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Spring MVC处理异常有3种方式: (1)使用@ExceptionHandler注解实现异常处理; (2)使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver; (3)实现Spring的异常处理接口HandlerExceptionResolver 自定义自己的异常处理器;
BusinessException和SystemException为自定义异常类,代码如下:
package com.twosnail.exception;import javax.servlet.http.HttpServletRequest;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.ExceptionHandler;@Controllerpublic class BasicExController { /** * 基于@ExceptionHandler异常处理基类 * @return */ @ExceptionHandler public String exception( HttpServletRequest request , Exception ex ) { // 根据不同错误转向不同页面 if( ex instanceof BusinessException ) { return "business-error"; }else if( ex instanceof SystemException ) { return "system-error"; } else { return "error"; } }}
public class DemoController extends BasicExController {}
然而,Dao层、Service层、Controller层抛出的异常(BusinessException、SystemException和其它异常)都能准确显示定义的异常处理页面,达到了统一异常处理的目标。
总结:使用@ExceptionHandler注解实现异常处理,具有集成简单、有扩展性好(只需要将要异常处理的Controller类继承于BasicExController即可)、不需要附加Spring配置等优点,但该方法对已有代码存在入侵性(需要修改已有代码,使继承于BasicExController),在异常处理时不能获取除异常以外的数据。
SimpleMappingExceptionResolver有两种配置方式,可以按自己需求而定,配置代码如下:
在这里,可以设置跳转相应页面。
business-error system-error 500 404
然后在Spring的配置。代码如下:
error/500 error/errorpage error/500
java类代码如下,在这里可以处理相应逻辑,如下,分别处理了jsp页面和json数据:
package com.twosnail.exception;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.ModelAndView;import org.springframework.web.servlet.handler.SimpleMappingExceptionResolver;public class MyselfSimpleMappingExceptionResolver extends SimpleMappingExceptionResolver { @Override protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) { // Expose ModelAndView for chosen error view. String viewName = determineViewName(ex, request); if (viewName != null) {// JSP格式返回 if (!(request.getHeader("accept").indexOf("application/json") > -1 || (request .getHeader("X-Requested-With") != null && request .getHeader("X-Requested-With").indexOf("XMLHttpRequest") > -1))) { // 如果不是异步请求 // Apply HTTP status code for error views, if specified. // Only apply it if we're processing a top-level request. Integer statusCode = determineStatusCode(request, viewName); if (statusCode != null) { applyStatusCodeIfPossible(request, response, statusCode); } return getModelAndView(viewName, ex, request); } else {// JSON格式返回 try { PrintWriter writer = response.getWriter(); writer.write(ex.getMessage()); writer.flush(); } catch (IOException e) { e.printStackTrace(); } return null; } } else { return null; } }}
总结:使用SimpleMappingExceptionResolver进行异常处理,具有集成简单、有良好的扩展性、对已有代码没有入侵性等优点,但方法1仅能获取到异常信息,若在出现异常时,对需要获取除异常以外的数据的情况不适用。
在这里,单独打印出了异常路径,便于在日志中查看,在对SystemException异常进行了特殊处理:
package com.twosnail.exception;import java.util.Map;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerExceptionResolver;import org.springframework.web.servlet.ModelAndView;import org.springframework.web.servlet.View;import org.springframework.web.servlet.view.RedirectView;public class MyExceptionHandler implements HandlerExceptionResolver { public ModelAndView resolveException( HttpServletRequest request, HttpServletResponse response, Object handler, Exception exception ) { System.out.println( "【抛出异常】--异常路径为:" + request.getServletPath() + "\n【异常信息】--" + exception.getMessage() ) ; //如果不是抛出的action业务异常则不处理 if( !( exception instanceof SystemException ) ) { return null; } final SystemException actionE = (SystemException) exception; ModelAndView model = null; if( actionE.getForwardType() == SystemException.FORWARD ) { //进入页面渲染 model = new ModelAndView( actionE.getModelPath(), actionE.getAttributes()); } else if( actionE.getForwardType() == SystemException.REDIRECT ) { model = new ModelAndView( new RedirectView( actionE.getModelPath(), true)); } else { //直接返回页面内容 model = new ModelAndView( new View() { @Override public void render(Maparg0, HttpServletRequest arg1, HttpServletResponse arg2) throws Exception { arg2.setContentType( "text/html" ); arg2.setCharacterEncoding( actionE.getEncode() ); if( actionE.getResponseBody() != null ) { arg2.getWriter().print( actionE.getResponseBody() ); } } @Override public String getContentType() { return "text/html; charset=utf-8"; } } ); } return model; }}
总结:从上面的集成过程可知,使用实现HandlerExceptionResolver接口的异常处理器进行异常处理,具有集成简单、有良好的扩展性、对已有代码没有入侵性等优点。在异常处理时能获取导致出现异常的对象,有利于提供更详细的异常处理信息。而SimpleMappingExceptionResolver就是HandlerExceptionResolver的默认实现类。
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