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java - servlet 到 JSP 以及 JSP 到 servlet 上的变量

转载 作者：行者123 更新时间：2023-12-01 09:32:21 25 4
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我有一个作业，是使用 jsp 和 servlet 创建剪刀石头布的基本练习。在index.html 上，我创建了一个表单来接收“Rock”、“Paper”或“Scissors”。这将进入一个 Servlet，用于计算回合数、失败数、胜利数和平局数。

一旦您提交了您的移动，无论是石头、布还是剪刀，您将被引导到一个 JSP，该 JSP 将显示记分牌和服务器的移动，但在此 JSP 上有一个表单，其中一个是返回索引的链接.html ，回合、胜利、失败计数器继续计数，然后有一个按钮，它是一个重置按钮，应该将所有值变成 0，这是 jsp 上的不同形式，具有不同的操作。我的老师建议制作两个 servlet，但他说如果我能制作一个 servlet 就可以了，但是制作两个 servlet 会更容易。

摘要:如何从一个 servlet 重置另一个 servlet 上的变量？

index.html:

<html>
<head>
    <title>Actividad 4</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
    <h1>Rock Paper Scissors Game</h1>
    <p>Choose your attack: </p>
    <form method="post" action="move.do">
        <select name="attack">
            <option value="1">Rock</option>
            <option value="2">Scissors</option>
            <option value="3">Paper</option>
        </select>
        <button type="submit">Attack!</button>
    </form>
</body>

web.xml:

<?xml version="1.0" encoding="UTF-8"?>

http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd” 版本=“3.1”> 30 Servlet 行为 4 服务程序 Servlet 行为 4 /move.do 

<servlet>
    <servlet-name>Servlet2 Act 4</servlet-name>
    <servlet-class>Servlet2</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Servlet2 Act 4</servlet-name>
    <url-pattern>/reset.do</url-pattern>
    <init-param>
        <param-name>turn</param-name>
        <param-value>1</param-value>
    </init-param>
</servlet-mapping>

第一个 servlet:

import java.io.IOException;

import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author maple
 */
@WebServlet(name = "Servlet Act 4", urlPatterns = {"/Servlet"})
public class Servlet extends HttpServlet {
    static int turn = 1;
    static int wins = 0;
    static int defeat = 0;
    static int ties = 0;

/**
 * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
 * methods.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {
        /* TODO output your page here. You may use following sample code. */
        out.println("<!DOCTYPE html>");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Servlet Servlet</title>");            
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>Servlet Servlet at " + request.getContextPath() + "</h1>");
        out.println("</body>");
        out.println("</html>");
    }
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
 * Handles the HTTP <code>GET</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    processRequest(request, response);
}

/**
 * Handles the HTTP <code>POST</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    int attack = Integer.parseInt(request.getParameter("attack"));
    int move = randMove();
    String counter = "";
    String decision = "";
    //Checa el metodo randMove(), obtengo un numero aleatorio entre 1 a 3 que lo convierto en
    //Rock = Piedra
    //Scissor = Tijera
    //Paper = Papel
    switch(move) {
        case 1: counter = "Rock";
        break;
        case 2: counter = "Scissor";
        break;
        case 3: counter = "Paper";
        break;
    }

    //Este if comparo que si los dos son iguales, el piedra papel o tijera del servidor
    //Y el piedra papel tijera del jugador para determinar el ganador.
    if(attack == move) {
        ties++;
        decision = "It's a tie!";
    } else if (attack == 1) {
        switch(move){
            case 2: decision = "Player wins!";
            wins++;
            break;
            case 3: decision = "Server wins!";
            defeat++;
            break;
        }
    } else if (attack == 2) {
        switch(move){
            case 1: decision = "Server wins!";
            defeat++;
            break;
            case 3: decision = "Player wins!";
            wins++;
            break;
        }
    } else if (attack == 3) {
        switch(move) {
            case 1: decision = "Player wins!";
            wins++;
            break;
            case 2: decision = "Server wins!";
            defeat++;
            break;
        }
    }

    //Esto es para mantener cuenta que turno es, que movimiento hizo, quien gano, cuantas veces
    //gano quien y perdio quien.
    request.setAttribute("turn", turn);
    request.setAttribute("counter", counter);
    request.setAttribute("winner", decision);
    request.setAttribute("ties", ties);
    request.setAttribute("wins", wins);
    request.setAttribute("defeat", defeat);
    if(turn < 5) {
        turn++;
    } else {
        turn = 1;
        ties = 0;
        wins = 0;
        defeat = 0;
    }
    RequestDispatcher view = 
            request.getRequestDispatcher("Scoreboard.jsp");
    view.forward(request, response);
}

/**
 * Returns a short description of the servlet.
 *
 * @return a String containing servlet description
 */
@Override
public String getServletInfo() {
    return "Short description";
}// </editor-fold>

public static int randMove() {
    int min = 1;
    int max = 3;
    Random rand = new Random();
    int randomNum = rand.nextInt((max - min) + 1) + min;

    return randomNum;
}

}

JSP:

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page import="java.util.*" %>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Scoreboard</title>
    </head>
    <body>
        <h1>Server: <%=request.getAttribute("counter")%></h1>
        <h3>Round <%=request.getAttribute("turn")%> of 5</h3>
        <p><%=request.getAttribute("winner")%></p>
        <table>
            <thead>
                <tr>
                    <td></td>
                    <td>Win</td>
                    <td>Defeat</td>
                    <td>Tie</td>
                </tr>
            </thead>
            <tbody>
                <tr>
                    <td>Player</td>
                    <td><%=request.getAttribute("wins")%></td>
                    <td><%=request.getAttribute("defeat")%></td>
                    <td><%=request.getAttribute("ties")%></td>
                </tr>
                <tr>
                    <td>Server</td>
                    <td><%=request.getAttribute("defeat")%></td>
                    <td><%=request.getAttribute("wins")%></td>
                    <td><%=request.getAttribute("ties")%></td>
                </tr>
            </tbody>
        </table>
        <form method="get" action="reset.do">
            <a type="button" href="index.html">Next round</button></a>
            <button type="submit">Reset</button>
        </form>
    </body>
</html>

最佳答案

变量turn、wins、feat 和tie都是静态的，所以如果你想在另一个servlet中进行更改，只需将它们声明为public，然后用如下代码修改它们

 Servlet.turn = 0

但这不是维护 servlet 状态的正确方法，如果您跨请求声明，您应该使用如下代码将它们保存到 session 中:

request.getSession().setAttribute("turn",0);

关于java - servlet 到 JSP 以及 JSP 到 servlet 上的变量，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/39303376/

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