过滤器（Filter）
依赖于servlet容器。在实现上基于函数回调，可以对几乎所有请求进行过滤，但是缺点是一个过滤器实例只能在容器初始化时调用一次。包括：过滤低俗文字、危险字符等
拦截器（Interceptor）
依赖于web框架，依赖于SpringMVC（或Struts2）框架。在实现上基于Java的反射机制，属于面向切面编程（AOP）的一种运用。同时一个拦截器实例在一个controller生命周期之内可以多次调用。
拦截器与过滤器的区别
1、拦截器是基于java的反射机制的，而过滤器是基本函数回调。
2、拦截器不依赖于servlet容器，过滤器依赖于servlet容器。
3、拦截器只能对action请求起作用，过滤器可以对几乎所有的请求起作用。
4、拦截器可以访问action上下文、值栈里的对象，而过滤器不能访问。
5、在action的生命周期中，拦截器可以被多次调用，而过滤器只能在容器初始化时被调用过一次。
拦截器例子
整体架构
项目架构
1、pom.xml
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.0.8.RELEASE</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.8</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.40</version>
</dependency>
</dependencies>
2、web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<display-name>Archetype Created Web Application</display-name>
<!--1.注册DispatcherServlet-->
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--关联一个springmvc的配置文件:【servlet-name】-servlet.xml-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc.xml</param-value>
</init-param>
<!--启动级别-1-->
<load-on-startup>1</load-on-startup>
</servlet>
<!--/ 匹配所有的请求；（不包括.jsp）-->
<!--/* 匹配所有的请求；（包括.jsp）如果这里写/* 跳转jsp页面时就是在走一次DispatcherServlet，
就会出现 success.jsp.jsp页面的错误情况-->
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<!--处理post乱码-->
<filter>
<filter-name>encoding</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>encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
3、springmvc.xml配置文件
<?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:p="http://www.springframework.org/schema/p"
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
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<context:component-scan base-package="com"></context:component-scan>
<!--处理json乱码-->
<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>
<mvc:default-servlet-handler></mvc:default-servlet-handler>
<bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/"></property>
<property name="suffix" value=".jsp"></property>
</bean>
<!--关于拦截器的配置-->
<mvc:interceptors>
<mvc:interceptor>
<!--/** 包括路径及其子路径-->
<!--/admin/* 拦截的是/admin/add等等这种 , /admin/add/user不会被拦截-->
<!--/admin/** 拦截的是/admin/下的所有-->
<mvc:mapping path="/**"/>
<!--bean配置的就是拦截器-->
<bean class="com.fan.interceptor.loginInterceptor"/>
</mvc:interceptor>
</mvc:interceptors>
</beans>
4、index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<h2>Hello World!</h2>
<p><a href="${pageContext.request.contextPath}/tologin">登录页面</a></p>
<p><a href="${pageContext.request.contextPath}/index">主页</a></p>
</body>
</html>
5、login.jsp
<%--
Created by IntelliJ IDEA.
User: Mr Wei
Date: 2021/1/12
Time: 21:34
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/login" method="post">
用户名：<input type="text" name="username"><br/>
密码：<input type="text" name="password"><br/>
<input type="submit">
</form>
</body>
</html>
6、loginsuccess.jsp
<%--
Created by IntelliJ IDEA.
User: Mr Wei
Date: 2021/1/12
Time: 21:31
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>主页</h1>
<h3>登录成功</h3>
${username}
<p><a href="${pageContext.request.contextPath}/loginout">注销</a></p>
</body>
</html>
7、拦截器
package com.fan.interceptor;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpSession;
public class loginInterceptor implements HandlerInterceptor {
//如果返回true执行下一个拦截器
//如果返回false就不执行下一个拦截器
public boolean preHandle(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, Object handler) throws Exception {
System.out.println("------------处理前------------");
// 如果是登陆页面则放行
System.out.println("uri: " + request.getRequestURI());//得到请求路径
if (request.getRequestURI().contains("login")) {//包含login的就放行
return true;
}
HttpSession session = request.getSession();
// 如果用户已登陆也放行
if(session.getAttribute("username") != null) {
return true;
}
// 用户没有登陆跳转到登陆页面
request.getRequestDispatcher("/login.jsp").forward(request, response);
return false;
}
public void postHandle(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
}
public void afterCompletion(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, Object handler, Exception ex) throws Exception {
}
}
8、controller类
package com.fan.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpSession;
@Controller
public class ControllerTest {
@RequestMapping("/tologin")
public String Tologin(){
return "login";
}
@RequestMapping("/index")
public String Tologinsuccess(){
return "loginsuccess";
}
@RequestMapping("/login")
public String login(String username, String password, HttpSession session){
System.out.println(username+" "+password);
session.setAttribute("username",username);
return "loginsuccess";
}
@RequestMapping("/loginout")
public String loginout(HttpSession session){
session.removeAttribute("username");
return "index";
}
}
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