveValueIfNecessary(new KeyedArgName(argName, i), ml.get(i)));
153 }
154 return resolved;
155 }
156 //解析list类型的属性 157 private List resolveManagedList(Object argName, List<?> ml) {
158 List<Object> resolved = new ArrayList<Object>(ml.size());
159 for (int i = 0; i < ml.size(); i++) {
160 //递归解析list的每一个元素 161 resolved.add(
162 resolveValueIfNecessary(new KeyedArgName(argName, i), ml.get(i)));
163 }
164 return resolved;
165 }
166 //解析set类型的属性 167 private Set resolveManagedSet(Object argName, Set<?> ms) {
168 Set<Object> resolved = new LinkedHashSet<Object>(ms.size());
169 int i = 0;
170 //递归解析set的每一个元素 171 for (Object m : ms) {
172 resolved.add(resolveValueIfNecessary(new KeyedArgName(argName, i), m));
173 i++;
174 }
175 return resolved;
176 }
177 //解析map类型的属性 178 private Map resolveManagedMap(Object argName, Map<?, ?> mm) {
179 Map<Object, Object> resolved = new LinkedHashMap<Object, Object>(mm.size());
180 //递归解析map中每一个元素的key和value 181 for (Map.Entry entry : mm.entrySet()) {
182 Object resolvedKey = resolveValueIfNecessary(argName, entry.getKey());
183 Object resolvedValue = resolveValueIfNecessary(
184 new KeyedArgName(argName, entry.getKey()), entry.getValue());
185 resolved.put(resolvedKey, resolvedValue);
186 }
187 return resolved;
188 }

1 //实现属性依赖注入功能
2 private void setPropertyValue(PropertyTokenHolder tokens, PropertyValue pv) throws BeansException {
3 //PropertyTokenHolder主要保存属性的名称、路径，以及集合的size等信息 4 String propertyName = tokens.canonicalName;
5 String actualName = tokens.actualName;
6 //keys是用来保存集合类型属性的size 7 if (tokens.keys != null) {
8 //将属性信息拷贝 9 PropertyTokenHolder getterTokens = new PropertyTokenHolder();
10 getterTokens.canonicalName = tokens.canonicalName;
11 getterTokens.actualName = tokens.actualName;
12 getterTokens.keys = new String[tokens.keys.length - 1];
13 System.arraycopy(tokens.keys, 0, getterTokens.keys, 0, tokens.keys.length - 1);
14 Object propValue;
15 try {
16 //获取属性值，该方法内部使用JDK的内省( Introspector)机制，调用属性//的getter(readerMethod)方法，获取属性的值 17 propValue = getPropertyValue(getterTokens);
18 }
19 catch (NotReadablePropertyException ex) {
20 throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
21 "Cannot access indexed value in property referenced " +
22 "in indexed property path '" + propertyName + "'", ex);
23 }
24 //获取集合类型属性的长度 25 String key = tokens.keys[tokens.keys.length - 1];
26 if (propValue == null) {
27 throw new NullValueInNestedPathException(getRootClass(), this.nestedPath + propertyName,
28 "Cannot access indexed value in property referenced " +
29 "in indexed property path '" + propertyName + "': returned null");
30 }
31 //注入array类型的属性值 32 else if (propValue.getClass().isArray()) {
33 //获取属性的描述符 34 PropertyDescriptor pd = getCachedIntrospectionResults().getPropertyDescriptor(actualName);
35 //获取数组的类型 36 Class requiredType = propValue.getClass().getComponentType();
37 //获取数组的长度 38 int arrayIndex = Integer.parseInt(key);
39 Object oldValue = null;
40 try {
41 //获取数组以前初始化的值 42 if (isExtractOldValueForEditor()) {
43 oldValue = Array.get(propValue, arrayIndex);
44 }
45 //将属性的值赋值给数组中的元素 46 Object convertedValue = convertIfNecessary(propertyName, oldValue, pv.getValue(), requiredType,
47 new PropertyTypeDescriptor(pd, new MethodParameter(pd.getReadMethod(), -1), requiredType));
48 Array.set(propValue, arrayIndex, convertedValue);
49 }
50 catch (IndexOutOfBoundsException ex) {
51 throw new InvalidPropertyException(getRootClass(), this.nestedPath + propertyName,
52 "Invalid array index in property path '" + propertyName + "'", ex);
53 }
54 }
55 //注入list类型的属性值 56 else if (propValue instanceof List) {
57 PropertyDescriptor pd = getCachedIntrospectionResults().getPropertyDescriptor(actualName);
58 //获取list集合的类型 59 Class requiredType = GenericCollectionTypeResolver.getCollectionReturnType(
60 pd.getReadMethod(), tokens.keys.length);
61 List list = (List) propValue;
62 //获取list集合的size 63 int index = Integer.parseInt(key);
64 Object oldValue = null;
65 if (isExtractOldValueForEditor() && index < list.size()) {
66 oldValue = list.get(index);
67 }
68 //获取list解析后的属性值 69 Object convertedValue = convertIfNecessary(propertyName, oldValue, pv.getValue(), requiredType,
70 new PropertyTypeDescriptor(pd, new MethodParameter(pd.getReadMethod(), -1), requiredType));
71 if (index < list.size()) {
72 //为list属性赋值 73 list.set(index, convertedValue);
74 }
75 //如果list的长度大于属性值的长度，则多余的元素赋值为null 76 else if (index >= list.size()) {
77 for (int i = list.size(); i < index; i++) {
78 try {
79 list.add(null);
80 }
81 catch (NullPointerException ex) {
82 throw new InvalidPropertyException(getRootClass(), this.nestedPath + propertyName,
83 "Cannot set element with index " + index + " in List of size " +
84 list.size() + ", accessed using property path '" + propertyName +
85 "': List does not support filling up gaps with null elements");
86 }
87 }
88 list.add(convertedValue);
89 }
90 }
91 //注入map类型的属性值 92 else if (propValue instanceof Map) {
93 PropertyDescriptor pd = getCachedIntrospectionResults().getPropertyDescriptor(actualName);
94 //获取map集合key的类型 95 Class mapKeyType = GenericCollectionTypeResolver.getMapKeyReturnType(
96 pd.getReadMethod(), tokens.keys.length);
97 //获取map集合value的类型 98 Class mapValueType = GenericCollectionTypeResolver.getMapValueReturnType(
99 pd.getReadMethod(), tokens.keys.length);
100 Map map = (Map) propValue;
101 //解析map类型属性key值 102 Object convertedMapKey = convertIfNecessary(null, null, key, mapKeyType,
103 new PropertyTypeDescriptor(pd, new MethodParameter(pd.getReadMethod(), -1), mapKeyType));
104 Object oldValue = null;
105 if (isExtractOldValueForEditor()) {
106 oldValue = map.get(convertedMapKey);
107 }
108 //解析map类型属性value值 109 Object convertedMapValue = convertIfNecessary(
110 propertyName, oldValue, pv.getValue(), mapValueType,
111 new TypeDescriptor(new MethodParameter(pd.getReadMethod(), -1, tokens.keys.length + 1)));
112 //将解析后的key和value值赋值给map集合属性 113 map.put(convertedMapKey, convertedMapValue);
114 }
115 else {
116 throw new InvalidPropertyException(getRootClass(), this.nestedPath + propertyName,
117 "Property referenced in indexed property path '" + propertyName +
118 "' is neither an array nor a List nor a Map; returned value was [" + pv.getValue() + "]");
119 }
120 }
121 //对非集合类型的属性注入 122 else {
123 PropertyDescriptor pd = pv.resolvedDescriptor;
124 if (pd == null || !pd.getWriteMethod().getDeclaringClass().isInstance(this.object)) {
125 pd = getCachedIntrospectionResults().getPropertyDescriptor(actualName);
126 //无法获取到属性名或者属性没有提供setter(写方法)方法 127 if (pd == null || pd.getWriteMethod() == null) {
128 //如果属性值是可选的，即不是必须的，则忽略该属性值 129 if (pv.isOptional()) {
130 logger.debug("Ignoring optional value for property '" + actualName +
131 "' - property not found on bean class [" + getRootClass().getName() + "]");
132 return;
133 }
134 //如果属性值是必须的，则抛出无法给属性赋值，因为每天提供setter方法异常 135 else {
136 PropertyMatches matches = PropertyMatches.forProperty(propertyName, getRootClass());
137 throw new NotWritablePropertyException(
138 getRootClass(), this.nestedPath + propertyName,
139 matches.buildErrorMessage(), matches.getPossibleMatches());
140 }
141 }
142 pv.getOriginalPropertyValue().resolvedDescriptor = pd;
143 }
144 Object oldValue = null;
145 try {
146 Object originalValue = pv.getValue();
147 Object valueToApply = originalValue;
148 if (!Boolean.FALSE.equals(pv.conversionNecessary)) {
149 if (pv.isConverted()) {
150 valueToApply = pv.getConvertedValue();
151 }
152 else {
153 if (isExtractOldValueForEditor() && pd.getReadMethod() != null) {
154 //获取属性的getter方法(读方法)，JDK内省机制 155 final Method readMethod = pd.getReadMethod();
156 //如果属性的getter方法不是public访问控制权限的，即访问控制权限比较严格， 157 //则使用JDK的反射机制强行访问非public的方法(暴力读取属性值) 158 if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers()) &&
159 !readMethod.isAccessible()) {
160 if (System.getSecurityManager()!= null) {
161 //匿名内部类，根据权限修改属性的读取控制限制 162 AccessController.doPrivileged(new PrivilegedAction<Object>() {
163 public Object run() {
164 readMethod.setAccessible(true);
165 return null;
166 }
167 });
168 }
169 else {
170 readMethod.setAccessible(true);
171 }
172 }
173 try {
174 //属性没有提供getter方法时，调用潜在的读取属性值//的方法，获取属性值 175 if (System.getSecurityManager() != null) {
176 oldValue = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
177 public Object run() throws Exception {
178 return readMethod.invoke(object);
179 }
180 }, acc);
181 }
182 else {
183 oldValue = readMethod.invoke(object);
184 }
185 }
186 catch (Exception ex) {
187 if (ex instanceof PrivilegedActionException) {
188 ex = ((PrivilegedActionException) ex).getException();
189 }
190 if (logger.isDebugEnabled()) {
191 logger.debug("Could not read previous value of property '" +
192 this.nestedPath + propertyName + "'", ex);
193 }
194 }
195 }
196 //设置属性的注入值 197 valueToApply = convertForProperty(propertyName, oldValue, originalValue, pd);
198 }
199 pv.getOriginalPropertyValue().conversionNecessary = (valueToApply != originalValue);
200 }
201 //根据JDK的内省机制，获取属性的setter(写方法)方法 202 final Method writeMethod = (pd instanceof GenericTypeAwarePropertyDescriptor ?
203 ((GenericTypeAwarePropertyDescriptor) pd).getWriteMethodForActualAccess() :
204 pd.getWriteMethod());
205 //如果属性的setter方法是非public，即访问控制权限比较严格，则使用JDK的反射机制， 206 //强行设置setter方法可访问(暴力为属性赋值) 207 if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers()) && !writeMethod.isAccessible()) {
208 //如果使用了JDK的安全机制，则需要权限验证 209 if (System.getSecurityManager()!= null) {
210 AccessController.doPrivileged(new PrivilegedAction<Object>() {
211 public Object run() {
212 writeMethod.setAccessible(true);
213 return null;
214 }
215 });
216 }
217 else {
218 writeMethod.setAccessible(true);
219 }
220 }
221 final Object value = valueToApply;
222 if (System.getSecurityManager() != null) {
223 try {
224 //将属性值设置到属性上去 225 AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
226 public Object run() throws Exception {
227 writeMethod.invoke(object, value);
228 return null;
229 }
230 }, acc);
231 }
232 catch (PrivilegedActionException ex) {
233 throw ex.getException();
234 }
235 }
236 else {
237 writeMethod.invoke(this.object, value);
238 }
239 }
240 catch (TypeMismatchException ex) {
241 throw ex;
242 }
243 catch (InvocationTargetException ex) {
244 PropertyChangeEvent propertyChangeEvent =
245 new PropertyChangeEvent(this.rootObject, this.nestedPath + propertyName, oldValue, pv.getValue());
246 if (ex.getTargetException() instanceof ClassCastException) {
247 throw new TypeMismatchException(propertyChangeEvent, pd.getPropertyType(), ex.getTargetException());
248 }
249 else {
250 throw new MethodInvocationException(propertyChangeEvent, ex.getTargetException());
251 }
252 }
253 catch (Exception ex) {
254 PropertyChangeEvent pce =
255 new PropertyChangeEvent(this.rootObject, this.nestedPath + propertyName, oldValue, pv.getValue());
256 throw new MethodInvocationException(pce, ex);
257 }
258 }
}

五、IoC容器的高级特性

1 //容器初始化的过程，读入Bean定义资源，并解析注册
2 public void refresh() throws BeansException, IllegalStateException {
3 synchronized (this.startupShutdownMonitor) {
4 //调用容器准备刷新的方法，获取容器的当时时间，同时给容器设置同步标识 5 prepareRefresh();
6 //告诉子类启动refreshBeanFactory()方法，Bean定义资源文件的载入从 7 //子类的refreshBeanFactory()方法启动 8 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
9 //为BeanFactory配置容器特性，例如类加载器、事件处理器等 10 prepareBeanFactory(beanFactory);
11 try {
12 //为容器的某些子类指定特殊的BeanPost事件处理器 13 postProcessBeanFactory(beanFactory);
14 //调用所有注册的BeanFactoryPostProcessor的Bean 15 invokeBeanFactoryPostProcessors(beanFactory);
16 //为BeanFactory注册BeanPost事件处理器. 17 //BeanPostProcessor是Bean后置处理器，用于监听容器触发的事件 18 registerBeanPostProcessors(beanFactory);
19 //初始化信息源，和国际化相关. 20 initMessageSource();
21 //初始化容器事件传播器. 22 initApplicationEventMulticaster();
23 //调用子类的某些特殊Bean初始化方法 24 onRefresh();
25 //为事件传播器注册事件监听器. 26 registerListeners();
27 //这里是对容器lazy-init属性进行处理的入口方法 28 finishBeanFactoryInitialization(beanFactory);
29 //初始化容器的生命周期事件处理器，并发布容器的生命周期事件 30 finishRefresh();
31 }
32 catch (BeansException ex) {
33 //销毁以创建的单态Bean 34 destroyBeans();
35 //取消refresh操作，重置容器的同步标识. 36 cancelRefresh(ex);
37 throw ex;
38 }
39 }
}

1 //对配置了lazy-init属性的Bean进行预实例化处理
2 protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
3 //这是Spring3以后新加的代码，为容器指定一个转换服务(ConversionService) 4 //在对某些Bean属性进行转换时使用
5 if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
6 beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
7 beanFactory.setConversionService(
8 beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
9 }
10 //为了类型匹配，停止使用临时的类加载器 11 beanFactory.setTempClassLoader(null);
12 //缓存容器中所有注册的BeanDefinition元数据，以防被修改 13 beanFactory.freezeConfiguration();
14 //对配置了lazy-init属性的单态模式Bean进行预实例化处理 15 beanFactory.preInstantiateSingletons();
}

1//对配置lazy-init属性单态Bean的预实例化
2public void preInstantiateSingletons() throws BeansException {
3 if (this.logger.isInfoEnabled()) {
4 this.logger.info("Pre-instantiating singletons in " + this);
5 }
6 //在对配置lazy-init属性单态Bean的预实例化过程中，必须多线程同步，以确保数据一致性 7 synchronized (this.beanDefinitionMap) {
8 for (String beanName : this.beanDefinitionNames) {
9 //获取指定名称的Bean定义 10 RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
11 //Bean不是抽象的，是单态模式的，且lazy-init属性配置为false 12 if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
13 //如果指定名称的bean是创建容器的Bean 14 if (isFactoryBean(beanName)) {
15 //FACTORY_BEAN_PREFIX=”&”，当Bean名称前面加”&”符号 16 //时，获取的是产生容器对象本身，而不是容器产生的Bean. 17 //调用getBean方法，触发容器对Bean实例化和依赖注入过程 18 final FactoryBean factory = (FactoryBean) getBean(FACTORY_BEAN_PREFIX + beanName);
19 //标识是否需要预实例化 20 boolean isEagerInit;
21 if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
22 //一个匿名内部类 23 isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
24 public Boolean run() {
25 return ((SmartFactoryBean) factory).isEagerInit();
26 }
27 }, getAccessControlContext());
28 }
29 else {
30 isEagerInit = factory instanceof SmartFactoryBean && ((SmartFactoryBean) factory).isEagerInit();
31 }
32 if (isEagerInit) {
33 //调用getBean方法，触发容器对Bean实例化和依赖注入过程 34 getBean(beanName);
35 }
36 }
37 else {
38 //调用getBean方法，触发容器对Bean实例化和依赖注入过程 39 getBean(beanName);
40 }
41 }
42 }
43 }
}

//工厂Bean，用于产生其他对象 public interface FactoryBean<T> {
//获取容器管理的对象实例 T getObject() throws Exception;
//获取Bean工厂创建的对象的类型
Class<?> getObjectType();
//Bean工厂创建的对象是否是单态模式，如果是单态模式，则整个容器中只有一个实例
//对象，每次请求都返回同一个实例对象 boolean isSingleton();
}

1 //真正实现向IoC容器获取Bean的功能，也是触发依赖注入功能的地方 2 @SuppressWarnings("unchecked")
3 protected <T> T doGetBean(
4 final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
5 throws BeansException {
6 //根据指定的名称获取被管理Bean的名称，剥离指定名称中对容器的相关依赖 7 //如果指定的是别名，将别名转换为规范的Bean名称 8 final String beanName = transformedBeanName(name);
9 Object bean;
10 //先从缓存中取是否已经有被创建过的单态类型的Bean，对于单态模式的Bean整 11 //个IoC容器中只创建一次，不需要重复创建 12 Object sharedInstance = getSingleton(beanName);
13 //IoC容器创建单态模式Bean实例对象 14 if (sharedInstance != null && args == null) {
15 if (logger.isDebugEnabled()) {
16 //如果指定名称的Bean在容器中已有单态模式的Bean被创建，直接返回 17 //已经创建的Bean 18 if (isSingletonCurrentlyInCreation(beanName)) {
19 logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
20 "' that is not fully initialized yet - a consequence of a circular reference");
21 }
22 else {
23 logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
24 }
25 }
26 //获取给定Bean的实例对象，主要是完成FactoryBean的相关处理 27 bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
28 }
29 ……
30 }
31 //获取给定Bean的实例对象，主要是完成FactoryBean的相关处理
32 protected Object getObjectForBeanInstance(
33 Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {
34 //容器已经得到了Bean实例对象，这个实例对象可能是一个普通的Bean，也可能是 35 //一个工厂Bean，如果是一个工厂Bean，则使用它创建一个Bean实例对象，如果 36 //调用本身就想获得一个容器的引用，则指定返回这个工厂Bean实例对象 37 //如果指定的名称是容器的解引用(dereference，即是对象本身而非内存地址)， 38 //且Bean实例也不是创建Bean实例对象的工厂Bean 39 if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
40 throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
41 }
42 //如果Bean实例不是工厂Bean，或者指定名称是容器的解引用，调用者向获取对 43 //容器的引用，则直接返回当前的Bean实例 44 if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
45 return beanInstance;
46 }
47 //处理指定名称不是容器的解引用，或者根据名称获取的Bean实例对象是一个工厂Bean 48 //使用工厂Bean创建一个Bean的实例对象 49 Object object = null;
50 if (mbd == null) {
51 //从Bean工厂缓存中获取给定名称的Bean实例对象 52 object = getCachedObjectForFactoryBean(beanName);
53 }
54 //让Bean工厂生产给定名称的Bean对象实例 55 if (object == null) {
56 FactoryBean factory = (FactoryBean) beanInstance;
57 //如果从Bean工厂生产的Bean是单态模式的，则缓存 58 if (mbd == null && containsBeanDefinition(beanName)) {
59 //从容器中获取指定名称的Bean定义，如果继承基类，则合并基类相关属性 60 mbd = getMergedLocalBeanDefinition(beanName);
61 }
62 //如果从容器得到Bean定义信息，并且Bean定义信息不是虚构的，则让工厂 63 //Bean生产Bean实例对象 64 boolean synthetic = (mbd != null && mbd.isSynthetic());
65 //调用FactoryBeanRegistrySupport类的getObjectFromFactoryBean 66 //方法，实现工厂Bean生产Bean对象实例的过程 67 object = getObjectFromFactoryBean(factory, beanName, !synthetic);
68 }
69 return object;
}

71 //Bean工厂生产Bean实例对象
72 protected Object getObjectFromFactoryBean(FactoryBean factory, String beanName, boolean shouldPostProcess) {
73 //Bean工厂是单态模式，并且Bean工厂缓存中存在指定名称的Bean实例对象 74 if (factory.isSingleton() && containsSingleton(beanName)) {
75 //多线程同步，以防止数据不一致 76 synchronized (getSingletonMutex()) {
77 //直接从Bean工厂缓存中获取指定名称的Bean实例对象 78 Object object = this.factoryBeanObjectCache.get(beanName);
79 //Bean工厂缓存中没有指定名称的实例对象，则生产该实例对象 80 if (object == null) {
81 //调用Bean工厂的getObject方法生产指定Bean的实例对象 82 object = doGetObjectFromFactoryBean(factory, beanName, shouldPostProcess);
83 //将生产的实例对象添加到Bean工厂缓存中 84 this.factoryBeanObjectCache.put(beanName, (object != null ? object : NULL_OBJECT));
85 }
86 return (object != NULL_OBJECT ? object : null);
87 }
88 }
89 //调用Bean工厂的getObject方法生产指定Bean的实例对象 90 else {
91 return doGetObjectFromFactoryBean(factory, beanName, shouldPostProcess);
92 }
93 }
94 //调用Bean工厂的getObject方法生产指定Bean的实例对象 95 private Object doGetObjectFromFactoryBean(
96 final FactoryBean factory, final String beanName, final boolean shouldPostProcess)
97 throws BeanCreationException {
98 Object object;
99 try {
100 if (System.getSecurityManager() != null) {
101 AccessControlContext acc = getAccessControlContext();
102 try {
103 //实现PrivilegedExceptionAction接口的匿名内置类 104 //根据JVM检查权限，然后决定BeanFactory创建实例对象 105 object = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
106 public Object run() throws Exception {
107 //调用BeanFactory接口实现类的创建对象方法 108 return factory.getObject();
109 }
110 }, acc);
111 }
112 catch (PrivilegedActionException pae) {
113 throw pae.getException();
114 }
115 }
116 else {
117 //调用BeanFactory接口实现类的创建对象方法 118 object = factory.getObject();
119 }
120 }
121 catch (FactoryBeanNotInitializedException ex) {
122 throw new BeanCurrentlyInCreationException(beanName, ex.toString());
123 }
124 catch (Throwable ex) {
125 throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
126 }
127 //创建出来的实例对象为null，或者因为单态对象正在创建而返回null 128 if (object == null && isSingletonCurrentlyInCreation(beanName)) {
129 throw new BeanCurrentlyInCreationException(
130 beanName, "FactoryBean which is currently in creation returned null from getObject");
131 }
132 //为创建出来的Bean实例对象添加BeanPostProcessor后置处理器 133 if (object != null && shouldPostProcess) {
134 try {
135 object = postProcessObjectFromFactoryBean(object, beanName);
136 }
137 catch (Throwable ex) {
138 throw new BeanCreationException(beanName, "Post-processing of the FactoryBean's object failed", ex);
139 }
140 }
141 return object;
}

143 public class AnnotationTestBeanFactory implements FactoryBean<IJmxTestBean> {
144 private final FactoryCreatedAnnotationTestBean instance = new FactoryCreatedAnnotationTestBean();
145 public AnnotationTestBeanFactory() {
146 this.instance.setName("FACTORY");
147 }
148 //AnnotationTestBeanFactory产生Bean实例对象的实现 149 public IJmxTestBean getObject() throws Exception {
150 return this.instance;
151 }
152 public Class<? extends IJmxTestBean> getObjectType() {
153 return FactoryCreatedAnnotationTestBean.class;
154 }
155 public boolean isSingleton() {
156 return true;
157 }
}

1 package org.springframework.beans.factory.config;
2 import org.springframework.beans.BeansException;
3 public interface BeanPostProcessor {
4 //为在Bean的初始化前提供回调入口 5 Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;
6 //为在Bean的初始化之后提供回调入口 7 Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;
}

1 //真正创建Bean的方法
2 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {
3 //创建Bean实例对象 4 ……
5 try {
6 //对Bean属性进行依赖注入 7 populateBean(beanName, mbd, instanceWrapper);
8 if (exposedObject != null) {
9 //在对Bean实例对象生成和依赖注入完成以后，开始对Bean实例对象 10 //进行初始化 ，为Bean实例对象应用BeanPostProcessor后置处理器 11 exposedObject = initializeBean(beanName, exposedObject, mbd);
12 }
13 }
14 catch (Throwable ex) {
15 if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
16 throw (BeanCreationException) ex;
17 }
18 ……
19 //为应用返回所需要的实例对象 20 return exposedObject;
}

1 //初始容器创建的Bean实例对象，为其添加BeanPostProcessor后置处理器
2 protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
3 //JDK的安全机制验证权限 4 if (System.getSecurityManager() != null) {
5 //实现PrivilegedAction接口的匿名内部类 6 AccessController.doPrivileged(new PrivilegedAction<Object>() {
7 public Object run() {
8 invokeAwareMethods(beanName, bean);
9 return null;
10 }
11 }, getAccessControlContext());
12 }
13 else {
14 //为Bean实例对象包装相关属性，如名称，类加载器，所属容器等信息 15 invokeAwareMethods(beanName, bean);
16 }
17 Object wrappedBean = bean;
18 //对BeanPostProcessor后置处理器的postProcessBeforeInitialization 19 //回调方法的调用，为Bean实例初始化前做一些处理 20 if (mbd == null || !mbd.isSynthetic()) {
21 wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
22 }
23 //调用Bean实例对象初始化的方法，这个初始化方法是在Spring Bean定义配置 24 //文件中通过init-method属性指定的 25 try {
26 invokeInitMethods(beanName, wrappedBean, mbd);
27 }
28 catch (Throwable ex) {
29 throw new BeanCreationException(
30 (mbd != null ? mbd.getResourceDescription() : null),
31 beanName, "Invocation of init method failed", ex);
32 }
33 //对BeanPostProcessor后置处理器的postProcessAfterInitialization 34 //回调方法的调用，为Bean实例初始化之后做一些处理 35 if (mbd == null || !mbd.isSynthetic()) {
36 wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
37 }
38 return wrappedBean;
39 }
40 //调用BeanPostProcessor后置处理器实例对象初始化之前的处理方法
41 public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
42 throws BeansException {
43 Object result = existingBean;
44 //遍历容器为所创建的Bean添加的所有BeanPostProcessor后置处理器 45 for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
46 //调用Bean实例所有的后置处理中的初始化前处理方法，为Bean实例对象在 47 //初始化之前做一些自定义的处理操作 48 result = beanProcessor.postProcessBeforeInitialization(result, beanName);
49 if (result == null) {
50 return result;
51 }
52 }
53 return result;
54 }
55 //调用BeanPostProcessor后置处理器实例对象初始化之后的处理方法 56 public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
57 throws BeansException {
58 Object result = existingBean;
59 //遍历容器为所创建的Bean添加的所有BeanPostProcessor后置处理器 60 for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
61 //调用Bean实例所有的后置处理中的初始化后处理方法，为Bean实例对象在 62 //初始化之后做一些自定义的处理操作 63 result = beanProcessor.postProcessAfterInitialization(result, beanName);
64 if (result == null) {
65 return result;
66 }
67 }
68 return result;
}

1 //为容器中管理的Bean注册一个面向切面编程的通知适配器
2 public class AdvisorAdapterRegistrationManager implements BeanPostProcessor {
3 //容器中负责管理切面通知适配器注册的对象 4 private AdvisorAdapterRegistry advisorAdapterRegistry = GlobalAdvisorAdapterRegistry.getInstance();
5 public void setAdvisorAdapterRegistry(AdvisorAdapterRegistry advisorAdapterRegistry) {
6 this.advisorAdapterRegistry = advisorAdapterRegistry;
7 }
8 //BeanPostProcessor在Bean对象初始化前的操作 9 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
10 //没有做任何操作，直接返回容器创建的Bean对象 11 return bean;
12 }
13 //BeanPostProcessor在Bean对象初始化后的操作 14 public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
15 if (bean instanceof AdvisorAdapter){
16 //如果容器创建的Bean实例对象是一个切面通知适配器，则向容器的注册
this.advisorAdapterRegistry.registerAdvisorAdapter((AdvisorAdapter) bean); 17 }
18 return bean;
19 }
}

1 protected void populateBean(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw) {
2 //获取Bean定义的属性值，并对属性值进行处理 3 PropertyValues pvs = mbd.getPropertyValues();
4 ……
5 //对依赖注入处理，首先处理autowiring自动装配的依赖注入 6 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
7 mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
8 MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
9 //根据Bean名称进行autowiring自动装配处理 10 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
11 autowireByName(beanName, mbd, bw, newPvs);
12 }
13 //根据Bean类型进行autowiring自动装配处理 14 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
15 autowireByType(beanName, mbd, bw, newPvs);
16 }
17 }
18 //对非autowiring的属性进行依赖注入处理 19 ……
}

1 //根据名称对属性进行自动依赖注入
2 protected void autowireByName(
3 String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {
4 //对Bean对象中非简单属性(不是简单继承的对象，如8中原始类型，字符串，URL等//都是简单属性)进行处理 5 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
6 for (String propertyName : propertyNames) {
7 //如果Spring IoC容器中包含指定名称的Bean 8 if (containsBean(propertyName)) {
9 //调用getBean方法向IoC容器索取指定名称的Bean实例，迭代触发属性的//初始化和依赖注入 10 Object bean = getBean(propertyName);
11 //为指定名称的属性赋予属性值 12 pvs.add(propertyName, bean);
13 //指定名称属性注册依赖Bean名称，进行属性依赖注入 14 registerDependentBean(propertyName, beanName);
15 if (logger.isDebugEnabled()) {
16 logger.debug("Added autowiring by name from bean name '" + beanName +
17 "' via property '" + propertyName + "' to bean named '" + propertyName + "'");
18 }
19 }
20 else {
21 if (logger.isTraceEnabled()) {
22 logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName +
23 "' by name: no matching bean found");
24 }
25 }
26 }
27 }
28 //根据类型对属性进行自动依赖注入
29 protected void autowireByType(
30 String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {
31 //获取用户定义的类型转换器 32 TypeConverter converter = getCustomTypeConverter();
33 if (converter == null) {
34 converter = bw;
35 }
36 //存放解析的要注入的属性 37 Set<String> autowiredBeanNames = new LinkedHashSet<String>(4);
38 //对Bean对象中非简单属性(不是简单继承的对象，如8中原始类型，字符 39 //URL等都是简单属性)进行处理 40 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
41 for (String propertyName : propertyNames) {
42 try {
43 //获取指定属性名称的属性描述器 44 PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
45 //不对Object类型的属性进行autowiring自动依赖注入 46 if (!Object.class.equals(pd.getPropertyType())) {
47 //获取属性的setter方法 48 MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
49 //检查指定类型是否可以被转换为目标对象的类型 50 boolean eager = !PriorityOrdered.class.isAssignableFrom(bw.getWrappedClass());
51 //创建一个要被注入的依赖描述 52 DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager);
53 //根据容器的Bean定义解析依赖关系，返回所有要被注入的Bean对象 54 Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter);
55 if (autowiredArgument != null) {
56 //为属性赋值所引用的对象 57 pvs.add(propertyName, autowiredArgument);
58 }
59 for (String autowiredBeanName : autowiredBeanNames) {
60 //指定名称属性注册依赖Bean名称，进行属性依赖注入 61 registerDependentBean(autowiredBeanName, beanName);
62 if (logger.isDebugEnabled()) {
63 logger.debug("Autowiring by type from bean name '" + beanName + "' via property '" +
64 propertyName + "' to bean named '" + autowiredBeanName + "'");
65 }
66 }
67 //释放已自动注入的属性 68 autowiredBeanNames.clear();
69 }
70 }
71 catch (BeansException ex) {
72 throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex);
73 }
74 }
}

1 //为指定的Bean注入依赖的Bean
2 public void registerDependentBean(String beanName, String dependentBeanName) {
3 //处理Bean名称，将别名转换为规范的Bean名称 4 String canonicalName = canonicalName(beanName);
5 //多线程同步，保证容器内数据的一致性 6 //先从容器中：bean名称-->全部依赖Bean名称集合找查找给定名称Bean的依赖Bean 7 synchronized (this.dependentBeanMap) {
8 //获取给定名称Bean的所有依赖Bean名称 9 Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
10 if (dependentBeans == null) {
11 //为Bean设置依赖Bean信息 12 dependentBeans = new LinkedHashSet<String>(8);
13 this.dependentBeanMap.put(canonicalName, dependentBeans);
14 }
15 //向容器中：bean名称-->全部依赖Bean名称集合添加Bean的依赖信息 16 //即，将Bean所依赖的Bean添加到容器的集合中 17 dependentBeans.add(dependentBeanName);
18 }
19 //从容器中：bean名称-->指定名称Bean的依赖Bean集合找查找给定名称 20 //Bean的依赖Bean 21 synchronized (this.dependenciesForBeanMap) {
22 Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(dependentBeanName);
23 if (dependenciesForBean == null) {
24 dependenciesForBean = new LinkedHashSet<String>(8);
25 this.dependenciesForBeanMap.put(dependentBeanName, dependenciesForBean);
26 }
27 //向容器中：bean名称-->指定Bean的依赖Bean名称集合添加Bean的依赖信息 28 //即，将Bean所依赖的Bean添加到容器的集合中 29 dependenciesForBean.add(canonicalName);
30 }
}