package util;import java.sql.Connection;
import java.sql.DriverManager;/**** 实现对JDBC 的封装* @author mqy**/
public class JdbcUtil {private JdbcUtil() {}private static String driverClassName = "com,mysql.jdbc.Driver";private static String url = "jdbc:mysql:///jdbcdemo";private static String user = "root";private static String password = "root";//使用静态代码块实现 jdbcUtil的字节码被加载锦jvm中 并且只执行一次。避免每次使用都注册   static{try {Class.forName(DriverClassName);} catch (Exception e) {e.printStackTrace();}}//提供外界访问 public static Connection getConn(){try {return DriverManager.getConnection(url, user, password);} catch (Exception e) {e.printStackTrace();}return null;}
}

    //关闭资源  查询方法关闭资源 JdbcUtil.close(conn,st,rs)//增删改 关闭资源JdbcUtil.close(conn,st,null)public static void close(Connection conn,Statement st,ResultSet rs){try {if (rs != null) {rs.close();}} catch (Exception e) {e.printStackTrace();}finally {try {if (st != null) {st.close();}    } catch (Exception e2) {e2.printStackTrace();}finally {try {if (conn != null) {conn.close();}} catch (Exception e) {e.printStackTrace();}}}}
}

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///jdbcdemo
user=root
password=root;

package util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import com.mysql.jdbc.Statement;/**** 实现对JDBC 的封装* @author mqy**/
public class JdbcUtil {private static    Properties properties = new Properties();//使用静态代码块实现 jdbcUtil的字节码被加载锦jvm中 并且只执行一次。避免每次使用都注册static{try {InputStream inputStream = Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties");properties.load(inputStream);Class.forName(properties.getProperty("driverClassName"));} catch (Exception e) {e.printStackTrace();}}private JdbcUtil() {}//提供外界访问 返回数据库的连接对象public static Connection getConn(){try {return DriverManager.getConnection(properties.getProperty("url"), properties.getProperty("user"), properties.getProperty("password"));} catch (Exception e) {e.printStackTrace();}return null;}    //关闭资源  查询方法关闭资源 JdbcUtil.close(conn,st,rs)//增删改 关闭资源JdbcUtil.close(conn,st,null)public static void close(Connection conn,Statement st,ResultSet rs){try {if (rs != null) {rs.close();}} catch (Exception e) {e.printStackTrace();}finally {try {if (st != null) {st.close();}    } catch (Exception e2) {e2.printStackTrace();}finally {try {if (conn != null) {conn.close();}} catch (Exception e) {e.printStackTrace();}}}}
}