SpringMVC Java framework (six) interceptor

SpringMVC: Interceptor

SpringMVC processor interceptors like filter Filter Servlet Development, processor for preprocessing and postprocessing. Developers can define some interceptors themselves to perform specific functions.

The difference between the filter and the interceptor:
1. The filter
part of the servlet specification, any java web project can be used
after the configured url-pattern of / *, can intercept all resources to be accessed
2. interceptor
to intercept is a specific application of AOP thought.
Interceptors are SpringMVC framework of their own, only to use the framework of the project in order to use SpringMVC
interceptor will intercept access control method , if the visit is jsp / html / css / image / js will not be intercepted

Custom implementation steps interceptor

How to implement the interceptor that it?

Want a custom interceptor must implement HandlerInterceptor interface.

1. custom interceptor

package com.kuang.interceptor;

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 {

    //在请求处理的方法之前执行
    //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
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("------------处理前------------");
        return true;
    }

    //在请求处理方法执行之后执行
    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("------------处理后------------");
    }

    //在dispatcherServlet处理后执行,做清理工作.
    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("------------清理------------");
    }
}

2. Configure SpringMVC interceptor

<!--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.kuang.interceptor.MyInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

3.index.jsp

<a href="${pageContext.request.contextPath}/interceptor">拦截器测试</a>

4.Controller

package com.kuang.controller;

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

//测试拦截器的控制器
@Controller
public class InterceptorController {

    @RequestMapping("/interceptor")
    @ResponseBody
    public String testFunction() {
        System.out.println("控制器中的方法执行了");
        return "hello";
    }
}

run:

Case Implementation: Verify user login (user authentication)

Realization of ideas

1 there is a landing page, you need to write a controller to access the page.

2 landing page have a motion to submit the form. Need to be addressed in the controller. Determine whether the correct user name and password. If correct, write user information to the session. Back to Login success.

3 intercept user requests, determine whether the user login. If the user is logged in. Release, if the user is not logged in, jump to the landing page

Written Controller

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) throws Exception {
        // 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";
    }
}

Write blocker

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 {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, 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;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

    }
}

Profiles

        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean id="loginInterceptor" class="com.kuang.interceptor.LoginInterceptor"/>
        </mvc:interceptor>

Front End - Home

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<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>

Front End - success page

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${user}
<a href="${pageContext.request.contextPath}/user/logout">注销</a>
</body>
</html>