阅读完需:约 6 分钟
SpringMVC 中的拦截器,相当于 Jsp/Servlet 中的过滤器,只不过拦截器的功能更为强大。
拦截器的定义非常容易:
@Component
public class MyInterceptor1 implements HandlerInterceptor {
/**
* 这个是请求预处理的方法,只有当这个方法返回值为 true 的时候,后面的方法才会执行
* @param request
* @param response
* @param handler
* @return
* @throws Exception
*/
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("MyInterceptor1:preHandle");
return true;
}
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("MyInterceptor1:postHandle");
}
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("MyInterceptor1:afterCompletion");
}
}
@Component
public class MyInterceptor2 implements HandlerInterceptor {
/**
* 这个是请求预处理的方法,只有当这个方法返回值为 true 的时候,后面的方法才会执行
* @param request
* @param response
* @param handler
* @return
* @throws Exception
*/
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("MyInterceptor2:preHandle");
return true;
}
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("MyInterceptor2:postHandle");
}
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("MyInterceptor2:afterCompletion");
}
}
拦截器定义好之后,需要在 SpringMVC 的配置文件中进行配置:
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/**"/>
<ref bean="myInterceptor1"/>
</mvc:interceptor>
<mvc:interceptor>
<mvc:mapping path="/**"/>
<ref bean="myInterceptor2"/>
</mvc:interceptor>
</mvc:interceptors>
如果存在多个拦截器,拦截规则如下:
- preHandle 按拦截器定义顺序调用
- postHandler 按拦截器定义逆序调用
- afterCompletion 按拦截器定义逆序调用
- postHandler 在拦截器链内所有拦截器返成功调用
- afterCompletion 只有 preHandle 返回 true 才调用
验证用户是否登录 (认证用户)
实现思路
1、有一个登陆页面,需要写一个controller访问页面。
2、登陆页面有一提交表单的动作。需要在controller中处理。判断用户名密码是否正确。如果正确,向session中写入用户信息。返回登陆成功。
3、拦截用户请求,判断用户是否登陆。如果用户已经登陆。放行, 如果用户未登陆,跳转到登陆页面
测试:
1、编写一个登陆页面 login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<h1>登录页面</h1>
<hr>
<body>
<form action="${pageContext.request.contextPath}/user/login">
用户名:<input type="text" name="username"> <br>
密码:<input type="password" name="pwd"> <br>
<input type="submit" value="提交">
</form>
</body>
</html>
2、编写一个Controller处理请求
package com.kuang.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpSession;
@Controller
@RequestMapping("/user")
public class UserController {
//跳转到登陆页面
@RequestMapping("/jumplogin")
public String jumpLogin() throws Exception {
return "login";
}
//跳转到成功页面
@RequestMapping("/jumpSuccess")
public String jumpSuccess() throws Exception {
return "success";
}
//登陆提交
@RequestMapping("/login")
public String login(HttpSession session, String username, String pwd) throwsException {
// 向session记录用户身份信息
System.out.println("接收前端==="+username);
session.setAttribute("user", username);
return "success";
}
//退出登陆
@RequestMapping("logout")
public String logout(HttpSession session) throws Exception {
// session 过期
session.invalidate();
return "login";
}
}
3、编写一个登陆成功的页面 success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1>登录成功页面</h1>
<hr>
${user}
<a href="${pageContext.request.contextPath}/user/logout">注销</a>
</body>
</html>
4、在 index 页面上测试跳转!启动Tomcat 测试,未登录也可以进入主页!
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<h1>首页</h1>
<hr>
<%--登录--%>
<a href="${pageContext.request.contextPath}/user/jumplogin">登录</a>
<a href="${pageContext.request.contextPath}/user/jumpSuccess">成功页面</a>
</body>
</html>
5、编写用户登录拦截器
package com.kuang.interceptor;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class LoginInterceptor implements HandlerInterceptor {
public boolean preHandle(HttpServletRequest request, HttpServletResponseresponse, Object handler) throws ServletException, IOException {
// 如果是登陆页面则放行
System.out.println("uri: " + request.getRequestURI());
if (request.getRequestURI().contains("login")) {
return true;
}
HttpSession session = request.getSession();
// 如果用户已登陆也放行
if(session.getAttribute("user") != null) {
return true;
}
// 用户没有登陆跳转到登陆页面
request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request,response);
return false;
}
public void postHandle(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView)throws Exception {
}
public void afterCompletion(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
}
}
6、在Springmvc的配置文件中注册拦截器
<!--关于拦截器的配置-->
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/**"/>
<bean id="loginInterceptor" class="com.kuang.interceptor.LoginInterceptor"/>
</mvc:interceptor>
</mvc:interceptors>
7、再次重启Tomcat测试!
OK,测试登录拦截功能无误.