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SpringMVC-拦截器

拦截器

拦截器

1. 过滤器与拦截器的区别

拦截器是AOP思想的具体应用。

过滤器

servlet规范中的一部分，任何java web工程都可以使用
在url-pattern中配置了/*之后，可以对所有要访问的资源进行拦截

拦截器

拦截器是SpringMVC框架自己的，只有使用了SpringMVC框架的工程才能使用
拦截器只会拦截访问的控制器方法，如果访问的是jsp/html/css/image/js是不会进行拦截的

2. 自定义拦截器

1. 编写拦截器

拦截器要实现HandlerInterceptor接口

package com.wang.config;

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

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

public class MyInterceptor implements HandlerInterceptor {

    //return true;  执行下一个执行器, 放行
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("===============================处理前==============================");
        return true;
    }

    //日志
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("===============================处理后==============================");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("===============================清理==============================");
    }
}

2. 在Spring中配置拦截器

<?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: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
       https://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <context:component-scan base-package="com.wang.controller"/>

    <mvc:annotation-driven/>
    <mvc:default-servlet-handler/>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          id="internalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

    <!--拦截器配置-->
    <mvc:interceptors>
        <mvc:interceptor>
            <!--包括这个请求下面的所有请求(/**)-->
            <mvc:mapping path="/**"/>
            <bean class="com.wang.config.MyInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>


</beans>

3. 在controller使用拦截器

package com.wang.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

    @GetMapping("/t1")
    public String test() {
        System.out.println("TestController ==> test() 已执行");
        return "OK";
    }
}

3. 利用拦截器做用户登录验证

1. 编写前端

1. 登录页面

<%--
  Created by IntelliJ IDEA.
  User: Wang
  Date: 2020/9/11
  Time: 15:52
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录页面</title>
</head>
<body>

<%--在WEB-INF下的所有页面或者资源, 只能通过controller, 或者servlet进行访问--%>

<h1>登录页面</h1>

<form action="${pageContext.request.contextPath}/user/login" method="post">
    用户名: <input type="text" name="username">
    密码: <input type="text" name="password">
    <input type="submit" value="提交">
</form>

</body>
</html>

2. 首页

<%--
  Created by IntelliJ IDEA.
  User: Wang
  Date: 2020/9/11
  Time: 15:51
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>首页</title>
</head>
<body>

<h1>首页</h1>

<span>${username}</span>

<p>
    <a href="${pageContext.request.contextPath}/user/goOut">注销</a>
</p>

</body>
</html>

3. 启动页

<%--
  Created by IntelliJ IDEA.
  User: Wang
  Date: 2020/9/11
  Time: 15:28
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>默认页面</title>
  </head>
  <body>
  <a href="${pageContext.request.contextPath}/user/goLoginPage">登录页面</a>

  <a href="${pageContext.request.contextPath}/user/goMainPage">首页</a>
  </body>
</html>

2. 编写controller

package com.wang.controller;

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

import javax.servlet.http.HttpSession;

@Controller
@RequestMapping("/user")
public class LoginController {

    //跳转到login
    @RequestMapping("/goLoginPage")
    public String loginPage() {
        return "login";
    }

    @RequestMapping("/login")
    public String login(String username, String password, HttpSession session, Model model) {
        //把用户的信息保存在session中
        session.setAttribute("userLoginInfo", username);

        model.addAttribute("username", username);
        return "main";
    }

    //跳转到main
    @RequestMapping("/goMainPage")
    public String mainPage() {
        return "main";
    }

    //注销
    @RequestMapping("/goOut")
    public String goOut(HttpSession session) {
        //移除节点
        session.removeAttribute("userLoginInfo");
        return "main";
    }
}

3. 编写拦截器

package com.wang.config;

import org.springframework.web.servlet.HandlerInterceptor;

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

public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        HttpSession session = request.getSession();
        //放行 : 判断什么情况下登录
        //session中存在用户信息的时候放行
        if (session.getAttribute("userLoginInfo") != null) {
            return true;
        }
        //在登录页面的时候也放行
        if (request.getRequestURI().contains("goLogin")) {
            return true;
        }

        //第一次登录也是没有session的, 此时也要放行
        //包含login,说明正在登录
        if (request.getRequestURI().contains("login")) {
            return true;
        }


        //判断什么情况下没有登录
        //不在登录页或者没有登录的, 转发到登录页面
        request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
        return false;
    }
}

4. 配置拦截器

<?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: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
       https://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <context:component-scan base-package="com.wang.controller"/>

    <mvc:annotation-driven/>
    <mvc:default-servlet-handler/>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          id="internalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

    <!--拦截器配置-->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/user/**"/>
            <bean class="com.wang.config.LoginInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>


</beans>

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原文地址：https://www.cnblogs.com/wang-sky/p/13653003.html