Instance of database connection

Question

People, I have a problem which is this, my database connection class is a Singleton. It happens that if the server drops the instance of the class does not know that the server is down, I only know when, for example, I try to run a resultset from there gives exception. How can I make the connection class instance know that the server has crashed?

Answer 1

I didn’t quite understand your question, but I think I can help you by showing you how I made my connection to my database via JDBC Java.

package com.mypet.MyPet.persistence;

import com.mysql.jdbc.Connection;

import java.sql.DriverManager;
import java.sql.SQLException;

public class ConectionMySql {

    private static final String URL = "jdbc:mysql://127.0.0.1:3306/MyPet?autoReconnect=true&useSSL=false";
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String LOGIN = "root";
    private static final String PASSWORD = "toor";
    public static Connection connection;

    private ConectionMySql(){}

    public static void openConection(){
        try{
            Class.forName(DRIVER);
            ConectionMySql.connection = (Connection) DriverManager.getConnection(URL, LOGIN, PASSWORD);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }

    public static void closeConection(){
        try {
            if(!ConectionMySql.connection.isClosed()){
                connection.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

This is my class that I make the connection with Mysql Bank, I have a way to open and close the connection with the bank, giving a try catch.

Whenever I go to make some call in the bank via Java, I open the connection with the method openConection and close with the closeConection, so in case of any error in connection the application will be aware as it always opens and closes before each call.

public T insert(T object) {
        ConectionMySql.openConection();
        try {
            PreparedStatement preparedStatement = (PreparedStatement) ConectionMySql.connection.prepareStatement(insertSQL, Statement.RETURN_GENERATED_KEYS);
            this.setStatementValuesToInsert(preparedStatement, object);
            preparedStatement.executeUpdate();
            ResultSet resultSet = preparedStatement.getGeneratedKeys();
            if (resultSet.next()){
                object = this.prepareObjectToResponse(resultSet.getLong(1), object);
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        } finally {
            ConectionMySql.closeConection();
        }
        return object;
    }

Where you can see the ConectionMySql.openConection(); and in Finally the ConectionMySql.closeConection();.

I hope to have helped in some way, if you want, can access the code above in my Github in the school project Mypet, Made Back in Java with Spring and JDBC.