Spring MVC异常处理详解 ExceptionHandler good

2022-08-09 08:16:51

@ControllerAdvice(basePackageClasses = AcmeController.class)

public class AcmeControllerAdvice extends ResponseEntityExceptionHandler {

    @ExceptionHandler(YourException.class)

    @ResponseBody

    ResponseEntity<?> handleControllerException(HttpServletRequest request, Throwable ex) {

        HttpStatus status = getStatus(request);

        return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status);

    }

    private HttpStatus getStatus(HttpServletRequest request) {

        Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");

        if (statusCode == null) {

            return HttpStatus.INTERNAL_SERVER_ERROR;

        }

        return HttpStatus.valueOf(statusCode);

    }

}

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：

根据异常的类型，将异常映射到视图；
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；
处理异常时，记录log信息；
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。

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。
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。
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。

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。
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：

如果自定义异常类，考虑加上ResponseStatus注解；
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。
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。
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

https://www.cnblogs.com/softidea/p/4949620.html

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