driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test
username=root
password=

package com.test;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;public class JdbcUtils {private static String driver = null;private static String url = null;private static String username = null;private static String password = null;// 加载驱动，获取数据库连接信息static {try {// 加载配置文件InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("DB.properties");Properties properties = new Properties();properties.load(in);driver = properties.getProperty("driver");url = properties.getProperty("url");username = properties.getProperty("username");password = properties.getProperty("password");// 加载驱动Class.forName(driver);} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();}}/*** 获取数据库连接* @throws SQLException*/public static Connection getConnection() {try {return DriverManager.getConnection(url, username, password);} catch (SQLException e) {e.printStackTrace();}return null;}/*** 释放资源* @param connection* @param preparedStatement* @param resultSet*/public static void releaseDB(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) {if (connection != null) {try {connection.close();} catch (SQLException e) {e.printStackTrace();}}if (preparedStatement != null) {try {preparedStatement.close();} catch (SQLException e) {e.printStackTrace();}}if (resultSet != null) {try {resultSet.close();} catch (SQLException e) {e.printStackTrace();}}}
}

package com.test;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;public class JdbcTest {public void insert() {Connection connection = null;PreparedStatement preparedStatement = null;try {// 获取连接connection = JdbcUtils.getConnection();// 准备sql语句String sql = "INSERT INTO user(id,name,age) VALUES(?,?,?)";// 获取PrepareStatement对象preparedStatement = connection.prepareStatement(sql);// 填充占位符preparedStatement.setInt(1, 6);preparedStatement.setString(2, "小A");preparedStatement.setInt(3, 25);// 执行sqlint num = preparedStatement.executeUpdate();// 返回影响到的行数System.out.println("一共影响到" + num + "行");} catch (SQLException e) {e.printStackTrace();} finally {JdbcUtils.releaseDB(connection, preparedStatement, null);}}public void update() {Connection connection = null;PreparedStatement preparedStatement = null;try {// 获取连接connection = JdbcUtils.getConnection();// 准备sql语句String sql = "update user set age = ? where name = ?";// 获取PrepareStatement对象preparedStatement = connection.prepareStatement(sql);// 填充占位符         preparedStatement.setInt(1, 30);preparedStatement.setString(2, "小A");// 执行sqlint num = preparedStatement.executeUpdate();// 返回影响到的行数System.out.println("一共影响到" + num + "行");} catch (SQLException e) {e.printStackTrace();} finally {JdbcUtils.releaseDB(connection, preparedStatement, null);}}public void query() {Connection connection = null;PreparedStatement preparedStatement = null;ResultSet resultSet = null;try {connection = JdbcUtils.getConnection();String sql = "SELECT name,age FROM user";preparedStatement = connection.prepareStatement(sql);resultSet = preparedStatement.executeQuery();// 遍历结果集while (resultSet.next()) {String name = resultSet.getString(1);Integer age = resultSet.getInt(2);                System.out.println("name:" + name + ", age:" + age);}} catch (Exception e) {e.printStackTrace();} finally {JdbcUtils.releaseDB(connection, preparedStatement, resultSet);}}public void delete() {Connection connection = null;PreparedStatement preparedStatement = null;try {connection = JdbcUtils.getConnection();String sql = "DELETE FROM user WHERE id = ?";preparedStatement = connection.prepareStatement(sql);preparedStatement.setInt(1, 6);int num = preparedStatement.executeUpdate();System.out.println("一共影响到" + num + "行");} catch (Exception e) {e.printStackTrace();} finally {JdbcUtils.releaseDB(connection, preparedStatement, null);}}}