springMVC异常&&重定向&&转发

2022-08-23 10:28:00

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

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";

    }

}

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

<%@ 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>

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;

@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)

<%@ 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>

MyController.java(定义处理器)

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";

    }

}

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

        ">

     <!-- 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>

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

<?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>

error包中是指定错误页面

nameerrors.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%>">

    <title>错误页面</title>

  </head>

  <body>

       <h1>用户名错误</h1>

       ${ex.message }

  </body>

</html>

ageerrors.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%>">

    <title>错误页面</title>

  </head>

  <body>

       <h1>年龄错误</h1>

       ${ex.message }

  </body>

</html>

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;

@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;

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;

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;

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

        ">

   <!-- 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>

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;

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

        ">

     <!-- 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>

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*异常或者与之指定的异常

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;

    }

}