Spring MVC异常处理详解(转)

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https://docs.spring.io/spring-boot/docs/2.0.0.RELEASE/reference/htmlsingle/

下图中，我画出了Spring MVC中，跟异常处理相关的主要类和接口。

1.包含文件

• spring.xml
• messages_zh_CN.properties
• messages_en_US.properties
• ExceptionHandle.java
• XXController.java

2.文件内容

• spring.xml

  <mvc:annotation-driven validator="validator" >
<mvc:message-converters>
<ref bean="stringHttpMessageConverter" />
</mvc:message-converters>
</mvc:annotation-driven> <!--避免错误信息是乱码-->
<util:list id="messageConverters">
<ref bean="stringHttpMessageConverter" />
</util:list> <bean id="stringHttpMessageConverter"
class="org.springframework.http.converter.StringHttpMessageConverter">
<constructor-arg value="UTF-8" index="0"/>
<property name="supportedMediaTypes">
<list>
<!--项目中返回都是转成json格式的string，所以是text类型-->
<value>text/plain;charset=UTF-8</value>
<value>text/html;charset=UTF-8</value>
</list>
</property>
</bean> <bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
<property name="providerClass" value="org.hibernate.validator.HibernateValidator"/>
<property name="validationMessageSource" ref="messageSource"/>
</bean> <bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
<property name="basenames">
<list>
<value>classpath:messages</value> <value>classpath:org/hibernate/validator/ValidationMessages</value>
</list>
</property>
<property name="useCodeAsDefaultMessage" value="false"/>
<property name="defaultEncoding" value="UTF-8"/>
<property name="cacheSeconds" value="60"/>
</bean>

• messages_zh_CN.properties

  #注意了，如果你的启动jvm是local是US他会去读取messages_en_US.properties文件
#如果不存在，就不会解析{uname.null}
uname.null=用户名不能为空

• ExceptionHandle.java

  import java.util.stream.Collectors;
import lombok.extern.slf4j.Slf4j;
import org.springframework.validation.BindException;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
import
org.springframework.web.method.annotation.MethodArgumentTypeMismatchException;
import com.xx.customquery.exception.BusinessException;
import com.xx.customquery.exception.CommonMessageCode.SystemMessageCode;
import com.xx.customquery.util.Result;
@ControllerAdvice
@Slf4j
public class ExceptionHandle {
@ExceptionHandler(BindException.class)
@ResponseBody
public String processValidationError(BindException ex) {
log.error(ex.getMessage(), ex);
String result = ex
.getBindingResult()
.getAllErrors()
.stream()
.map(ObjectError::getDefaultMessage)
.collect(Collectors.joining(",")); return Result.returnParamFailResult(result);
} @ExceptionHandler(MethodArgumentTypeMismatchException.class)
@ResponseBody
public String processArgumentTypeMismatchException(MethodArgumentTypeMismatchException ex) {
log.error(ex.getMessage(), ex);
return Result.returnParamFailResult(ex.getMessage());
} @ExceptionHandler(BusinessException.class)
@ResponseBody
public String processBusinessException(BusinessException ex) {
log.error(ex.getMessage(), ex);
return Result.returnFailResult(ex);
} @ExceptionHandler(Throwable.class)
@ResponseBody
public String processException(Throwable ex) {
log.error(ex.getMessage(), ex);
return Result.returnFailResult(new BusinessException(SystemMessageCode.ERROR_SYSTEM));
}
}

• Result.java

  import com.google.gson.Gson;
import com.xx.customquery.exception.BusinessException;
public class Result<E> {
public final static int SUCCESS = 0;
public final static int FAIL = 999;
public final static int PARAM_FAIL = -1;
private final static Gson GSON = new GsonBuilder().disableHtmlEscaping().create(); public static String returnSuccResult(){
return GSON.toJson(new Result<String>(SUCCESS, "", ""));
}
public static String returnFailResult(String message){
return GSON.toJson(new Result<String>(FAIL, message, ""));
}
public static String returnParamFailResult(String message){
return GSON.toJson(new Result<String>(PARAM_FAIL, message, ""));
}
public static String returnFailResult(BusinessException exception){
return GSON.toJson(new Result<String>(exception.getCode(), exception.getMessage(), ""));
}
public static <T> String returnDataResult(T data){
return GSON.toJson(new Result<T>(SUCCESS, "", data));
} private int code;
private String message;
private E data;
public Result(){}
public Result(int code,String message, E data){
this.code = code;
this.message = message;
this.data = data;
}
public int getCode() {
return code;
}
public void setCode(int code) {
this.code = code;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public E getData() {
return data;
}
public void setData(E data) {
this.data = data;
}
}

• XXController.java

  @ResponseBody
@RequestMapping(value = "save", method = RequestMethod.POST)
public String saveQuery(@Valid Query querys) {
}

• Query

  import lombok.Data;
import org.hibernate.validator.constraints.NotBlank;
@Data
public class Queries {
private long id;
@NotBlank(message="{uname.null}")
private String user;
}

http://www.jianshu.com/p/1390dc477d92

@ControllerAdvice源码

package org.springframework.web.bind.annotation;import java.lang.annotation.Annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;import org.springframework.core.annotation.AliasFor;
import org.springframework.stereotype.Component;@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface ControllerAdvice { @AliasFor("basePackages")
String[] value() default {};
@AliasFor("value")
String[] basePackages() default {};
Class<?>[] basePackageClasses() default {};
Class<?>[] assignableTypes() default {};
Class<? extends Annotation>[] annotations() default {};}

源码分析

@ ControllerAdvice是一个@ Component，
用于定义@ ExceptionHandler的，@InitBinder和@ModelAttribute方法，适用于所有使用@ RequestMapping方法，并处理所有@ RequestMapping标注方法出现异常的统一处理。

项目图片

这里写图片描述

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion> <groupId>com.jege.spring.boot</groupId>
<artifactId>spring-boot-controller-advice</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging> <name>spring-boot-controller-advice</name>
<url>http://maven.apache.org</url> <!-- 公共spring-boot配置，下面依赖jar文件不用在写版本号 -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.4.1.RELEASE</version>
<relativePath />
</parent> <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>1.8</java.version>
</properties> <dependencies> <!-- web -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency> <!-- 持久层 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency> <!-- h2内存数据库 -->
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency> <!-- 测试 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<!-- 只在test测试里面运行 -->
<scope>test</scope>
</dependency> </dependencies> <build>
<finalName>spring-boot-controller-advice</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
</configuration>
</plugin>
</plugins>
</build>
</project>

全局异常处理类CommonExceptionAdvice

package com.jege.spring.boot.exception;import java.util.Set;import javax.validation.ConstraintViolation;
import javax.validation.ConstraintViolationException;
import javax.validation.ValidationException;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.DataIntegrityViolationException;
import org.springframework.http.HttpStatus;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.validation.BindException;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.web.HttpMediaTypeNotSupportedException;
import org.springframework.web.HttpRequestMethodNotSupportedException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.ResponseStatus;import com.jege.spring.boot.json.AjaxResult;/**
* @author JE哥
* @email 1272434821@qq.com
* @description:全局异常处理
*/
@ControllerAdvice
@ResponseBody
public class CommonExceptionAdvice { private static Logger logger = LoggerFactory.getLogger(CommonExceptionAdvice.class); /**
* 400 - Bad Request
*/
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(MissingServletRequestParameterException.class)
public AjaxResult handleMissingServletRequestParameterException(MissingServletRequestParameterException e) {
logger.error("缺少请求参数", e);
return new AjaxResult().failure("required_parameter_is_not_present");
} /**
* 400 - Bad Request
*/
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(HttpMessageNotReadableException.class)
public AjaxResult handleHttpMessageNotReadableException(HttpMessageNotReadableException e) {
logger.error("参数解析失败", e);
return new AjaxResult().failure("could_not_read_json");
} /**
* 400 - Bad Request
*/
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(MethodArgumentNotValidException.class)
public AjaxResult handleMethodArgumentNotValidException(MethodArgumentNotValidException e) {
logger.error("参数验证失败", e);
BindingResult result = e.getBindingResult();
FieldError error = result.getFieldError();
String field = error.getField();
String code = error.getDefaultMessage();
String message = String.format("%s:%s", field, code);
return new AjaxResult().failure(message);
} /**
* 400 - Bad Request
*/
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(BindException.class)
public AjaxResult handleBindException(BindException e) {
logger.error("参数绑定失败", e);
BindingResult result = e.getBindingResult();
FieldError error = result.getFieldError();
String field = error.getField();
String code = error.getDefaultMessage();
String message = String.format("%s:%s", field, code);
return new AjaxResult().failure(message);
} /**
* 400 - Bad Request
*/
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(ConstraintViolationException.class)
public AjaxResult handleServiceException(ConstraintViolationException e) {
logger.error("参数验证失败", e);
Set<ConstraintViolation<?>> violations = e.getConstraintViolations();
ConstraintViolation<?> violation = violations.iterator().next();
String message = violation.getMessage();
return new AjaxResult().failure("parameter:" + message);
} /**
* 400 - Bad Request
*/
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(ValidationException.class)
public AjaxResult handleValidationException(ValidationException e) {
logger.error("参数验证失败", e);
return new AjaxResult().failure("validation_exception");
} /**
* 405 - Method Not Allowed
*/
@ResponseStatus(HttpStatus.METHOD_NOT_ALLOWED)
@ExceptionHandler(HttpRequestMethodNotSupportedException.class)
public AjaxResult handleHttpRequestMethodNotSupportedException(HttpRequestMethodNotSupportedException e) {
logger.error("不支持当前请求方法", e);
return new AjaxResult().failure("request_method_not_supported");
} /**
* 415 - Unsupported Media Type
*/
@ResponseStatus(HttpStatus.UNSUPPORTED_MEDIA_TYPE)
@ExceptionHandler(HttpMediaTypeNotSupportedException.class)
public AjaxResult handleHttpMediaTypeNotSupportedException(Exception e) {
logger.error("不支持当前媒体类型", e);
return new AjaxResult().failure("content_type_not_supported");
} /**
* 500 - Internal Server Error
*/
@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
@ExceptionHandler(ServiceException.class)
public AjaxResult handleServiceException(ServiceException e) {
logger.error("业务逻辑异常", e);
return new AjaxResult().failure("业务逻辑异常：" + e.getMessage());
} /**
* 500 - Internal Server Error
*/
@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
@ExceptionHandler(Exception.class)
public AjaxResult handleException(Exception e) {
logger.error("通用异常", e);
return new AjaxResult().failure("通用异常：" + e.getMessage());
} /**
* 操作数据库出现异常:名称重复，外键关联
*/
@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
@ExceptionHandler(DataIntegrityViolationException.class)
public AjaxResult handleException(DataIntegrityViolationException e) {
logger.error("操作数据库出现异常:", e);
return new AjaxResult().failure("操作数据库出现异常：字段重复、有外键关联等");
}
}

自定义异常ServiceException

package com.jege.spring.boot.exception;/**
* @author JE哥
* @email 1272434821@qq.com
* @description:自定义异常类
*/
public class ServiceException extends RuntimeException {
public ServiceException(String msg) {
super(msg);
}
}

不需要application.properties

控制器AdviceController

package com.jege.spring.boot.controller;import java.util.List;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import com.jege.spring.boot.exception.ServiceException;/**
* @author JE哥
* @email 1272434821@qq.com
* @description:全局异常处理演示入口
*/
@RestController
public class AdviceController { @RequestMapping("/hello1")
public String hello1() {
int i = 1 / 0;
return "hello";
} @RequestMapping("/hello2")
public String hello2(Long id) {
String string = null;
string.length();
return "hello";
} @RequestMapping("/hello3")
public List<String> hello3() {
throw new ServiceException("test");
}
}

访问

• http://localhost:8080/hello1
  {"meta":{"success":false,"message":"通用异常：/ by zero"},"data":null}
• http://localhost:8080/hello2
  {"meta":{"success":false,"message":"通用异常：null"},"data":null}
• http://localhost:8080/hello3
  {"meta":{"success":false,"message":"业务逻辑异常：test"},"data":null}

源码地址

https://github.com/je-ge/spring-boot

http://www.jianshu.com/p/5c5601789626

在Spring MVC中，所有用于处理在请求映射和请求处理过程中抛出的异常的类，都要实现HandlerExceptionResolver接口。AbstractHandlerExceptionResolver实现该接口和Orderd接口，是HandlerExceptionResolver类的实现的基类。ResponseStatusExceptionResolver等具体的异常处理类均在AbstractHandlerExceptionResolver之上，实现了具体的异常处理方式。一个基于Spring MVC的Web应用程序中，可以存在多个实现了HandlerExceptionResolver的异常处理类，他们的执行顺序，由其order属性决定, order值越小，越是优先执行, 在执行到第一个返回不是null的ModelAndView的Resolver时，不再执行后续的尚未执行的Resolver的异常处理方法。。

下面我逐个介绍一下SpringMVC提供的这些异常处理类的功能。

DefaultHandlerExceptionResolver

HandlerExceptionResolver接口的默认实现，基本上是Spring MVC内部使用，用来处理Spring定义的各种标准异常，将其转化为相对应的HTTP Status Code。其处理的异常类型有：

handleNoSuchRequestHandlingMethod
handleHttpRequestMethodNotSupported
handleHttpMediaTypeNotSupported
handleMissingServletRequestParameter
handleServletRequestBindingException
handleTypeMismatch
handleHttpMessageNotReadable
handleHttpMessageNotWritable
handleMethodArgumentNotValidException
handleMissingServletRequestParameter
handleMissingServletRequestPartException
handleBindException

ResponseStatusExceptionResolver

用来支持ResponseStatus的使用，处理使用了ResponseStatus注解的异常，根据注解的内容，返回相应的HTTP Status Code和内容给客户端。如果Web应用程序中配置了ResponseStatusExceptionResolver，那么我们就可以使用ResponseStatus注解来注解我们自己编写的异常类，并在Controller中抛出该异常类，之后ResponseStatusExceptionResolver就会自动帮我们处理剩下的工作。

这是一个自己编写的异常，用来表示订单不存在：

@ResponseStatus(value=HttpStatus.NOT_FOUND, reason="No such Order") // 404
public class OrderNotFoundException extends RuntimeException {
// ...
}

这是一个使用该异常的Controller方法：

@RequestMapping(value="/orders/{id}", method=GET)
public String showOrder(@PathVariable("id") long id, Model model) {
Order order = orderRepository.findOrderById(id);
if (order == null) throw new OrderNotFoundException(id);
model.addAttribute(order);
return "orderDetail";
}

这样，当OrderNotFoundException被抛出时，ResponseStatusExceptionResolver会返回给客户端一个HTTP Status Code为404的响应。

AnnotationMethodHandlerExceptionResolver和ExceptionHandlerExceptionResolver

用来支持ExceptionHandler注解，使用被ExceptionHandler注解所标记的方法来处理异常。其中AnnotationMethodHandlerExceptionResolver在3.0版本中开始提供，ExceptionHandlerExceptionResolver在3.1版本中开始提供，从3.2版本开始，Spring推荐使用ExceptionHandlerExceptionResolver。
如果配置了AnnotationMethodHandlerExceptionResolver和ExceptionHandlerExceptionResolver这两个异常处理bean之一，那么我们就可以使用ExceptionHandler注解来处理异常。

下面是几个ExceptionHandler注解的使用例子：

@Controller
public class ExceptionHandlingController { // @RequestHandler methods
... // 以下是异常处理方法 // 将DataIntegrityViolationException转化为Http Status Code为409的响应
@ResponseStatus(value=HttpStatus.CONFLICT, reason="Data integrity violation") // 409
@ExceptionHandler(DataIntegrityViolationException.class)
public void conflict() {
// Nothing to do
} // 针对SQLException和DataAccessException返回视图databaseError
@ExceptionHandler({SQLException.class,DataAccessException.class})
public String databaseError() {
// Nothing to do. Returns the logical view name of an error page, passed to
// the view-resolver(s) in usual way.
// Note that the exception is _not_ available to this view (it is not added to
// the model) but see "Extending ExceptionHandlerExceptionResolver" below.
return "databaseError";
} // 创建ModleAndView，将异常和请求的信息放入到Model中，指定视图名字，并返回该ModleAndView
@ExceptionHandler(Exception.class)
public ModelAndView handleError(HttpServletRequest req, Exception exception) {
logger.error("Request: " + req.getRequestURL() + " raised " + exception); ModelAndView mav = new ModelAndView();
mav.addObject("exception", exception);
mav.addObject("url", req.getRequestURL());
mav.setViewName("error");
return mav;
}
}

需要注意的是，上面例子中的ExceptionHandler方法的作用域，只是在本Controller类中。如果需要使用ExceptionHandler来处理全局的Exception，则需要使用ControllerAdvice注解。

@ControllerAdvice
class GlobalDefaultExceptionHandler {
public static final String DEFAULT_ERROR_VIEW = "error"; @ExceptionHandler(value = Exception.class)
public ModelAndView defaultErrorHandler(HttpServletRequest req, Exception e) throws Exception {
// 如果异常使用了ResponseStatus注解，那么重新抛出该异常，Spring框架会处理该异常。
if (AnnotationUtils.findAnnotation(e.getClass(), ResponseStatus.class) != null)
throw e; // 否则创建ModleAndView，处理该异常。
ModelAndView mav = new ModelAndView();
mav.addObject("exception", e);
mav.addObject("url", req.getRequestURL());
mav.setViewName(DEFAULT_ERROR_VIEW);
return mav;
}
}

SimpleMappingExceptionResolver

提供了将异常映射为视图的能力，高度可定制化。其提供的能力有：

1. 根据异常的类型，将异常映射到视图；
2. 可以为不符合处理条件没有被处理的异常，指定一个默认的错误返回；
3. 处理异常时，记录log信息；
4. 指定需要添加到Modle中的Exception属性，从而在视图中展示该属性。

@Configuration
@EnableWebMvc
public class MvcConfiguration extends WebMvcConfigurerAdapter {
@Bean(name="simpleMappingExceptionResolver")
public SimpleMappingExceptionResolver createSimpleMappingExceptionResolver() {
SimpleMappingExceptionResolver r = new SimpleMappingExceptionResolver(); Properties mappings = new Properties();
mappings.setProperty("DatabaseException", "databaseError");
mappings.setProperty("InvalidCreditCardException", "creditCardError"); r.setExceptionMappings(mappings); // 默认为空
r.setDefaultErrorView("error"); // 默认没有
r.setExceptionAttribute("ex");
r.setWarnLogCategory("example.MvcLogger");
return r;
}
...
}

自定义ExceptionResolver

Spring MVC的异常处理非常的灵活，如果提供的ExceptionResolver类不能满足使用，我们可以实现自己的异常处理类。可以通过继承SimpleMappingExceptionResolver来定制Mapping的方式和能力，也可以直接继承AbstractHandlerExceptionResolver来实现其它类型的异常处理类。

Spring MVC是如何创建和使用这些Resolver的？

首先看Spring MVC是怎么加载异常处理bean的。

1. Spring MVC有两种加载异常处理类的方式，一种是根据类型，这种情况下，会加载ApplicationContext下所有实现了ExceptionResolver接口的bean，并根据其order属性排序，依次调用；一种是根据名字，这种情况下会加载ApplicationContext下，名字为handlerExceptionResolver的bean。
2. 不管使用那种加载方式，如果在ApplicationContext中没有找到异常处理bean，那么Spring MVC会加载默认的异常处理bean。
3. 默认的异常处理bean定义在DispatcherServlet.properties中。

org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver,\
org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver

以下代码摘自ispatcherServlet，描述了异常处理类的加载过程：

/**
* Initialize the HandlerMappings used by this class.
* <p>If no HandlerMapping beans are defined in the BeanFactory for this namespace,
* we default to BeanNameUrlHandlerMapping.
*/
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
OrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
}// Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
}
}
}

然后看Spring MVC是怎么使用异常处理bean的。

1. Spring MVC把请求映射和处理过程放到try catch中，捕获到异常后，使用异常处理bean进行处理。
2. 所有异常处理bean按照order属性排序，在处理过程中，遇到第一个成功处理异常的异常处理bean之后，不再调用后续的异常处理bean。

以下代码摘自DispatcherServlet，描述了处理异常的过程。

/**
* Process the actual dispatching to the handler.
* <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
* The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
* to find the first that supports the handler class.
* <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
* themselves to decide which methods are acceptable.
* @param request current HTTP request
* @param response current HTTP response
* @throws Exception in case of any kind of processing failure
*/
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);try {
ModelAndView mv = null;
Exception dispatchException = null;try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);// Determine handler for the current request.
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}// Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (logger.isDebugEnabled()) {
logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());if (asyncManager.isConcurrentHandlingStarted()) {
return;
}applyDefaultViewName(request, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Error err) {
triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}/**
* Determine an error ModelAndView via the registered HandlerExceptionResolvers.
* @param request current HTTP request
* @param response current HTTP response
* @param handler the executed handler, or {@code null} if none chosen at the time of the exception
* (for example, if multipart resolution failed)
* @param ex the exception that got thrown during handler execution
* @return a corresponding ModelAndView to forward to
* @throws Exception if no error ModelAndView found
*/
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response,
Object handler, Exception ex) throws Exception {// Check registered HandlerExceptionResolvers...
ModelAndView exMv = null;
for (HandlerExceptionResolver handlerExceptionResolver : this.handlerExceptionResolvers) {
exMv = handlerExceptionResolver.resolveException(request, response, handler, ex);
if (exMv != null) {
break;
}
}
if (exMv != null) {
if (exMv.isEmpty()) {
request.setAttribute(EXCEPTION_ATTRIBUTE, ex);
return null;
}
// We might still need view name translation for a plain error model...
if (!exMv.hasView()) {
exMv.setViewName(getDefaultViewName(request));
}
if (logger.isDebugEnabled()) {
logger.debug("Handler execution resulted in exception - forwarding to resolved error view: " + exMv, ex);
}
WebUtils.exposeErrorRequestAttributes(request, ex, getServletName());
return exMv;
}throw ex;
}

何时该使用何种ExceptionResolver？

Spring提供了很多选择和非常灵活的使用方式，下面是一些使用建议：

1. 如果自定义异常类，考虑加上ResponseStatus注解；
2. 对于没有ResponseStatus注解的异常，可以通过使用ExceptionHandler+ControllerAdvice注解，或者通过配置SimpleMappingExceptionResolver，来为整个Web应用提供统一的异常处理。
3. 如果应用中有些异常处理方式，只针对特定的Controller使用，那么在这个Controller中使用ExceptionHandler注解。
4. 不要使用过多的异常处理方式，不然的话，维护起来会很苦恼，因为异常的处理分散在很多不同的地方。

http://www.cnblogs.com/xinzhao/p/4902295.html