Spring MVC重定向和转发及异常处理

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SpringMVC核心技术---转发和重定向

当处理器对请求处理完毕后，向其他资源进行跳转时，有两种跳转方式：请求转发与重定向。而根据要跳转的资源类型，又可分为两类：跳转到页面与跳转到其他处理器。
对于请求转发的页面，也可以是WEB-INF中页面；对于重定向的页面，不能为WEB-INF中的页面。因为重定向相当于用户再次发出一次请求，而用户是不能直接访问WEB-INF中资源的

1）重定向到页面

FirstController.java

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<style type="text/css">
form{
margin:0px auto;
/* border:1px solid red; */
width:500px; }
</style>
<title></title>
</head> <body>
<form action="${pageContext.request.contextPath }/first.do" method="post">
姓名:<input name="uname"/><br/><br/>
年龄:<input name="uage"/><br/><br/>
<input type="submit" value="注册"/>
</form>
</body>
</html>

welcome.jsp

2）重定向到控制器:

FirstController.java

package cn.controller;import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;/**
*
* @author
*
*/
@Controller
public class FirstController {
//处理器方法 doFirst==========》doSecond
@RequestMapping(value="/first.do")
public String doAddOrder(Model model,String uname,int uage){
model.addAttribute("uname", uname);
model.addAttribute("uage",uage); return "redirect:second.do";
} @RequestMapping(value="/second.do")
public String doList(Model model,String uname,int uage){
model.addAttribute("uname", uname);
model.addAttribute("uage",uage);
System.out.println(uname+"==================");
return "redirect:/welcome.jsp";
}}

其它与上述相同

转发与重定向一样，就不多做解释

异常处理

描述

在J2EE项目的开发中，不管是对底层的数据库操作过程，还是业务层的处理过程，还是控制层的处理过程，都不可避免会遇到各种可预知的、不可预知的异常需要处理。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。
那么，能不能将所有类型的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？答案是肯定的。下面将介绍使用Spring MVC统一处理异常的解决和实现过程。

分析

Spring MVC处理异常常见有4种方式：
1）使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver
2）实现Spring的异常处理SimpleMappingExceptionResolver自定义自己的异常处理器

3）实现HandlerExceptionResolver 接口自定义异常处理器
4）使用注解@ExceptionHandler实现异常处理

我们先介绍三种：

案例

系统异常处理SimpleMappingExceptionResolver

web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
<display-name></display-name>
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

index.jsp页面

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<style type="text/css">
form{
margin:0px auto;
background-color:pink;
width:500px;
}
</style>
<title></title>
</head> <body>
<h1>系统异常处理</h1>
<form action="${pageContext.request.contextPath }/first.do" method="post">
姓名:<input name="name"/><br/><br/>
年龄:<input name="age"/><br/><br/>
<input type="submit" value="注册"/>
</form>
</body>
</html>

errors.jsp(报错是跳转到此页面)

MyController.java(定义处理器)

package cn.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
/**
*
* @author
*
*/
@Controller
public class MyController {
//处理器方法
@RequestMapping(value="/first.do")
public String doFirst(){
//构造异常
int result=5/0;
return "/WEB-INF/index.jsp";
}}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
"> 
<context:component-scan base-package="cn.controller"></context:component-scan> 
<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<property name="defaultErrorView" value="errors.jsp"></property>
<property name="exceptionAttribute" value="ex"></property> </bean></beans>

效果：

实现Spring的异常处理接口SimpleMappingExceptionResolver自定义自己的异常处理器

web.xml

error包中是指定错误页面

nameerrors.jsp

ageerrors.jsp

FirstController.java

package cn.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import cn.exceptions.AgeException;
import cn.exceptions.NameException;
import cn.exceptions.UserInfoException;/**
*
* @author
*
*/
@Controller
public class FirstController {
//处理器方法
@RequestMapping(value="/first.do")
public String doFirst(String name,int age) throws UserInfoException{ if (!"hh".equals(name)) {
throw new NameException("用户名错误");
} if (age>40) {
throw new AgeException("年龄太大");
} return "index.jsp";
}
}

exception包下，指定异常类

UserInfoException.java

package cn.exceptions;
/**
*
* @author
*
*/
public class UserInfoException extends Exception{ public UserInfoException() {
super();
// TODO Auto-generated constructor stub
} public UserInfoException(String message) {
super(message);
// TODO Auto-generated constructor stub
}}

NameException.java

package cn.exceptions;
/**
*
* @author
*
*/
public class NameException extends UserInfoException{ public NameException() {
super();
// TODO Auto-generated constructor stub
} public NameException(String message) {
super(message);
// TODO Auto-generated constructor stub
}}

AgeException.java

package cn.exceptions;/**
*
* @author
*
*/
public class AgeException extends UserInfoException{ public AgeException() {
super();
// TODO Auto-generated constructor stub
} public AgeException(String message) {
super(message);
// TODO Auto-generated constructor stub
}}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
"> 
<context:component-scan base-package="cn.controller"></context:component-scan>

<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<property name="defaultErrorView" value="errors.jsp"></property>
<property name="exceptionAttribute" value="ex"></property> <property name="exceptionMappings">
<props>
<prop key="cn.exceptions.NameException">error/nameerrors.jsp</prop>
<prop key="cn.exceptions.AgeException">error/ageerrors.jsp</prop>
</props>
</property>
</bean></beans>

效果：

实现HandlerExceptionResolver 接口自定义异常处理器

使用Springmvc定义好的SimpleMappingExceptionResolver异常处理器，可以实现发生指定异常后的跳转。但是若要实现在捕获到指定异常时，执行一些操作的目的，它是完成不了的。此时，就需要自定义异常处理器。自定义异常处理器，需要实现HandlerExceptionResolver接口，并且该类需要在Springmvc配置文件中进行注册

定义自己的异常处理类

package cn.resolvers;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;import cn.exceptions.AgeException;
import cn.exceptions.NameException;/**
*
* @author
*
*/
public class MyHandlerExceptionResolver implements HandlerExceptionResolver{ public ModelAndView resolveException(HttpServletRequest request,
HttpServletResponse response, Object handler, Exception ex) { ModelAndView mv=new ModelAndView();
mv.addObject("ex",ex); mv.setViewName("/errors.jsp"); //view
if(ex instanceof NameException){
mv.setViewName("/error/nameerrors.jsp");
} if(ex instanceof AgeException){
mv.setViewName("/error/ageerrors.jsp");
} return mv;
}}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
"> 
<context:component-scan base-package="cn.controller"></context:component-scan>

<bean class="cn.resolvers.MyHandlerExceptionResolver"/></beans>