Servle之Cookie

Posted 2020-08-31

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
       "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录网页</title>
</head>
    <body>
        <form action="login.do" method="post">
            名称：<input type="text" name="user"><br>
            密码：<input type="password" name="passwd"><br>
            自动登录：<input type="checkbox" name="login" value="auto"><br>
            <input type="submit" value="发送">
        </form>
    </body>
</html>

package cc.openhome;

import java.io.*;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//直接访问index.do  如果cookie中的确有信息  则可以直接登录
@WebServlet("/index.do")
public class Index extends HttpServlet {
    protected void processRequest(HttpServletRequest request,
                                HttpServletResponse response)
                       throws ServletException, IOException {
     
        Cookie[]cookies=request.getCookies();
        if(cookies!=null)
        {
            for(Cookie cookie:cookies)
            {
                String name=cookie.getName();
                String value=cookie.getValue();
                
                if("user".equals(name)&&"caterpillar".equals(value))
                {
                    request.setAttribute(name, value);
                    request.getRequestDispatcher("/user.view").forward(request, response);
                    return;
                }
            }
        }

        response.sendRedirect("login.html");
    }

    @Override
    protected void doGet(HttpServletRequest request,
                         HttpServletResponse response)
                             throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request,
                          HttpServletResponse response)
                            throws ServletException, IOException {
        processRequest(request, response);
    }
}


import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//第一次登录  如果有使用登录会保存cookie
@WebServlet("/login.do")
public class Login extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request,
                         HttpServletResponse response)
                      throws ServletException, IOException {
        String user = request.getParameter("user");
        String passwd = request.getParameter("passwd");
        if("caterpillar".equals(user) && "123456".equals(passwd)) {
            String login = request.getParameter("login");
         
            if("auto".equals(login))
            {
            	Cookie cookie=new Cookie("user", "caterpillar");
            	cookie.setMaxAge(7*24*60*60);
            	response.addCookie(cookie);
            }
            request.setAttribute("user", user);
            request.getRequestDispatcher("user.view")
                    .forward(request, response);
        }
        else {
            response.sendRedirect("login.html");
        }
    }
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    	doPost(req, resp);
    }
}

package cc.openhome;

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//这里先不使用jsp
@WebServlet("/user.view")
public class User extends HttpServlet {

    protected void processRequest(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");

        if(request.getAttribute("user") == null) {
            response.sendRedirect("login.html");
        }

        PrintWriter out = response.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC ‘-//W3C//DTD HTML 4.01" +
                    " Transitional//EN‘>");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Servlet User</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>"
                + request.getAttribute("user") + "已登录</h1>");
        out.println("</body>");
        out.println("</html>");
        out.close();
    }

    @Override
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }
}

当然这里的账号密码是事先设计好的实际开发中应该学会变通从数据库读取信息

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