Spring 注解驱动（二）Servlet 3.0 注解驱动在 Spring MVC 中的应用

Spring 注解驱动（二）Servlet 3.0 注解驱动在 Spring MVC 中的应用

Spring 系列目录(https://www.cnblogs.com/binarylei/p/10198698.html)

在 Servlet 3.0 时支持注解启动，不再需要 web.xml 配制文件。详见《Servlet 3.0 规范（二）注解规范》：https://www.cnblogs.com/binarylei/p/10204208.html

一、Servlet 3.0 与 Spring MVC 整合

@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {
@Override
public void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
throws ServletException { List<WebApplicationInitializer> initializers = new LinkedList<>();
if (webAppInitializerClasses != null) {
for (Class<?> waiClass : webAppInitializerClasses) {
// WebApplicationInitializer 的实现类
if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
try {
initializers.add((WebApplicationInitializer)
ReflectionUtils.accessibleConstructor(waiClass).newInstance());
} catch (Throwable ex) {
throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
}
}
}
} if (initializers.isEmpty()) {
servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
return;
} // 执行 onStartup
AnnotationAwareOrderComparator.sort(initializers);
for (WebApplicationInitializer initializer : initializers) {
initializer.onStartup(servletContext);
}
}}


Spring MVC 启动时会调用 WebApplicationInitializer 实现类的 onStartup 方法启动 WEB 容器。WebApplicationInitializer 的继承关系如下：

WebApplicationInitializer
|- AbstractContextLoaderInitializer
|- AbstractDispatcherServletInitializer
|- AbstractAnnotationConfigDispatcherServletInitializer


• AbstractContextLoaderInitializer 创建 Root 根容器并注册 ContextLoaderListener，创建根容器由子类实现。核心方法：registerContextLoaderListener

• AbstractDispatcherServletInitializer 创建 Servlet 容器，并注册 DispatcherServlet 和 Filete，创建根容器由子类实现。核心方法：registerDispatcherServlet

• AbstractAnnotationConfigDispatcherServletInitializer 创建 Root 和 Servlet 容器。核心方法：createRootApplicationContext、createServletApplicationContext

断点调试，webAppInitializerClasses 有以下类，显然只有一个实现类 MyAbstractAnnotationConfigDispatcherServletInitializer 执行了 onStartup 方法。

0 = {Class@4467} "class org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer"
1 = {Class@4468} "class org.springframework.web.servlet.support.AbstractDispatcherServletInitializer"
2 = {Class@4469} "class org.springframework.web.server.adapter.AbstractReactiveWebInitializer"
3 = {Class@4470} "class org.springframework.web.context.AbstractContextLoaderInitializer"
4 = {Class@4471} "class com.github.binarylei.MyAbstractAnnotationConfigDispatcherServletInitializer"


二、WebMvcConfigurer 接管 xml 配置

(1) @EnableWebMvc

开启 Spring 高级功能，相当于 <mvc:annotation-driven/>

(2) WebMvcConfigurer

对应以前 XML 配置中的每一项，以 interceptors 为例，其余详见官方文档：Spring 注解配置类 WebMvcConfigurer(https://docs.spring.io/spring/docs/5.1.3.RELEASE/spring-framework-reference/web.html#mvc-config)

@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer { @Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new LocaleChangeInterceptor());
registry.addInterceptor(new ThemeChangeInterceptor()).addPathPatterns("/**").excludePathPatterns("/admin/**");
registry.addInterceptor(new SecurityInterceptor()).addPathPatterns("/secure/*");
}
}


以上代码相当于之前 XML 中的

<mvc:interceptors>
<bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor"/>
<mvc:interceptor>
<mvc:mapping path="/**"/>
<mvc:exclude-mapping path="/admin/**"/>
<bean class="org.springframework.web.servlet.theme.ThemeChangeInterceptor"/>
</mvc:interceptor>
<mvc:interceptor>
<mvc:mapping path="/secure/*"/>
<bean class="org.example.SecurityInterceptor"/>
</mvc:interceptor>
</mvc:interceptors>


三、模拟 Spring Boot 将 WEB 打成 jar 包运行

Spring 官方文档注解配置

使用 tomcat7-maven-plugin 插件模拟 Spring Boot。

(1) WebApplicationInitializer 实现类

public class MyAbstractAnnotationConfigDispatcherServletInitializer extends
AbstractAnnotationConfigDispatcherServletInitializer { // Root 容器配置
protected Class<?>[] getRootConfigClasses() {
return new Class[0];
} // Servlet 容器配置
protected Class<?>[] getServletConfigClasses() {
return new Class[]{MyServletConfig.class};
} // Servlet Mapping，取代 web.xml 中的 servlet-mapping 配置
protected String[] getServletMappings() {
return new String[]{"/"};
} // Filter 配置，取代 web.xml 中的 filter 配置
@Override
protected Filter[] getServletFilters() {
CharacterEncodingFilter encodingFilter = new CharacterEncodingFilter();
encodingFilter.setEncoding("utf-8");
encodingFilter.setForceRequestEncoding(true);
encodingFilter.setForceResponseEncoding(true); return new Filter[]{encodingFilter};
}
}// 取代 spring-mvc.xml 配制
@Configuration
@ComponentScan(basePackages = "com.github.binarylei",
excludeFilters = {@ComponentScan.Filter(type = FilterType.ANNOTATION, classes = Controller.class)})
public class MyRootConfig {
}// 取代 spring-context.xml 配制
@Configuration
@ComponentScan(basePackages = "com.github.binarylei",
includeFilters = {@ComponentScan.Filter(type = FilterType.ANNOTATION, classes = Controller.class)})
public class MyServletConfig { @Bean
public ViewResolver viewResolver(){
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setViewClass(JstlView.class);
viewResolver.setPrefix("/WEB-INF/view/");
viewResolver.setSuffix(".jsp");
return viewResolver;
}
}


(2) tomcat7-maven-plugin 配制

tomcat7-maven-plugin 官网：http://tomcat.apache.org/maven-plugin-2.1/executable-war-jar.html

<packaging>war</packaging>
<properties>
<spring.version>5.1.0.RELEASE</spring.version> <project.build.sourceEncoding>utf-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties><dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>jstl</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
</dependencies><build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.0</version>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.1</version>
<executions>
<execution>
<id>tomcat-run</id>
<goals>
<goal>exec-war-only</goal>
</goals>
<phase>package</phase>
<configuration>
<path>/</path>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>


(3) 运行

执行 mvn package 后生成了两个文件：spring-war-1.0.0.war 和 spring-war-1.0.0-war-exec.jar

# localhost:8080/
java -jar spring-war-1.0.0-war-exec.jar
# IDEA remote 调试时(suspend=y)
java -jar -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:5005 spring-war-1.0.0-war-exec.jar


tomcat 启动远程时报错：https://www.aliyun.com/jiaocheng/1443062.html

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每天用心记录一点点。内容也许不重要，但习惯很重要！