Cookie案例：簡單登錄界面中的應用

ServletDemo1.java

package ztq.servlet.study;

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 ServletDemo1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //設置服務器端以UTF-8編碼進行輸出
        response.setCharacterEncoding("UTF-8");
        //設置瀏覽器以UTF-8編碼進行接收，解決中文亂碼問題
        response.setContentType("text/html;charset = UTF-8");
        PrintWriter out = response.getWriter();
        
        //獲取cookie
        String username = "";
        String check = "";
        Cookie[] cookies = request.getCookies();
        for(int i = 0; cookies != null && i < cookies.length; i++){
            Cookie c = cookies[i];
            if("username".equals(c.getName())){
                username = c.getValue();
                check = "checked = 'checked'";
                break;
            }
        }
        
        //登錄頁面
        out.write("<form action = '" + request.getContextPath() + "/servlet/ServletDemo2' method = 'post'>");
        out.write("用戶名：<input type = 'text' name = 'username' value = '" + username + "'><br />");
        out.write("密碼：<input type = 'password' name = 'password' value = ''><br />");
        out.write("記住用戶名：<input type = 'checkbox' name = 'remember'" + check + "'><br />");
        out.write("<input type = 'submit' name = 'submit' value = '登錄'><br />");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

 

ServletDemo2.java

package ztq.servlet.study;

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 ServletDemo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String username = request.getParameter("username");
        String remember = request.getParameter("remember");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset = UTF-8");
        PrintWriter out = response.getWriter();
        
        //創建一個新的Cookie
        Cookie cookie = new Cookie("username", username);
        cookie.setPath(request.getContextPath());
        if(remember != null){
            //如果選擇了記住用戶名，則設置Cookie的有效期為一個不為0的整數
            cookie.setMaxAge(Integer.MAX_VALUE);
        }else{
            //否則則把有效期設置為0，即命令瀏覽器刪除該cookie
            cookie.setMaxAge(0);
        }
        //將cookie對象添加到response對象中，這樣服務器在輸出response對象中的內容時就會把cookie也輸出到客戶端服務器
        response.addCookie(cookie);
        out.write("登錄成功！");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

 

結果：

輸入用戶名和密碼，選擇記住用戶名，然后點擊登錄。

 

頁面顯示登錄成功！

 

重新打開瀏覽器，再次訪問登錄界面，會顯示如圖。