JAVA高级面试进阶训练营视频教程

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@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：

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

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