DAO

package th.athichitsakul.dao;

import java.util.HashMap;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

public class DAO {
    private static final HashMap<String, EntityManagerFactory> factoryMAP = new HashMap<>();
    private EntityManagerFactory factory;
    private EntityManager entityManager;
    private EntityTransaction transaction;

    public DAO(String puID) {
        factory = factoryMAP.get(puID);
        if (factory == null) {
            factory = Persistence.createEntityManagerFactory(puID);
            factoryMAP.put(puID, factory);
        }

        entityManager = factory.createEntityManager();
    }
    public void begin() {
        if (!entityManager.isOpen()) {
            entityManager = factory.createEntityManager();
        }
        transaction = entityManager.getTransaction();
        transaction.begin();
    }
    public void close() {
        entityManager.close();
    }
    public EntityManager getEntityManager() {
        return entityManager;
    }
    public EntityTransaction getTransaction() {
        return transaction;
    }
    public void clear() {
        entityManager.clear();
    }
    public void save(Object entity) {
        entityManager.persist(entity);
        transaction.commit();
    }
}