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

/**
 * 提供获取连接和释放资源的方法
 */
public class JDBCUtils_V3 {
	private static String driver;
	private static String url;
	private static String username;
	private static String password;

	/*
	 * 静态代码块加载配置文件信息
	 */
	static {

		try {
			// 1.通过当前类获取类加载器
			ClassLoader classLoader = JDBCUtils_V3.class.getClassLoader();
			// 2.通过类加载器的方法获得一个输入流
			InputStream is = classLoader.getResourceAsStream("db.properties");
			// 3.创建一个properties对象
			Properties props = new Properties();
			// 4.加载输入流
			props.load(is);
			// 5.获取相关参数的值
			driver = props.getProperty("driver");
			url = props.getProperty("url");
			username = props.getProperty("username");
			password = props.getProperty("password");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	/**
	 * 获取连接方法
	 * 
	 * @return
	 */
	public static Connection getConnection() {
		Connection conn = null;
		try {
			Class.forName(driver);
			conn = DriverManager.getConnection(url, username, password);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return conn;
	}

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

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.junit.Test;

import cn.itheima.jdbc.JDBCUtils_V1;
import cn.itheima.jdbc.JDBCUtils_V2;
import cn.itheima.jdbc.JDBCUtils_V3;

/**
 * 测试工具类
 */
public class TestUtils {

	/*
	 * 根据id更新信息方法
	 */
	@Test
	public void testUpdateyId() {
		Connection conn = null;
		PreparedStatement pstmt = null;

		try {
			// 1.获取连接
			conn = JDBCUtils_V3.getConnection();
			// 2.编写sql语句
			String sql = "update tbl_user set upassword=? where uid=?";
			// 3.获取执行sql语句对象
			pstmt = conn.prepareStatement(sql);
			// 4.设置参数
			pstmt.setString(1, "999");
			pstmt.setInt(2, 1);
			// 5.执行更新操作
			int row = pstmt.executeUpdate();
			if (row > 0) {
				System.out.println("更新成功！");
			} else {
				System.out.println("更新失败！");
			}
			// 释放资源放在此处行么？【不行滴！】
		} catch (Exception e) {
			throw new RuntimeException(e);
		} finally {
			// 6.释放资源
			JDBCUtils_V2.release(conn, pstmt, null);
		}
	}

	/*
	 * 根据id删除信息方法
	 */
	@Test
	public void testDeleteById() {
		Connection conn = null;
		PreparedStatement pstmt = null;

		try {
			// 1.获取连接
			conn = JDBCUtils_V3.getConnection();
			// 2.编写sql语句
			String sql = "delete from tbl_user where uid=?";
			// 3.获取执行sql语句对象
			pstmt = conn.prepareStatement(sql);
			// 4.设置参数
			pstmt.setInt(1, 3);
			// 5.执行删除操作
			int row = pstmt.executeUpdate();
			if (row > 0) {
				System.out.println("删除成功！");
			} else {
				System.out.println("删除失败！");
			}
			// 释放资源放在此处行么？【不行滴！】
		} catch (Exception e) {
			throw new RuntimeException(e);
		} finally {
			// 6.释放资源
			JDBCUtils_V2.release(conn, pstmt, null);
		}
	}

	/*
	 * 添加用户信息方法
	 */
	@Test
	public void testAdd() {
		Connection conn = null;
		PreparedStatement pstmt = null;

		try {
			// 1.获取连接
			conn = JDBCUtils_V2.getConnection();
			// 2.编写sql语句
			String sql = "insert into tbl_user values(null,?,?)";
			// 3.获取执行sql语句对象
			pstmt = conn.prepareStatement(sql);
			// 4.设置参数
			pstmt.setString(1, "lisi");
			pstmt.setString(2, "lisi");
			// 5.执行插入操作
			int row = pstmt.executeUpdate();
			if (row > 0) {
				System.out.println("添加成功！");
			} else {
				System.out.println("添加失败！");
			}
			// 释放资源放在此处行么？【不行滴！】
		} catch (Exception e) {
			throw new RuntimeException(e);
		} finally {
			// 6.释放资源
			JDBCUtils_V2.release(conn, pstmt, null);
		}
	}

	/**
	 * 根据id查询用户信息
	 */
	@Test
	public void testFindUserById() {
		Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		try {
			// 1.获取连接
			conn = JDBCUtils_V1.getConnection();
			// 2.编写sql语句
			String sql = "select * from tbl_user where uid=?";
			// 3.获取执行sql语句对象
			pstmt = conn.prepareStatement(sql);
			// 4.设置参数
			pstmt.setInt(1, 1);
			// 5.执行查询操作
			rs = pstmt.executeQuery();
			// 6.处理结果集
			while (rs.next()) {
				System.out.println(rs.getString(2) + "----" + rs.getString("upassword"));
			}
			// 释放资源放在此处行么？【不行滴！】
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			// 7.释放资源
			JDBCUtils_V1.release(conn, pstmt, rs);
		}
	}
}