Java笔记之SpringMVC(六):拦截器

0.说在前面

　　基于SpringMVC文件上传项目

1.新建包com.springmvc.demo.interceptor,并新建RequestInterceptor类,实现HandlerInterceptor接口

package com.springmvc.demo.interceptor;

import java.util.Date;

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

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

public class RequestInterceptor implements HandlerInterceptor{
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        System.out.println("preHandle在Controller之前被调用......");
        return HandlerInterceptor.super.preHandle(request, response, handler);
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle在Controller被调用返回ModelAndView之后被调用......");
        //在返回的ModelAndView对象中新加一个数据对象
        modelAndView.addObject("currentDate", new Date());
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println("afterCompletion在视图被访问之后被调用......");
    }
}

2.修改springmvc.xml文件,添加拦截器的配置

<?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/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        https://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">
        
    <!-- 开启注解扫描, base-package配置Controller所在的基础包-->
    <context:component-scan base-package="com.springmvc.demo.controller"></context:component-scan>
    
    <!-- 配置视图解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>
    
    <!-- 配置文件上传解析器,设置最大文件大小为10M(10*1024*1024) -->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="maxUploadSize" value="10485760"></property>
    </bean>
    
    <!-- 配置拦截器,其中可以配置多个拦截器 -->
    <mvc:interceptors>
        <!-- 在其中完成一个拦截器的配置 -->
        <mvc:interceptor>
            <!--拦截器拦截的请求,这里配置的是所有SpringMVC的请求  -->
            <mvc:mapping path="/*.action"/>
            <!-- 拦截器放行的请求,对该请求不进行拦截 -->
            <mvc:exclude-mapping path="/login.action"/>
            <!-- 配置使用的拦截器类 -->
            <bean class="com.springmvc.demo.interceptor.RequestInterceptor"></bean>
        </mvc:interceptor>
    </mvc:interceptors>
    
</beans>

3.新建LoginController类

package com.springmvc.demo.controller;

import javax.servlet.http.HttpServletRequest;

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

@Controller
public class LoginController {
    @RequestMapping("/login.action")
    public String doLogin(HttpServletRequest request){
        System.out.println("LoginController的doLogin方法被访问了......");
        request.setAttribute("message", "登陆成功");
        return "success";
    }
    
    @RequestMapping("/login2.action")
    public String doLogin2(HttpServletRequest request){
        System.out.println("LoginController的doLogin2方法被访问了......");
        request.setAttribute("message", "登陆成功");
        return "success";
    }
}

4.修改success.jsp页面,添加获取ModelAndView中currentDate的值和控制台打印的Java代码

<%@ 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>成功页面</title>
</head>
<body>
${message }---${currentDate }
<%
    System.out.println("视图已经被访问了......");
%>
</body>
</html>

5.启动项目,首先访问http://localhost:8080/springmvc_demo/login.action

从页面信息和后台信息打印可以看出,访问/login.action并没有被拦截器拦截,拦截器中的一系列打印信息和设置的currentDate都没有执行.

6.访问http://localhost:8080/springmvc_demo/login2.action

从页面信息和后台信息可以看出/login2.action被拦截器拦截了,其中的操作也都执行了,设置的日期信息在页面也正常可以获取到.拦截器中的三个方法的执行顺序也在打印信息中得到印证.