jdbc学习(一): 利用配置文件、接口等方式建立数据库连接

今天学习了用配置文件和实现接口等方式来访问数据库。

知识点1. 采用系统api的properties方法来加载配置文件，根据Key，value方式来读取数据库配置信息, driver, url, username, password。

知识点2. 使用接口方式来实现获得数据库连接以及关闭连接

后续还将学习数据库访问连接池等技术。

上述的代码都来自与java学习笔记.

/**
 * 
 */
package db;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;

/**
 * 数据库连接测试类
 * 1. dbsource 实例化
 * 2. 获得connection
 * 3. 根据connection是否关闭的状态，打印相应的状态语句
 * @author Administrator
 *
 */
public class ConnectionDemo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		DBSource dbSource;
		try {
			dbSource = new SimpleDBSource();
			Connection conn = dbSource.getConnect();
			
			if( !conn.isClosed()){
				System.out.println("数据库连接开启!");
			}
			
			dbSource.closeConn(conn);
			
			if(conn.isClosed()){
				System.out.println("数据库连接关闭");
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}

}

package db;

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

/**
 * 接口类
 * getConnection()
 * closeConn()
 * @author sean
 *
 */
public interface DBSource {
	public Connection getConnect() throws SQLException;
	public void closeConn(Connection conn) throws SQLException;

}

/**
 * 
 */
package db;

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

/**
 * @author sean
 * 
 * 构造函数
 * 加载配置文件、赋值、加载驱动程序
 * 获得数据库连接getConn
 * 关闭数据库连接close()
 *
 */
public class SimpleDBSource implements DBSource{
	
	private String url;
	private String username;
	private String password;
	private Properties props;

	/**
	 * 构造函数
	 * 加载配置文件
	 * @throws FileNotFoundException
	 * @throws IOException
	 * @throws ClassNotFoundException
	 */
	public SimpleDBSource() throws FileNotFoundException, IOException, ClassNotFoundException{
		this("jdbc.properties");
	}
	
	/**
	 * 1. 初始化Properties, 2. loadfile, 3. assignment
	 * @param configFile
	 * @throws FileNotFoundException
	 * @throws IOException
	 * @throws ClassNotFoundException
	 */
	public SimpleDBSource(String configFile) throws FileNotFoundException, IOException, ClassNotFoundException{
		//TODO 1. 初始化Properties, 2. loadfile, 3. assignment
		props = new Properties();
		
		props.load(new FileInputStream(configFile));
		
		url = props.getProperty("net.tuolian.url");
		username = props.getProperty("net.tuolian.username");
		password = props.getProperty("net.tuolian.password");
		
		Class.forName(props.getProperty("net.tuolian.Driver"));
	}
	
	/**
	 * 获得数据库连接Connection
	 */
	public Connection getConnect() throws SQLException {
		// TODO Auto-generated method stub
		return DriverManager.getConnection(url, username, password);
	}

	/**
	 * 关闭当前连接
	 */
	public void closeConn(Connection conn) throws SQLException {
		// TODO Auto-generated method stub
		if( conn == null){
			return;
		}		
		conn.close();
	}
}

net.tuolian.Driver=com.mysql.jdbc.Driver
net.tuolian.url=jdbc:mysql://localhost:3306/demo
net.tuolian.username=root
net.tuolian.password=root