JAVA basis of the application ServletContext

Create a login interface, and count the number!

Introducing jar package;

1、

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/java0603?useUnicode=true&characterEncoding=UTF-8
username=root
password=123456

2、

package com.oracle.web;

import java.io.IOException;

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

import com.oracle.service.UserService;

public class LoginServlet extends HttpServlet {
    private UserService userService = new UserService();

    public void init() throws ServletException {
        //Get ServletContext object 
        ServletContext context = GetServletContext ();
         // custom counter 
        int COUNT = 0 ;
         // counter ServletContext object stored in 
        context.setAttribute ( "COUNT" , COUNT); 
    } 
    protected  void the doGet (the HttpServletRequest Request, the HttpServletResponse Response)
             throws ServletException, IOException {
         // get the request parameter 
        String uname = request.getParameter ( "username" );
         // get the password 
        String pwd = request.getParameter ( "pwd" );
         // call the login method Service
        int row = userService.loginUser(uname, pwd);
        if (row > 0) {
            // 登录成功
            // 获取ServletContext对象
            ServletContext context = getServletContext();
            int count = (int) context.getAttribute("count");
            count++;
            context.setAttribute("count", count);
            response.getWriter().write("you are the " + count + " person success");
        } else {
            // 登录失败
            response.getWriter().write("fail");
        }
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

3、

package com.oracle.service;

import java.sql.SQLException;

import com.oracle.dao.UserDao;

public class UserService {
    private UserDao userDao = new UserDao();
    // 用户登录
    public int loginUser(String uname, String pwd) {
        int row = 0;
        try {
            row = userDao.loginUser(uname, pwd);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return row;
    }
}

4、

package com.oracle.dao;

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

import com.oracle.tools.JDBCUtils;

public class UserDao {
    //用户登录
    public int loginUser(String uname,String pwd) throws SQLException{
        Connection conn=JDBCUtils.getConn();
        String sql="select count(*) from user where uname=? and pwd=?";
        PreparedStatement pst=conn.prepareStatement(sql);
        // Assignment 
        pst.setString (. 1 , the uname); 
        pst.setString ( 2 , pwd);
         // execute SQL 
        the ResultSet RS = pst.executeQuery ();
         // result set 
        int Row = 0 ;
         the while (rs.next ( )) { 
            Row = rs.getInt (. 1 ); 
        } 
        return Row; 
    } 
    

}

5、

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>WEB04</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>MyServlet</display-name>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>com.oracle.demo01.MyServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>MyServlet</servlet-name>
    <url-pattern>/MyServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>LoginServlet</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.oracle.web.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>Servlet01</display-name>
    <servlet-name>Servlet01</servlet-name>
    <servlet-class>com.oracle.demo01.Servlet01</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Servlet01</servlet-name>
    <url-pattern>/Servlet01</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>Servlet02</display-name>
    <servlet-name>Servlet02</servlet-name>
    <servlet-class>com.oracle.demo01.Servlet02</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Servlet02</servlet-name>
    <url-pattern>/Servlet02</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>Serlvlet03</display-name>
    <servlet-name>Serlvlet03</servlet-name>
    <servlet-class>com.oracle.demo01.Serlvlet03</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Serlvlet03</servlet-name>
    <url-pattern>/Serlvlet03</url-pattern>
  </servlet-mapping>
</web-app>

(automatic)

6、

package com.oracle.tools;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtils {
    //获取连接对象的方法(静态的）
//    public static void main(String[] args) {
//        Connection conn=getConn();
//        System.out.println (Conn);
 //     } 
    public  static   Connection getConn () { 
        Connection Conn = null ;
         // Create a set of properties 
        the Properties Pro = new new the Properties ();
                 the try {
 //                     // clear the data source
 //                     the FileInputStream FIS the FileInputStream new new = ( "the src / the db.properties");
 //                     // the properties of the impairment reading to the properties set
 //                     pro.load (FIS);
                     // 1. Register drive (static method) ( package name + class name) 
                    the Class.forName ( "com.mysql.jdbc.Driver");
                     // 2. Get the connection object (sql guide package are turned inside, in the non-conducting jdbc; polymorphism reported abnormal because the string entered by the user may be wrong) is provided behind the data format! 
                    String URL = "jdbc: MySQL: // localhost: 3306 / java0603 useUnicode = & characterEncoding = UTF-to true. 8 "? ; 
                    String User =" the root " ; 
                    String password =" 123456 " ; 
                    Conn = the DriverManager.getConnection (URL, User, password); 
                } the catch (a ClassNotFoundException | SQLException E) {
                     // the TODO Auto-Generated Block the catch 
                    e.printStackTrace (); 
                } 
                return conn;    
    }
    //释放资源
    public static void close(Connection conn,Statement sta){
        if(sta!=null){
            try {
                sta.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
    //释放资源2
    public static void close(Connection conn,Statement sta,ResultSet rs){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(sta!=null){
            try {
                sta.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

7、

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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>Insert title here</title>
</head>
<body>
    <form action="/WEB04/LoginServlet" method="post">
        用户名:<input type="text" name="username"><br> 
        密码；<input type="password" name="pwd"><br> 
        <input type="submit" value="登录">
    </form>
</body>
</html>

JAVA basis of the application ServletContext

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