记录jdbc

Demo01

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
public class Demo01 {
	public static void main(String[] args) {

		//获取连接
		try (Connection conn = DBUtils.getConn();) {
			//创建SQL执行对象
			Statement stat = conn.createStatement();
			//执行SQL
			String sql = "select ename from emp";
			ResultSet rs = stat.executeQuery(sql);
			while(rs.next()) {
				String name = rs.getString("ename");
				System.out.println(name);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Demo02

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class Demo02 {
	public static void main(String[] args) 
			throws IOException {
		//创建读取配置文件数据的对象
		Properties p = new Properties();
		//获取文件流
		InputStream ips = 
			Demo02.class.getClassLoader()
			.getResourceAsStream("jdbc.properties");
		//把文件加载到属性对象中
		p.load(ips);
		//读取数据
		String name = p.getProperty("name");
		String age = p.getProperty("age");
		System.out.println(name+":"+age);
	}
}

Demo03

import java.sql.Connection;
import java.sql.SQLException;

import org.apache.commons.dbcp.BasicDataSource;

public class Demo03 {
	public static void main(String[] args) throws SQLException {
		//创建数据库连接池对象
		BasicDataSource ds = new BasicDataSource();
		//设置数据库连接信息
		ds.setDriverClassName("com.mysql.jdbc.Driver");
		ds.setUrl("jdbc:mysql://localhost:3306/newdb3");
		ds.setUsername("root");
		ds.setPassword("root");
		//设置初始连接数量
		ds.setInitialSize(3);
		//设置最大连接数量
		ds.setMaxActive(5);
		//从连接池中获取连接  抛异常
		Connection conn = ds.getConnection();
		System.out.println(conn);
	}
}

Demo04

import java.sql.Connection;
import java.sql.Statement;
import java.util.Scanner;

public class Demo04 {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.println("请输入用户名");
		String username = s.nextLine();
		System.out.println("请输入密码");
		String password = s.nextLine();
		
		//获取连接
		try (Connection conn = DBUtils.getConn();) {
			Statement stat = conn.createStatement();
			String sql = "select count(*) from user "
					+ "where username='"+username
					+"' and password='"+password+"'";
			//输出后在终端中测试
			System.out.println(sql);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
}

DBUtils

package com.example.demo;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

import org.apache.commons.dbcp.BasicDataSource;

public class DBUtils {
	//创建DBCP连接池.BasicDataSource用池来管理Connection
	private static BasicDataSource ds;
	
	static {
		//创建读取配置文件数据对象
		Properties p=new Properties();
		//获取文件流
		InputStream ips=DBUtils.class.getResourceAsStream("application.yaml");
		try {
			//把文件加载到属性对象中
			p.load(ips);
		} catch (Exception e) {
			//异常打印堆栈跟踪
			e.printStackTrace();
		}
		String driver=p.getProperty("driver");
		String url=p.getProperty("url");
		String username=p.getProperty("username");
		String password=p.getProperty("password");
		//创建数据库连接对象,
		ds=new BasicDataSource();
		//设置数据库连接信息
		ds.setDriverClassName(driver);
		ds.setUrl(url);
		ds.setUsername(username);
		ds.setPassword(password);
		//设置数据库连接数量
		ds.setInitialSize(5);
		//设置最大连接数量
		ds.setMaxActive(100);
	}
	public static Connection getConn() throws Exception {
		Connection conn=ds.getConnection();
		return conn;
		
	}
}