baza

package com.company;
//package jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

//TODO: insert function
public class JDBC {
    String driver = "com.mysql.cj.jdbc.Driver";
    String url = "jdbc:mysql://hostname:3306/kuku";

    /**Loading driver*/
    static boolean loadDriver() {
        System.out.print("Checking driver...");
        try {
            Class.forName("com.mysql.cj.jdbc.Driver").newInstance();
            return true;
        } catch (Exception e) {
            System.out.println("Error during loading a driver");
            return false;
        }
    }

    /**
     * Method for connecting to database
     *
     * @param address
     *            - address of the database
     * @param dataBaseName
     *            - ..as above
     * @param userName
     *            - login to database
     * @param password
     *            - password to database
     * @return - connects with database
     */
    private static Connection connectToDatabase(String address,
                                                String dataBaseName, String userName, String password) {
        System.out.print("\nConnecting with database..:");
        String database = "jdbc:mysql://" + address + "/" + dataBaseName;
        java.sql.Connection connection = null;
        try {
            connection = DriverManager.getConnection(database, userName, password);
        } catch (SQLException e) {
            System.out.println("Error during connecting to database");
            System.exit(1);
        }
        return connection;
    }
    /**
     * Displays data from SELECT query
     *
     * @param r
     *            - result
     */
    private static void printDataFromQuery(ResultSet r) {
        ResultSetMetaData rsmd;
        try {
            rsmd = r.getMetaData();

            int numcols = rsmd.getColumnCount();

            // display names of columns:
            for (int i = 1; i <= numcols; i++) {
                System.out.print("\t" + rsmd.getColumnLabel(i) + "\t|");
            }
            System.out.print("\n____________________________________________________________________________\n");
            //r.next() - jump to next record
            while (r.next()) {
                for (int i = 1; i <= numcols; i++) {
                    Object obj = r.getObject(i);
                    if (obj != null)
                        System.out.print("\t" + obj.toString() + "\t|");
                    else
                        System.out.print("\t");
                }
                System.out.println();
            }
        } catch (SQLException e) {
            System.out.println("Error during reading from database" + e.toString());
            System.exit(3);
        }
    }

    /**
     * Wykonanie kwerendy i przesłanie wyników do obiektu ResultSet
     *
     * @param s
     *            - Statement
     * @param sql
     *            - zapytanie
     * @return wynik
     */
    private static ResultSet executeQuery(Statement s, String sql) {
        try {
            return s.executeQuery(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * tworzenie obiektu Statement przesyłającego zapytania do bazy connection
     *
     * @param connection
     *            - połączenie z bazą
     * @return obiekt Statement przesyłający zapytania do bazy
     */
    private static Statement createStatement(Connection connection) {
        try {
            return connection.createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        ;
        return null;
    }

    /**
     * Zamykanie połączenia z bazą danych
     *
     * @param connection
     *            - połączenie z bazą
     * @param s
     *            - obiekt przesyłający zapytanie do bazy
     */
    private static void closeConnection(Connection connection, Statement s) {
        System.out.print("\nZamykanie polaczenia z databaseą:");
        try {
            s.close();
            connection.close();
        } catch (SQLException e) {
            System.out
                    .println("Bląd przy zamykaniu polączenia " + e.toString());
            System.exit(4);
        }
        System.out.print(" zamknięcie OK");
    }

    public JDBC(){
        if (loadDriver())
            System.out.print("Driver correct");
        else
            System.exit(1);
        java.sql.Connection connection = connectToDatabase("127.0.0.1",
                "kuku", "root", "");
        if (connection != null)
            System.out.print("Connection correct\n");

        // WYKONYWANIE OPERACJI NA BAZIE DANYCH
        System.out.println("Pobieranie danych z bazy:");
        //String sql = "INSERT INTO Winnings (name, won) VALUES ('pawel', 2)";
        String sql = "Select * from Winnings";
        Statement s = createStatement(connection);
        ResultSet r = executeQuery(s, sql);
        printDataFromQuery(r);
        closeConnection(connection, s);
    }
}