Web体系结构与程序设计实验2

记录实验2过程及代码。

注意Tomcat10 -> jakarta.servlet-api，Tomcat9以下 -> javax.servlet-api。

1 创建 Servlet 项目

java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(value = "/FirstServlet")
public class FirstServlet extends HttpServlet { // 继承HttpServlet
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  // 重写doGet
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 重写doPost
        super.doPost(req, resp);
    }
}

2 处理并展示请求信息

java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(value = "/SecondServlet")
public class SecondServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String parameter1 = req.getParameter("parameter1");  // 获取请求参数
        String header = req.getHeader("parameter2");  // 获取http头信息
        ServletContext context = getServletContext();
        context.log(parameter1); // 输出到log里
        context.log(header);
        PrintWriter out = resp.getWriter();
        out.println(parameter1); // 输出到响应体里
        out.println(header);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

实际效果：

ApiFox需要先设置好前置URL：

（要达到上图这个效果，需要先在运行配置里的log部分显示所有的log，然后在右侧筛选处选择all）

3 请求转发实践

java
// ThirdServlet_1.java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(value = "/ThirdServlet_1")
public class ThirdServlet_1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.getRequestDispatcher("/ThirdServlet_2").forward(req, resp); // 转发
        log("Request Forwarded");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

// ThirdServlet_2.java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(value = "/ThirdServlet_2")
public class ThirdServlet_2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        log(req.getParameter("parameter")); // 收到请求 输出log
        log("Request Received");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

效果：

4 重定向实践

java
// FourthServlet_1.java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(value = "/FourthServlet_1")
public class FourthServlet_1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setStatus(302); // 设置状态码
        resp.setHeader("Location", "/WebStructure/FourthServlet_2"); // 重定向
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

// FourthServlet_2.java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(value = "/FourthServlet_2")
public class FourthServlet_2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        log("Request Received"); // 收到请求 打印log
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

效果：

5 包含实践

java
// FifthServlet_1.java
package org.example.webstructure.experiment2;

import com.google.gson.Gson;
import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(value = "/FifthServlet_1")
public class FifthServlet_1 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        RequestDispatcher requestDispatcher = req.getRequestDispatcher("/FifthServlet_2"); // 设定目标资源路径
        requestDispatcher.include(req, resp); // 包含
        PrintWriter printWriter = resp.getWriter();
        printWriter.write("Wrote from FifthServlet_1\n"); // 写入
    }

    @Override
    protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPut(req, resp);
    }
}

// FifthServlet_2.java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(value = "/FifthServlet_2")
public class FifthServlet_2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter printWriter = resp.getWriter();
        printWriter.write("Wrote from FifthServlet_2\n"); // 写入
    }
}

效果：

6 Cookie实践

java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.time.LocalDateTime;

@WebServlet(value = "/SixthServlet")
public class SixthServlet extends HttpServlet {

    LocalDateTime time = null;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.addCookie(new Cookie("parameter1", "value1"));
        if (this.time == null) {
            this.time = LocalDateTime.now();
        } else {
            resp.addCookie(new Cookie("lastLoginTime", this.time.toString()));
            this.time = LocalDateTime.now();
        }
    }
}

效果：

第一次请求：

第二次请求：

7 Session 实践

java
// SeventhServlet_1.java
package org.example.webstructure.experiment2;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

@WebServlet(value = "/SeventhServlet_1")
public class SeventhServlet_1 extends HttpServlet {

    Map<String, String> userInfo = new HashMap<String, String>(); // 假装这是数据库

    @Override
    public void init() throws ServletException {
        this.userInfo.put("user1", "123456"); // 数据库里有用户user1 密码是123456
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("userName"); // 获取参数
        String password = req.getParameter("userPassword");
        PrintWriter out = resp.getWriter();
        if (Objects.equals(this.userInfo.get(name), password)) { // 登录验证
            HttpSession httpSession = req.getSession();
            httpSession.setAttribute("user", new UserEntity(name, password)); // 用户信息存储到 HttpSession 对象中
            out.write("Login Success!\n");
        } else {
            out.write("UserName or UserPassword is Incorrect!\n");
        }
    }
}

// SeventhServlet_2.java
package org.example.webstructure.experiment2;

import com.google.gson.Gson;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;

import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(value = "/SeventhServlet_2")
public class SeventhServlet_2 extends HttpServlet {

    Gson gson = new Gson(); // 生成Json字符串用的

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        UserEntity user = (UserEntity) req.getSession().getAttribute("user"); // 先尝试获取用户信息
        if (user == null) { // 这就说明还没登录
            resp.getWriter().write("User is not Logged In!");
            return;
        }
        int operation = Integer.parseInt(req.getParameter("operation")); // 获取操作
        PrintWriter out = resp.getWriter();
        switch (operation) {
            case 1: {
                user.addGood(req.getParameter("goodName")); // 增
                break;
            }
            case 2: {
                user.deleteGood(req.getParameter("goodName")); // 删
                break;
            }
            case 3: {
                user.setGoodNumber(req.getParameter("goodName"),  Integer.parseInt(req.getParameter("goodNumber"))); // 改
                break;
            }
            default: {
                out.write("Operation not recognized");
                return;
            }
        }
        out.write(gson.toJson(user.shoppingCart)); // 查
    }
}

// UserEntity.java
package org.example.webstructure.experiment2;

import java.util.ArrayList;
import java.util.Objects;

// 用户数据类
public class UserEntity {
    String userName;
    String password;
    ArrayList<Good> shoppingCart = new ArrayList<>(); // 购物车信息

    public UserEntity(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }

    // 增加商品
    public void addGood(String goodName) {
        for (Good good : this.shoppingCart) {
            if (Objects.equals(good.name, goodName)) {
                good.number += 1;
                return;
            }
        }
        this.shoppingCart.add(new Good(goodName, 1));
    }

    // 删除商品
    public boolean deleteGood(String goodName) {
        for (Good good : this.shoppingCart) {
            if (Objects.equals(good.name, goodName)) {
                this.shoppingCart.remove(good);
                return true;
            }
        }
        return false;
    }

    // 修改商品数量
    public void setGoodNumber(String goodName, int goodNumber) {
        for (Good good : this.shoppingCart) {
            if (Objects.equals(good.name, goodName)) {
                good.number = goodNumber;
                return;
            }
        }
        this.shoppingCart.add(new Good(goodName, goodNumber));
    }

    // 查询商品数量
    public int getGoodNumber(String goodName) {
        for (Good good : this.shoppingCart) {
            if (Objects.equals(good.name, goodName)) {
                return good.number;
            }
        }
        return -1;
    }
}

// 商品数据类
class Good {
    String name;
    int number;

    public Good(String name, int number) {
        this.name = name;
        this.number = number;
    }
}