022_jdbc-mysql封装JDBCUtil和抽取数据库配置参数文件

1. 新建一个JDBCProperties工程

2. 编写JDBCUtil.java

package com.lywgames.util;import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties;public class JDBCUtil {private static String driverClass = null;private static String url = null;private static String name = null;private static String password= null;static {try {// 1.创建一个属性配置对象Properties properties = new Properties();// 2.使用类加载器, 去读取src底下的资源文件。对应文件位于src目录底下InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");// 3.导入输入流。properties.load(is);// 4.读取属性driverClass = properties.getProperty("driverClass");url = properties.getProperty("url");name = properties.getProperty("name");password = properties.getProperty("password");} catch (IOException e) {e.printStackTrace();}}/*** 获取连接对象*/public static Connection getConn(){Connection conn = null;try {Class.forName(driverClass);conn = DriverManager.getConnection(url, name, password);} catch (Exception e) {e.printStackTrace();}return conn;}/*** 释放资源* @param conn* @param st* @param rs*/public static void release(Connection conn, Statement st, ResultSet rs){closeRs(rs);closeSt(st);closeConn(conn);}private static void closeRs(ResultSet rs){try {if(rs != null){rs.close();}} catch (SQLException e) {e.printStackTrace();}finally{rs = null;}}private static void closeSt(Statement st){try {if(st != null){st.close();}} catch (SQLException e) {e.printStackTrace();}finally{st = null;}}private static void closeConn(Connection conn){try {if(conn != null){conn.close();}} catch (SQLException e) {e.printStackTrace();}finally{conn = null;}}}

3. 在src目录下编写jdbc.properties属性文件

4. 编写MyJDBC.java使用我们的JDBCUtil.java

package com.lywgames.myjdbc;import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import com.lywgames.util.JDBCUtil;public class MyJDBC {public static void main(String[] args) throws SQLException {// 1.获取连接对象Connection conn = JDBCUtil.getConn(); // 2.创建statement, 跟数据库打交道, 一定需要这个对象Statement st = conn.createStatement();// 3.执行查询sql, 获取ResultSet结果集ResultSet rs = st.executeQuery("select * from user");// 4.使用ResultSet结果集遍历, 下标从1开始while(rs.next()) {System.out.println(rs.getInt(1) + " " + rs.getString(2) + " " + rs.getString(3) + " " + rs.getTimestamp(4));}// 5.释放资源JDBCUtil.release(conn, st, rs);} }

5. 运行结果

总结

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