Cookie用法案例-->自动登陆

07020170907

1、cookie是浏览器保存数据的一种形式，数据由服务端产生，通过响应头(setCookie)把数据写入cookie中，浏览器接受到数据后，浏览器将服务器发来的数据存在本地的cookie中

2、cookie的使用步骤：

1)、新创一个Cookie对象：Cookie cookie_username = new Cookie("username", username);

2)、设置Cookie存活时间：cookie_username.setMaxAge(7*24*60*60);[一周]

3)、添加Cookie：response.addCookie(cookie_username);

4)、读取Cookie[]：for (Cookie c : request.getCookies()) { c.getName() + c.getValue() }

3、代码如下：

package com.tiger.servlet;

import java.io.*;
import javax.servlet.*;
import javax.servlet.annotation.*;
import javax.servlet.http.Cookie;
import javax.servlet.http.*;
/**
 * 利用cookie实现自动登陆
 * @author tiger
 * @Date 2017年9月9日
 */
@WebServlet("/createCookie")
public class CreateCookie extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public CreateCookie() { }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    String checkbox = request.getParameter("checkbox");
    if (checkbox != null && checkbox.equals("checkbox")) {
      Cookie cookie_username = new Cookie("username", username);
      cookie_username.setMaxAge(7*24*60*60);
      response.addCookie(cookie_username);
      Cookie cookie_password = new Cookie("password", password);
      cookie_password.setMaxAge(7*24*60*60);
      response.addCookie(cookie_password);
    }
  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doGet(request, response);
  }

}
package com.tiger.servlet;

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.*;
/**
 * 利用cookie实现自动登陆
 * @author tiger
 * @Date 2017年9月9日
 */
@WebServlet("/login")
public class Login extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public Login() { }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    out.println("");
    out.println("");
    out.println("");
    out.println("");
    out.println("---登陆---");
    out.println("");
    out.println("");
    out.println("");
    out.println("

​​");
    Cookie[] cookies = request.getCookies();
    if (cookies != null) {
      for (Cookie cookie : cookies) {
        if (cookie.getName().equals("username")) {
          out.println("姓名：

");
        }
        if (cookie.getName().equals("password")) {
          out.println("密码：

");
        }
      }
      out.println("记住登陆密码：

");
    }else {
      out.println("姓名：

");
      out.println("密码：

");
      out.println("记住登陆密码：

");
    }
    out.println("

");
    out.println("");
  }

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