package jdbc;​import org.junit.jupiter.api.Test;​import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;​public class JDBCUtils {public static Connection connection;private static String url="jdbc:mysql://localhost:3306/aaa?useUnicode=true&characterEncoding=utf-8";private static String username="root";private static String password="root";​static{try {Class.forName("com.mysql.jdbc.Driver");connection = DriverManager.getConnection(url,username,password);​} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}}​public static Connection getConnection(){return connection;}​@Testpublic void test(){Connection connection = JDBCUtils.getConnection();System.out.println(connection);}}

 url=jdbc:mysql://localhost:3306/aaa?useUnicode=true&characterEncoding=utf-8username=rootpassword=root

package jdbc;​import org.junit.jupiter.api.Test;​import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.Properties;​public class JDBCUtils2 {private static Connection connection;private static String url;private static String username;private static String password;​static {try {//动态加载驱动Class.forName("com.mysql.jdbc.Driver");//加载配置文件Properties properties = new Properties();properties.load(new FileInputStream("src/main/java/db.properties"));url = properties.getProperty("url");username = properties.getProperty("username");password = properties.getProperty("password");​connection = DriverManager.getConnection(url,username,password);​​} catch (ClassNotFoundException e) {e.printStackTrace();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}}​public static Connection getConnection(){return connection;}​@Testpublic void test(){Connection connection = JDBCUtils2.getConnection();System.out.println(connection);}}