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  • springMVC异常&&重定向&&转发

    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

    复制代码
    package cn.controller;


import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;



@Controller
public class FirstController {
    @RequestMapping(value="/first.do")
    public String doAddOrder(Model model,String uname,int uage){
        model.addAttribute("uname", uname);
        model.addAttribute("uage",uage);
        
        return "redirect:/welcome.jsp";
    }

    
    
}
    复制代码

    index.jsp

    复制代码
    <%@ 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; */
         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>
    复制代码

    welcome.jsp

    复制代码
    <%@ 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%>">
    
    <title>欢迎页面</title>
  
  </head>
  <h1>欢迎访问${uname }${param.uage }</h1>

  </body>
</html>
    复制代码

    2）重定向到控制器:

    FirstController.java

    复制代码
    package cn.controller;


import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;



@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";
    }
    
    
    
}
    复制代码

    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

    复制代码
    <?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>
    复制代码

    index.jsp页面

    复制代码
    <%@ 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;
         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>
    复制代码

    errors.jsp(报错是跳转到此页面)

    复制代码
    <%@ 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%>">
   
    <title>错误页面</title>
  </head>
  
  <body>
       <h1>我是所有错误消息显示页面</h1>
       ${ex.message }
  </body>
</html>
    复制代码

    MyController.java(定义处理器)

    复制代码
    package cn.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@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";
    }


    
}
    复制代码

    applicationContext.xml

    复制代码
    <?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
        ">
        
     <!-- 包扫描器 -->
     <context:component-scan base-package="cn.controller"></context:component-scan>
    
    <!-- 注册系统异常处理器 -->
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <property name="defaultErrorView" value="errors.jsp"></property>
        <property name="exceptionAttribute" value="ex"></property>
   
    </bean>
    
  
</beans>
    复制代码

    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

    复制代码
    <?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>
    复制代码

    error包中是指定错误页面

    nameerrors.jsp

    复制代码
    <%@ 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%>">
   
    <title>错误页面</title>
  </head>
  
  <body>
       <h1>用户名错误</h1>
       ${ex.message }
  </body>
</html>
    复制代码

    ageerrors.jsp

    复制代码
    <%@ 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%>">
   
    <title>错误页面</title>
  </head>
  
  <body>
       <h1>年龄错误</h1>
       ${ex.message }
  </body>
</html>
    复制代码

    FirstController.java

    复制代码
    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;



@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";
    }
}
    复制代码

    exception包下，指定异常类

    UserInfoException.java

    复制代码
    package cn.exceptions;

public class UserInfoException extends Exception{

    public UserInfoException() {
        super();
        // TODO Auto-generated constructor stub
    }

    public UserInfoException(String message) {
        super(message);
        // TODO Auto-generated constructor stub
    }

}
    复制代码

     NameException.java

    复制代码
    package cn.exceptions;

public class NameException extends UserInfoException{

    public NameException() {
        super();
        // TODO Auto-generated constructor stub
    }

    public NameException(String message) {
        super(message);
        // TODO Auto-generated constructor stub
    }

    

}
    复制代码

     AgeException.java

    复制代码
    package cn.exceptions;


public class AgeException extends UserInfoException{

    public AgeException() {
        super();
        // TODO Auto-generated constructor stub
    }

    public AgeException(String message) {
        super(message);
        // TODO Auto-generated constructor stub
    }

}
    复制代码

    applicationContext.xml

    复制代码
    <?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
        ">
     
   <!-- 配置包扫描器-->
   <context:component-scan base-package="cn.controller"></context:component-scan>
   <!-- 注册系统异常处理器 --> 
   <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>
    复制代码

    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

    复制代码
    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;


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;
    }

}
    复制代码

    applicationContext.xml

    复制代码
    <?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
        ">
        
     <!-- 包扫描器 -->
     <context:component-scan base-package="cn.controller"></context:component-scan>
    <!-- 注册自定义异常处理器 -->
     <bean class="cn.resolvers.MyHandlerExceptionResolver"/>
  
</beans>
    复制代码

    其它与上述的一样

    异常处理注解@ExceptionHandler

     1）异常处理注解@ExceptionHandler第一版

     

     其它配置都一样

    @ExceptionHandler()可以不写或者顶级异常或者与之指定的异常

    复制代码
    package cn.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

import cn.exceptions.AgeException;
import cn.exceptions.NameException;
import cn.exceptions.UserInfoException;

@Controller
public class MyController extends BaseController{
   //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 "/WEB-INF/jsp/index.jsp";
    }
    
    @ExceptionHandler
    public ModelAndView handlerException(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;
    }
}
    复制代码

    applicationContext.xml===(只需写一个包扫描器就行)

    index.jsp

    error.jsp(错误页面)

    效果：
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  • 原文地址：https://www.cnblogs.com/hr1997/p/6253472.html
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