SpringMVC归纳-2(Session会话、拦截器)

时间：2022-01-16 13:04:59

　　要点：

　　1.HttpSession：一个session的建立是从一个用户向服务器发第一个请求开始，而以用户显式结束或session超时为结束，借助session能在一定时间内记录用户状态。

　　2.ModelAndView：既可以设置URL地址，又可以渲染视图。

　　3.HandlerInterceptor：拦截器接口，通过实现改接口的三个方法（preHandle、postHandle、afterCompletion）可以自定义一个拦截器。

　　实例：

　　实现登录、购物车功能。

　　login.html

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>乐淘登录</title>

</head>

<body>

    <form action="http://localhost:8888/login-commit" method="post">

        <input type="submit" value="login">

    </form>

</body>

</html>

　　mall.html

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>乐淘商场</title>

</head>

<body>

    <form action="http://localhost:8888/shopcar" method="POST">

        <label>请选择要购买的书籍：<br>

            <input type="checkbox" name="bookname" value="C Prime Plus">C Prime Plus<br>

            <input type="checkbox" name="bookname" value="C Prime Plus2">C Prime Plus2<br>

            <input type="checkbox" name="bookname" value="C Prime Plus3">C Prime Plus3<br>

            <input type="checkbox" name="bookname" value="C Prime Plus4">C Prime Plus4<br>

        </label>

        <input type="submit" value="加入购物车">

    </form>

    <form action="http://localhost:8888/quit" method="POST">

        <input value="log out" type="submit">

    </form>

</body>

</html>

　　myshoppingcar.html

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>乐淘购物车</title>

</head>

<body>

    <h2>我的购物车：</h2>

    <!--存在购买时显示已购书籍-->

    <ul th:if="${books.size()} != 0">

        <li th:each="bookcount:${books}" th:text="${bookcount}"></li>

    </ul>

    <!--无购买-->

    <div th:if="${books.size()} == 0">

        您未购买任何书籍！

    </div>

    <form action="http://localhost:8888/mall" method="GET">

        <input type="submit" value="继续购买">

    </form>

</body>

</html>

　　Books.java

package com.example.demo.controller.login;

import java.util.HashMap;

import java.util.Map.Entry;

import java.util.Set;

public class Books {

    private HashMap<String,Integer> books = new HashMap<String,Integer>(); 

    //根据请求URL中获得的表单数组，更新已有书本

    public void refreshBooks(String[] newbooks) {

        for (String book:newbooks) {

            if (books.containsKey(book)) {

                books.put(book, books.get(book)+1);

            }else {

                books.put(book, 1);

            }

        }

    }

    //获取books集合，送往页面

    public Set<Entry<String, Integer>> getbooks(){

        return books.entrySet();

    }

}

　　LoginController.java

package com.example.demo.controller.login;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;

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

import org.springframework.web.bind.annotation.PostMapping;

@Controller

public class LoginController {

    //登录界面

    @GetMapping("login")

    public String getLogin(HttpServletRequest req) {

        HttpSession session = req.getSession();

        //已登录直接进入到商场

        if (session.getAttribute("login")!=null) {

            return "redirect:mall";

        }

        return "login";

    }

    //登录请求处理

    @PostMapping("login-commit")

    public String postLogin(HttpServletRequest req) {

        HttpSession session = req.getSession();

        //session标记登录状态

        session.setAttribute("login",true);

        return "redirect:mall";

    }

    //退出登录，保留购物记录

    @PostMapping("quit")

    public String quit(HttpServletRequest req) {

        HttpSession session = req.getSession();

        session.removeAttribute("login");

        return "redirect:login";

    }

}

　　ShoppingController.java

package com.example.demo.controller.login;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;

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

import org.springframework.web.bind.annotation.PostMapping;

import org.springframework.web.servlet.ModelAndView;

@Controller

public class ShoppingController {

    //商场

    @GetMapping("mall")

    public String getMall() {

        return "mall";

    }

    //我的购物车

    @PostMapping("shopcar")

    public ModelAndView getShopCar(ModelAndView view,HttpServletRequest req) {

        HttpSession session = req.getSession();

        Books books = (Books) session.getAttribute("shopcar");//session会话获取已购书籍

        String[] newbooks = req.getParameterValues("bookname");//新的购物请求

        //从未购买

        if (books==null){

            books = new Books();

        }

        //刷新session会话

        if (newbooks!=null) {

            books.refreshBooks(newbooks);

            session.setAttribute("shopcar", books);

        }

        //刷新model，渲染视图

        view.addObject("books",books.getbooks());

        view.setViewName("myshoppingcar");

        return view;

    }

}

　　LoginInterceptor.java

package com.example.demo.controller.login;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import org.springframework.web.servlet.HandlerInterceptor;

import org.springframework.web.servlet.ModelAndView;

//登录拦截器

public class LoginInterceptor implements HandlerInterceptor {

    @Override

    //在Controller方法之前调用

    public boolean preHandle(HttpServletRequest req,HttpServletResponse res,Object handler) throws IOException {

        HttpSession session = req.getSession();

        if (session.getAttribute("login") != null) {

            System.out.println("login!");

            return true;

        }

        res.sendRedirect("login");

        return false;

    }

    @Override

    public void postHandle(HttpServletRequest req,HttpServletResponse res,Object handler,ModelAndView modelandview) throws Exception {

        //Controller方法处理完，但html页面并未送出显示时调用

    }

    @Override

    public void afterCompletion(HttpServletRequest req,HttpServletResponse res,Object handler,Exception ex) {

        //页面渲染完毕后调用，通常用来回收资源，类似于finally

    }

}

　　SpringWebConfig.java

package com.example.demo.controller.login;

import org.springframework.boot.SpringBootConfiguration;

import org.springframework.web.servlet.config.annotation.InterceptorRegistry;

import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@SpringBootConfiguration

public class SpringWebConfig  implements WebMvcConfigurer{

    //增加拦截器，可以对特定URL设定拦截以检查是否登录

    public void addInterceptors(InterceptorRegistry registry) {

        //装载一个拦截器,可以使用通配符，或字符串数组

        registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/mall","/quit");

    }

}

　　

　　

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