Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之17.Session-阿里云开发者社区

–Session 简介
–Session API
–Session 实例
• 登录Session

#################Michael分割线####################

• Session 简介
–由于HTTP协议的无状态性，无法持久保持对象的状态，那么怎么才能实现持久保存对象的状态呢？

Java的解决方案有两种：
• Cookie
–见上一节
• Session
–Session 是用来跟踪用户当前状态的一种机制，是针对浏览器和服务器的一对一关系。
–Session 的一般用法是，在用户登录时将用户的登录信息保存到session中，以便以后使用。

• Session API
–Session 接口HttpSession
• 通常我们只使用HttpSession接口，接口的实现由web容器来完成
–获得HttpSession
• 可以从HttpServletRequest中获得HttpSession
–request.getSession();
–将信息保存在HttpSession中
• session.setAttribute(“UserSession”,obj);
–从HttpSession中获得信息
• session.getAttribute(“UserSession”);
–使HttpSession失效
• session.invalidate();

SessionServlet.java

package com.michael.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class SessionServlet extends HttpServlet {

 /**
 * Constructor of the object.
 */
 public SessionServlet() {
 super();
 }

 /**
 * Destruction of the servlet. 
 */
 public void destroy() {
 super.destroy(); // Just puts "destroy" string in log
 // Put your code here
 }

 /**
 * The doGet method of the servlet. 
 *
 * This method is called when a form has its tag value method equals to get.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 doPost(request,response);
 }

 /**
 * The doPost method of the servlet. 
 *
 * This method is called when a form has its tag value method equals to post.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 HttpSession session = request.getSession();
 session.setAttribute( "SessionObj", "session_Value");

 response.setContentType( "text/html");
 PrintWriter out = response.getWriter();
 out
 .println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
 out.println("<HTML>");
 out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
 out.println(" <BODY>");
 out.print(" This is ");
 out.print(this.getClass());
 out.println(", using the POST method");
 out.println(" </BODY>");
 out.println("</HTML>");
 out.flush();
 out.close();
 }

 /**
 * Initialization of the servlet. 
 *
 * @throws ServletException if an error occure
 */
 public void init() throws ServletException {
 // Put your code here
 }

}

SessionServlet2.java

package com.michael.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class SessionServlet2 extends HttpServlet {

 /**
 * Constructor of the object.
 */
 public SessionServlet2() {
 super();
 }

 /**
 * Destruction of the servlet. 
 */
 public void destroy() {
 super.destroy(); // Just puts "destroy" string in log
 // Put your code here
 }

 /**
 * The doGet method of the servlet. 
 *
 * This method is called when a form has its tag value method equals to get.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 doPost(request,response);
 }

 /**
 * The doPost method of the servlet. 
 *
 * This method is called when a form has its tag value method equals to post.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 HttpSession session = request.getSession();
 String obj = (String) session.getAttribute( "SessionObj");

 response.setContentType( "text/html");
 PrintWriter out = response.getWriter();
 out
 .println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
 out.println("<HTML>");
 out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
 out.println(" <BODY>");
 out.print(obj);
 out.println(" </BODY>");
 out.println("</HTML>");
 out.flush();
 out.close();
 }

 /**
 * Initialization of the servlet. 
 *
 * @throws ServletException if an error occure
 */
 public void init() throws ServletException {
 // Put your code here
 }

}

看下效果

关闭IE后再打开测试

SessionServlet2.java

• Session 实例
–登录Session

ConnectionUtil.java

package com.michael.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.michael.dao.ConnectionUtil;
import com.michael.dao.User;
import com.michael.dao.UserDao;

public class UserDaoImpl implements UserDao {

         public User login(String username, String password) {
                Connection conn = new ConnectionUtil().openConnection();
                String sql = "select id,name,password from UserTbl where name=? and password=?";
                 try {
                        PreparedStatement pstmt = conn.prepareStatement(sql);
                        pstmt.setString(1, username);
                        pstmt.setString(2, password);
                        ResultSet rs = pstmt.executeQuery();
                         if(rs.next()){
                                 int id = rs.getInt(1);
                                User u = new User();
                                u.setId(id);
                                u.setUsername(username);
                                u.setPassword(password);
                                 return u;
                        }
                } catch (SQLException e) {
                        e.printStackTrace();
                } finally{
                                 try {
                                        conn.close();
                                } catch (SQLException e) {
                                        e.printStackTrace();
                                }
                }
                 return null;
        }

}

User.java

package com.michael.dao;

public class User {
         private int id;
         private String username;
         private String password;
         public int getId() {
                 return id;
        }
         public void setId( int id) {
                 this.id = id;
        }
         public String getPassword() {
                 return password;
        }
         public void setPassword(String password) {
                 this.password = password;
        }
         public String getUsername() {
                 return username;
        }
         public void setUsername(String username) {
                 this.username = username;
        }
}

UserDao.java

package com.michael.dao;

public interface UserDao {
        public User login(String username,String password);
}

UserDaoImpl.java

LoginServlet.java

package com.michael.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.michael.dao.User;
import com.michael.dao.UserDao;
import com.michael.dao.impl.UserDaoImpl;

public class LoginServlet extends HttpServlet {

 /**
 * Constructor of the object.
 */
 public LoginServlet() {
 super();
 }

 /**
 * Destruction of the servlet. 
 */
 public void destroy() {
 super.destroy(); // Just puts "destroy" string in log
 // Put your code here
 }

 /**
 * The doGet method of the servlet. 
 *
 * This method is called when a form has its tag value method equals to get.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 response.setContentType( "text/html");
 PrintWriter out = response.getWriter();
 out.println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
 out.println("<HTML>");
 out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
 out.println(" <BODY>");
 out.print(" This is ");
 out.print(this.getClass());
 out.println(", using the GET method");
 out.println(" </BODY>");
 out.println("</HTML>");
 out.flush();
 out.close();
 }

 /**
 * The doPost method of the servlet. 
 *
 * This method is called when a form has its tag value method equals to post.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 //获取用户名和密码
 String username = request.getParameter("username");
 String password = request.getParameter("password");
 UserDao dao = new UserDaoImpl();
 User u = dao.login(username,password);
 if(u!=null){
 HttpSession session = request.getSession();
 session.setAttribute("UserSession", u);
 request.getRequestDispatcher("/welcome.jsp").forward(request, response);
 }else{
 request.getRequestDispatcher("/failure.html").forward(request, response);
 }
 }

 /**
 * Initialization of the servlet. 
 *
 * @throws ServletException if an error occure
 */
 public void init() throws ServletException {
 // Put your code here
 }

}

DBConfig.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql: //localhost:3306/servlet_db
user=root
password=mysqladmin

#################Michael分割线####################

本文转自redking51CTO博客，原文链接：http://blog.51cto.com/redking/175908，如需转载请自行联系原作者

Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之17.Session

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