SHiNE-server/SHiNE-server/shine-server-db/src/main/java/shine/db/DbController.java

package shine.db;

import shine.db.connection.DbProvider;
import shine.db.dao.DmDialogStateDAO;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * Нейтральная точка входа в runtime БД сервера.
 *
 * Runtime-сервер теперь поддерживает только PostgreSQL.
 */
public final class DbController implements DbProvider {

    private static volatile DbController instance;

    private final PostgresDbController delegate;
    private volatile boolean dmDialogStateBootstrapped;

    private DbController() {
        this.delegate = PostgresDbController.getInstance();
    }

    public static DbController getInstance() {
        if (instance == null) {
            synchronized (DbController.class) {
                if (instance == null) {
                    DbController created = new DbController();
                    instance = created;
                    created.bootstrapDmDialogStateIfNeeded();
                }
            }
        }
        return instance;
    }

    @Override
    public Connection getConnection() throws SQLException {
        return delegate.getConnection();
    }

    @Override
    public void close() {
        delegate.close();
    }

    private void bootstrapDmDialogStateIfNeeded() {
        if (dmDialogStateBootstrapped) return;
        synchronized (this) {
            if (dmDialogStateBootstrapped) return;
            try (Connection connection = delegate.getConnection()) {
                DmDialogStateDAO.getInstance().bootstrapIfEmpty(connection);
                dmDialogStateBootstrapped = true;
            } catch (SQLException e) {
                instance = null;
                throw new RuntimeException("DM dialog state bootstrap failed", e);
            }
        }
    }
}