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.****.net/eson_15/article/details/51731567