WebのJDBC接続

/*
 *   Connection
* 1.       
* 2.      
* 3.   Connection
*/
String driverClassName = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/ea";
String username = "root";
String password = "root";
//      
Class.forName(driverClassName);
//   DriverManager，     3   ，  Connection
Connection con = DriverManager.getConnection(url, username, password);

ステップアップ

JdbcUtils.java
public class JdbcUtils {
   private static Properties props = null;
   //   JdbcUtils         ！
   static {
       //  props     ，   dbconfig.properties   props   
       try {
           InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("dbconfig.properties");
           props = new Properties();
           props.load(in);
       } catch(IOException e) {
           throw new RuntimeException(e);
       }
       //      
       try {
           Class.forName(props.getProperty("driverClassName"));
       } catch (ClassNotFoundException e) {
           throw new RuntimeException(e);
       }
   }
   
   //     !
   public static Connection getConnection() throws SQLException {
       //   Connection
       return DriverManager.getConnection(props.getProperty("url"),
               props.getProperty("username"), 
               props.getProperty("password"));
   }
}

使用

@Test
public void fun1() throws SQLException {
    Connection con = JdbcUtils.getConnection();
    System.out.println(con);
    Connection con1 = JdbcUtils.getConnection();
    System.out.println(con1);
}