JDBC_获取数据库连接

<span style="font-size:24px;">package src.com.jdbc.java;

import java.io.IOException;
import java.io.InputStream;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

import org.junit.Test;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Driver;

public class JDBCTest {
	@Test
	public void testGetConnection2() throws Exception{
		System.out.println(getConnection2());
	}
	public Connection getConnection2() throws Exception{
		//1、准备连接数据库的四个字符
		//1)、创建properties对象
		Properties properties=new Properties();
		
		//2)、获取jdbc.properties对象
		InputStream in=this.getClass().getClassLoader().getResourceAsStream("jdbc.properties");
		
		//3)、加载2）对应的输入流
		properties.load(in);
		//4)、具体决定user，passwrod等四个字符串
		String user=properties.getProperty("user");
		String password=properties.getProperty("password");
		String jdbcUrl=properties.getProperty("jdbcUrl");
		String driver=properties.getProperty("driver");
		
		//2、加载数据库驱动程序(对应的 Driver 实现类中有注册驱动的静态代码块.)
		Class.forName(driver);
		//3、通过DriverManager的getConnection()方法获取数据库的连接。
		return (Connection) DriverManager.getConnection(jdbcUrl,user,password);
	}
	/**
	 * DriverManager 是驱动的管理类. 
	 * 1、可以通过重载的getconnection()方法获取连接，
	 * 2、可以同时管理多个驱动程序；注册了多个数据库连接，则调用getconnection()方法
	 * 时传入的参数不同，即返回不同的数据库连接
	 * @throws IOException 
	 * @throws ClassNotFoundException 
	 * @throws SQLException 
	 * 
	 */
	@Test
	public void testDriverManager() throws Exception{
		//1、准备连接数据库的四个字符
		String driverClass = null;
		String jdbcUrl = null;
		String user = null;
		String password = null;
		// 读取类路径下jdbc.properties
		InputStream in = getClass().getClassLoader().getResourceAsStream(
				"jdbc.properties");
		Properties properties = new Properties();
		properties.load(in);
		driverClass = properties.getProperty("driver");
		jdbcUrl = properties.getProperty("jdbcUrl");
		user = properties.getProperty("user");
		password = properties.getProperty("password");
		//2、加载数据库驱动程序(对应的 Driver 实现类中有注册驱动的静态代码块.)
		Class.forName(driverClass);
		//3、通过DriverManager的getConnection()方法获取数据库的连接。
		Connection connection=(Connection) DriverManager.getConnection(jdbcUrl,user,password);
		System.out.println(connection);
	}
	@Test
	public void testDriver() throws SQLException {
		Driver driver = new com.mysql.jdbc.Driver();
		String url = "jdbc:mysql://127.0.0.1:3306/cjl";
		Properties info = new Properties();
		info.put("user", "root");
		info.put("password", "root123");
		Connection connection = (Connection) driver.connect(url, info);
		System.out.println(connection);

	}

	/**
	 * 编写一个通用方法：把数据库驱动Driver实现类的全类名、URL、user、password放入
	 * 一个配置文件中，通过修改配置文件的方式实现和具体的数据库解偶
	 * 
	 * @throws Exception
	 */
	public Connection getConnection() throws Exception {
		String driverClass = null;
		String jdbcUrl = null;
		String user = null;
		String password = null;
		// 读取类路径下jdbc.properties
		InputStream in = getClass().getClassLoader().getResourceAsStream(
				"jdbc.properties");
		Properties properties = new Properties();
		properties.load(in);
		driverClass = properties.getProperty("driver");
		jdbcUrl = properties.getProperty("jdbcUrl");
		user = properties.getProperty("user");
		password = properties.getProperty("password");
		//通过反射创建Driver对象
		Driver driver = (Driver) Class.forName(driverClass).newInstance();

		Properties info = new Properties();
		info.put("user", user);
		info.put("password", password);
		//通过Driver的connection方法获取数据库连接
		Connection connection = (Connection) driver.connect(jdbcUrl, info);
		return connection;
	}
	@Test
	public void testGetConnection() throws Exception{
		System.out.println(getConnection());
	}

}
</span>

jdbc.properties文件中的配置

driver=com.mysql.jdbc.Driver
jdbcUrl=jdbc:mysql://127.0.0.1:3306/cjl
user=root
password=root123