JAVA基础之ServletContext应用

创建一个登陆的界面，并且统计次数！

导入jar包;

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 {
        // 获取ServletContext对象
        ServletContext context = getServletContext();
        // 定义计数器
        int count = 0;
        // 将计数器存入ServletContext对象中
        context.setAttribute("count", count);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 获取请求参数
        String uname = request.getParameter("username");
        // 获取密码
        String pwd = request.getParameter("pwd");
        // 调用Service登录方法
        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);
        //赋值
        pst.setString(1, uname);
        pst.setString(2, pwd);
        //执行sql
        ResultSet rs=pst.executeQuery();
        //处理结果集
        int row =0;
        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>

（自动）

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;
        //创建properties集合
        Properties pro=new Properties();
                try {
//                    //明确数据源
//                    FileInputStream fis=new FileInputStream("src/db.properties");
//                    //将properties中的减值对读取到properties集合中
//                    pro.load(fis);
                    //1.注册驱动(静态方法)(包名+类名）
                    Class.forName("com.mysql.jdbc.Driver");
                    //2.获取连接对象(导包都导sql里面的，不导jdbc里的；多态！报异常是因为用户输入的串可能写错）后面设置下数据格式
                    String url="jdbc:mysql://localhost:3306/java0603?useUnicode=true&characterEncoding=UTF-8";
                    String user="root";
                    String password="123456";
                    conn=DriverManager.getConnection(url,user,password);
                } catch (ClassNotFoundException | SQLException  e) {
                    // TODO Auto-generated catch block
                    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>