Servlet通过Cookie保存用户信息，实现自动登录的demo.

开始界面HTML，跳转到判断是否有Cookie的Servlet.

SessionStartPage.html

判断是否有Cookie的Servlet.此处获取Cookie的数据。

package cc.session;

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


/**
 * Servlet implementation class Index
 */
@WebServlet("/sessionindex.do")
public class Index extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Index() {
        super();
        // TODO Auto-generated constructor stub
    }
    
    protected void processRequest(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException
    {
    	Cookie[] cookies=request.getCookies();//查询浏览器存储的本地Cookie,返回结果是数组。
		if(cookies!=null)
		{
			for(Cookie cookie:cookies)
			{//Cookie由name和value两部分组成
				String name=cookie.getName();
				String value=cookie.getValue();
				if("user".equals(name)&&"Daniel".equals(value)) {
					request.setAttribute(name,value );
					request.getRequestDispatcher("/sessionuser.view").forward(request, response);
					return;
				}
			}
		}
		response.sendRedirect("SessionLogin.html");
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//doGet(request, response);
		processRequest(request,response);
		
	}

}

登录界面的Html

SessionLogin.html

	
		
		
	
	
		

			名称

			密码

			自动登录：

			
		
	

登录的Servlet，此处创建Cookie,并将用户存到Cookie中。

package cc.session;

import java.io.IOException;
import java.net.URLDecoder;

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;

/**
 * Servlet implementation class SessionLogin
 */
@WebServlet("/sessionlogin.do")
public class SessionLogin extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SessionLogin() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//doGet(request, response);
		request.setCharacterEncoding("UTF-8");
		String user=URLDecoder.decode(request.getParameter("user"),"UTF-8");
		String password=request.getParameter("password");
		String autologin=request.getParameter("autologin");
		if(user.equals("Daniel")&&password.equals("2018Daniel"))
		{
			if("auto".equals(autologin))
			{//自动登录时，创建Cookie,保存用户名。
				Cookie cookieLogin=new Cookie("user", user);
				cookieLogin.setMaxAge(3*60);//设置保存时间为3分钟
				response.addCookie(cookieLogin);
			}
			request.setAttribute("user", user);
			request.setAttribute("password",password);
			request.getRequestDispatcher("sessionuser.view").forward(request, response);
		}
		else {
			response.sendRedirect("SessionLogin.html");
		}
	
	}

}

获取Cookie和登录成功后的Servlet

package cc.session;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class SessionUser
 */
@WebServlet("/sessionuser.view")
public class SessionUser extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SessionUser() {
        super();
        // TODO Auto-generated constructor stub
    }
    private void processRequest(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException {
 
		String user=(String) request.getAttribute("user");//forward过来的request,需要通过getAttribute方法获得，不是getParameter
		PrintWriter out= response.getWriter();
		if(user==null)
		{
			response.sendRedirect("SessionLogin.html");
		}
		else {
			out.println(""+user+"  Welcome!");
		}
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		//processRequest(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//doGet(request, response);
		processRequest(request,response);
		
	}

}