JDBC（数据库的使用优化）

//传统的读取方式，使用Properties对象的load方法读取
public void test1() throws Exception{
	InputStream in = new FileInputStream("F:\\workspace\\android_web05\\src\\jdbc.properties");
	Properties p = new Properties();
	p.load(in);
	System.out.println(p.get("driver"));
	System.out.println(p.get("url"));
	System.out.println(p.get("username"));
	System.out.println(p.get("password"));
}
//由于路径在服务器端会时时变化，所以使用类的加载器动态获取路径
public void test2() throws Exception{
	//类加载器：加载的是类路径的代码（.class字节码文件所在的目录）
	String path = ReadFileDemo.class.getClassLoader().getResource("jdbc.properties").getPath();
	System.out.println(path);
	InputStream in = new FileInputStream(path);
	Properties p = new Properties();
	p.load(in);
	System.out.println(p.get("driver"));
	System.out.println(p.get("url"));
	System.out.println(p.get("username"));
	System.out.println(p.get("password"));
}
	
//这种方式和第2中方式相似，不过是直接通过类的加载器获得文件的输入流。
public void test3() throws Exception{
	//类加载器：加载的是类路径的代码（.class字节码文件所在的目录）
	InputStream in = ReadFileDemo.class.getClassLoader().getResourceAsStream("jdbc.properties");
	Properties p = new Properties();
	p.load(in);
	System.out.println(p.get("driver"));
	System.out.println(p.get("url"));
	System.out.println(p.get("username"));
	System.out.println(p.get("password"));
}
	
//通过创建ResourceBundle对象来读取配置文件，ResourceBundle底层也是封装了类的加载器专门读取配置文件使用，开发者一般使用这种方法，最为简单。
public void test4() throws Exception{
		
	ResourceBundle rb = ResourceBundle.getBundle("jdbc");//这里直接写文件名，不用加扩展名
	System.out.println(rb.getString("driver"));
	System.out.println(rb.getString("username"));
	System.out.println(rb.getString("password"));
	System.out.println(rb.getString("url"));
	
}

public static void close(Connection conn,Statement stmt,ResultSet rs){
		
		try {
			if(rs!=null){
				rs.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally{
			rs = null;
			try {
				if(stmt!=null){
					stmt.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally{
				stmt = null;
				try {
					if(conn!=null){
						conn.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				} finally{
					conn = null;
				}
			}
		}
	}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;
public class JDBCUtils {
	
	private static String driver = null;
	private static String url = null;
	private static String username = null;
	private static String password = null;
	static{
		ResourceBundle rb = ResourceBundle.getBundle("jdbc");
		driver = rb.getString("driver");
		url = rb.getString("url");
		username = rb.getString("username");
		password = rb.getString("password");
	}
	
	static{
		try {
			Class.forName(driver);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	public static Connection getConnection() throws Exception{
		Connection conn = DriverManager.getConnection(url, username, password);
		return conn;
	}
	
	public static void close(Connection conn,Statement stmt,ResultSet rs){
		
		try {
			if(rs!=null){
				rs.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally{
			rs = null;
			try {
				if(stmt!=null){
					stmt.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally{
				stmt = null;
				try {
					if(conn!=null){
						conn.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				} finally{
					conn = null;
				}
			}
		}
	}
	
}