1、为什么要用Spring的统一异常处理？
项目中无论是controller层、service层还是dao层都会有异常发生。每个过程都单独处理异常，系统的代码耦合度高，工作量大且不好统一，维护的工作量也很大。所以将异常处理从各处理过程解耦出来，这样既保证了相关处理过程的功能较单一，也实现了异常信息的统一处理和维护
2、Spring统一异常处理的方式有哪些？
2.1 使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver。
2.2 实现Spring的异常处理接口HandlerExceptionResolver 自定义自己的异常处理器。
2.3 使用@ExceptionHandler注解实现异常处理
3、做实验
3.1使用SimpleMappingExceptionResolver
3.1.1 在spring的配置文件applicationContext.xml文件中配置SimpleMappingExceptionResolver
<!-- springmvc提供的简单异常处理器 --> <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <!-- 定义默认的异常处理页面，这里的error表示的是error.jsp页面--> <property name="defaultErrorView" value="error" /> <!-- 定义异常处理页面用来获取异常信息的变量名，也可不定义，默认名为exception--> <property name="exceptionAttribute" value="ex" /> <!-- 定义需要特殊处理的异常，这是重要点 --> <property name="exceptionMappings"> <props> <!-- 这里的exception表示的是exception.jsp页面 --> <prop key="org.hope.lee.exception.UserException">exception</prop> <prop key="org.hope.lee.exception.CustomerException">customerException</prop> </props> <!-- 还可以定义其他的自定义异常 --> </property> </bean>
3.1.2定义自己的异常
package org.hope.lee.exception; public class UserException extends Exception{ private static final long serialVersionUID = 1L; private String errorMsg; public UserException(String errorMsg) { super(); this.errorMsg = errorMsg; } public String getErrorMsg() { return errorMsg; } public void setErrorMsg(String errorMsg) { this.errorMsg = errorMsg; } }
package org.hope.lee.exception; public class CustomerException extends RuntimeException{ private String errorException; public CustomerException(String errorException) { super(); this.errorException = errorException; } public String getErrorException() { return errorException; } public void setErrorException(String errorException) { this.errorException = errorException; } }
3.1.3 写几个简单的页面error.jsp exception.jsp customerException.jsp
error.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> sorry, your request has some errors </body> </html>
exception.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> sorry, your request has ${ex.errorMsg} </body> </htm
customerException.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> sorry, your request has customerException:${ex.errorException} </body> </html>
3.1.4 Controller层
package org.hope.lee.controller; import org.hope.lee.exception.CustomerException; import org.hope.lee.exception.UserException; import org.hope.lee.model.User; import org.hope.lee.service.UserService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.ui.ModelMap; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.servlet.ModelAndView; @Controller @RequestMapping("/user") public class UserController { @Autowired private UserService userService; @RequestMapping("/index") public String index() { return "userDetail"; } @RequestMapping("/detail") public ModelAndView detail(String id) throws UserException { if("0".equals(id)) { throw new UserException("id不能为0"); } if("10".equals(id)) { throw new CustomerException("id不能为10"); } User user = userService.findUserById(Integer.parseInt(id)); ModelAndView mv = new ModelAndView(); mv.addObject("user", user); mv.setViewName("success"); return mv; } }
3.1.4 进行测试
①启动项目
②浏览器输入：http://localhost:8088/springmvc-exception/user/detail?id=1(这个是正常时候)
③浏览器输入：http://localhost:8088/springmvc-exception/user/detail?id=0
④浏览器输入：http://localhost:8088/springmvc-exception/user/detail?id=10
3.2自定义全局异常处理。
3.2.1 定义自己的异常处理类实现HandlerExceptionResolver
package org.hope.lee.exception; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.springframework.web.servlet.HandlerExceptionResolver; import org.springframework.web.servlet.ModelAndView; /** * 定义全局异常处理器 */ public class ExceptionResolver implements HandlerExceptionResolver{ @Override public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) { ModelAndView mav = new ModelAndView(); if(ex instanceof UserException) { UserException ue = (UserException)ex; mav.addObject("ex", ue); mav.setViewName("exception"); } else if(ex instanceof CustomerException) { CustomerException ce = (CustomerException)ex; mav.addObject("ex", ce); mav.setViewName("customerException"); } else { mav.addObject("ex", "未知错误"); mav.setViewName("error"); } return mav; } }
3.2.2 在applicationContext.xml中配置异常处理器
<bean class="org.hope.lee.exception.ExceptionResolver"/>
3.3 使用@ExceptionHandler
3.3.1 定义一个BaseController，所有的Controller层都要继承它
package org.hope.lee.controller; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.hope.lee.exception.CustomerException; import org.hope.lee.exception.UserException; import org.springframework.web.bind.annotation.ExceptionHandler; public class BaseController { @ExceptionHandler public String exp(HttpServletRequest req, HttpServletResponse resp, Exception ex) { req.setAttribute("ex", ex); if(ex instanceof UserException) { return "exception"; } else if(ex instanceof CustomerException) { return "customerException"; } else { return "error"; } } }
3.3.2 定义一个Controller，继承BaseController
package org.hope.lee.controller; import org.hope.lee.service.SellerService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; @Controller public class SellerController extends BaseController{ @Autowired private SellerService sellerService; @RequestMapping("/good/update") public void updateGood(String id) { sellerService.updateGoodsById(Integer.parseInt(id)); } }
3.3.3 测试一下，启动项目在浏览器访问：http://localhost:8088/springmvc-exception/good/update?id=0
https://gitee.com/huayicompany/spring-learn/tree/master/springmvc-exception
参考：
[1] 博客，http://blog.csdn.net/eson_15/article/details/51731567