【Spring】SpringMVC之拦截器

Spring的HandlerMapping处理器支持拦截器应用。当需要为某些请求提供特殊功能时，例如实现对用户进行身份认证、登录检查等功能。

拦截器必须实现HandlerInterceptor接口，实现了这个接口就会重写三个方法preHandle()、postHandle()和afterCompletion()方法，关于这个三个方法的执行流程都在下面这张图片中：

使用步骤:

1.  编写一个类 实现HandlerInterceptor接口

2.  配置applicationContext.xml

配置文件案例:

    <mvc:interceptors>
        <mvc:interceptor>
            <!--    要拦截的地址 -->
            <mvc:mapping path="/**"/>
            <!-- 匹配拦截地址 中的不拦截的地址  
            <mvc:exclude-mapping path=""/>-->
            <!-- 使用的拦截器类 -->
            <bean class="cn.xdl.filter.MyFilter"></bean>
        </mvc:interceptor>
    </mvc:interceptors>

Demo

UserController.java文件：

package cn.xdl.controller;

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

@Controller
public class UserController {

    @RequestMapping("/login.do")
    public ModelAndView userLogin(String uname,String upass){
        System.out.println(uname);
        System.out.println(upass);
        
        ModelAndView modelview=new ModelAndView("loginResult");
        
        return modelview;
    }
}

UserFilter.java文件：

package cn.xdl.user.filter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class UserFilter implements HandlerInterceptor {

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object arg2, Exception arg3)
            throws Exception {
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object arg2, ModelAndView arg3)
            throws Exception {
    }

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
        /*
         * return true 表示拦截通过
         * return false 表示拦截不通过
         * 
         * 如果是拦截不通过用户的页面会出现一个大白屏，这个时候应该进行请求重定向，比如：response.sendRedirect("loginError.jsp")
         */
        
        String uname = request.getParameter("uname");
        String upass = request.getParameter("upass");
        //对用户的账号和密码进行简单验证
        if(uname==null||upass==null||uname.length()<6||upass.length()<6){
            //拦截  , 
            response.sendRedirect("loginError.jsp");
            return false;
        }
        return true;
    }

}

dispatcher_serverlet-servlet.xml文件：

<?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:mvc="http://www.springframework.org/schema/mvc"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd
        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-4.3.xsd">
    
    <!--指定扫描包-->
    <context:component-scan base-package="cn"></context:component-scan>
    
    <!--开启扫描-->
    <mvc:annotation-driven/>
    
    <!--配置ModelAndView-->
    <bean id="viewResolve" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.InternalResourceView"></property>
        <property name="prefix" value=""></property>
        <property name="suffix" value=".jsp"></property>
    </bean>
    
    <!--配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
                <!--     要拦截的地址，这里是拦截所有地址 -->
                <mvc:mapping path="/**"/>
                <!-- 
                匹配拦截地址中不用拦截的地址  
                <mvc:exclude-mapping path=""/>
                -->
                <!-- 指定的拦截器类 -->
                <bean class="cn.xdl.user.filter.UserFilter"></bean>
        </mvc:interceptor>
    </mvc:interceptors>
    
</beans>

这里的dispatcher_serverlet-servlet.xml文件必须在WEB-INFO目录下，并且dispatcher_serverlet应该和web.xml中对应的<servlet-name>的值一致，详情可以参见SpringMVC的非注解配置的两种方式

web.xml文件：

<?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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
  <display-name>SpringFilterTest</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>dispatcher_serverlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcher_serverlet</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
  <filter>
    <filter-name>EncodingName</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>utf-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>EncodingName</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>

loginError.jsp文件：

<%@ 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>登录失败</title>
</head>
<body>
登录失败
</body>
</html>

 loginResult.java文件

<%@ 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>结果页面</title>
</head>
<body>
登录成功
</body>
</html>

 login.jsp文件

<%@ 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>用户登录</title>
</head>
<body>
<form action="login.do" method="post">
用户名:<input type="text" name="uname" /><br/><br/>
密码:<input type="password" name="upass" /><br/><br/>
<input type="submit" value="登录" />
</form>
</body>
</html>