Servlet登錄註銷Cookies實例

Cookie是存儲在客戶端的一種資訊技術。

在上一頁中，我們學到了很多關於cookie的內容如何創建cookie，如何刪除cookie，如何獲取cookie等

在這裏，我們將使用servlet cookie創建一個登錄和註銷示例。

在這個例子中，我們創建了3個鏈接：登錄，註銷和用戶資料。用戶在未登錄之前不能進入個人資料頁面。如果用戶已經註銷，則需要再次登錄才能訪問個人資料。

在這個應用程式中，創建了以下檔。

index.html - Web應用程式首頁。
link.html - 鏈接頁面。
login.html - 登錄頁面。
LoginServlet.java - 登錄Servlet處理。
LogoutServlet.java - 註銷Servlet處理。
ProfileServlet.java - 用戶個人資料Servlet。
web.xml - Servlet配置檔。

打開Eclipse，創建一個動態Web專案：LoginWithCookies，其完整的專案結構如下圖所示 -

按以下順序，分別編寫每個檔的源代碼。

檔：index.html -

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>使用Cookie登錄應用程式</title>
</head>
<body style="text-algin: center;">
    <h2>歡迎使用Cookie登錄應用程式</h2>
    <a href="login.html">登錄</a>|
    <a href="logout">註銷</a>|
    <a href="profile">個人資訊</a>
</body>
</html>

檔：link.html -

<a href="login.html">登錄</a>|
<a href="logout">註銷</a>|
<a href="profile">個人資訊</a>
<hr>

檔：login.html -

    <div style="text-algin: center; padding-top:12px;">
        <form action="login" method="post">
            用戶名：<input type="text" name="name">  密碼：<input type="password"
                name="password"><input type="submit" value="登錄">
        </form>
    </div>
</body>
</html>

檔：LoginServlet.java -

package com.zaixian;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("UTF-8");
        PrintWriter out = response.getWriter();
        request.getRequestDispatcher("link.html").include(request, response);

        String name = request.getParameter("name");
        String password = request.getParameter("password");

        // 用戶名和密碼分別為：admin , 123456
        if (name.equals("admin") && password.equals("123456")) {
            out.print("您已成功登錄系統!");
            out.print("<br>歡迎您, " + name);
            Cookie ck = new Cookie("name", name);
            response.addCookie(ck);
        } else {
            out.print("<font style='color:red;'>用戶名或密碼錯誤!</font>");
            request.getRequestDispatcher("login.html").include(request, response);
        }
        out.close();
    }

}

檔：LogoutServlet.java -

package com.zaixian;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LogoutServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("UTF-8");
        PrintWriter out = response.getWriter();

        request.getRequestDispatcher("link.html").include(request, response);

        Cookie ck = new Cookie("name", "");
        ck.setMaxAge(0);
        response.addCookie(ck);

        out.print("您已成功註銷!");
    }
}

檔：ProfileServlet.java -

package com.zaixian;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ProfileServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("UTF-8");
        PrintWriter out = response.getWriter();

        request.getRequestDispatcher("link.html").include(request, response);

        Cookie ck[] = request.getCookies();
        if (ck != null) {
            String name = ck[0].getValue();
            if (!name.equals("") || name != null) {
                out.print("<b>歡迎您來到個人資訊中心</b>");
                out.print("<br>您好, " + name);
            }
        } else {
            out.print("<font style='color:red;'>請先登錄!</font>");
            request.getRequestDispatcher("login.html").include(request, response);
        }
        out.close();
    }
}

檔：web.xml -

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    id="WebApp_ID" version="3.1">
    <display-name>LoginWithCookies</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
    </welcome-file-list>

    <!-- 登錄Servlet -->
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>com.zaixian.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

    <!-- 註銷Servlet -->
    <servlet>
        <servlet-name>LogoutServlet</servlet-name>
        <servlet-class>com.zaixian.LogoutServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LogoutServlet</servlet-name>
        <url-pattern>/logout</url-pattern>
    </servlet-mapping>

    <!-- 用戶資料Servlet -->
    <servlet>
        <servlet-name>ProfileServlet</servlet-name>
        <servlet-class>com.zaixian.ProfileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ProfileServlet</servlet-name>
        <url-pattern>/profile</url-pattern>
    </servlet-mapping>
</web-app>

在編寫所有上面檔代碼之後，部署這個Web應用程式，打開流覽器訪問URL： http://localhost:8080/LoginWithCookies/ ，如果代碼沒有錯誤，應該會看到以下結果 -