com.royken.generic.dao.impl.GenericDao Maven / Gradle / Ivy

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A library that provides CRUD and find all methods with JPA
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package com.royken.generic.dao.impl;

import com.royken.generic.dao.DataAccessException;
import com.royken.generic.dao.IGenericDao;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

/**
 * @author KENFACK Valmy-Roi 
 * @param  
 * @param 
 */
public class GenericDao implements IGenericDao {
    private Class entityClass;
    @PersistenceContext
    private EntityManager manager;

    public GenericDao() {
        this.entityClass = (Class) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
    }

    public Class getEntityClass() {
        return this.entityClass;
    }

    public EntityManager getManager() throws DataAccessException {
        if (this.manager == null) {
            throw new DataAccessException("Le gestionnaire des entit\u00e9s n'est pas encore d\u00e9fini");
        }
        return this.manager;
    }

    public void setManager(EntityManager manager) throws DataAccessException {
        this.manager = manager;
    }

    public T create(T newInstance) throws DataAccessException{
        try {
             this.getManager().persist(newInstance);
        return newInstance;
        } catch (Exception e) {
        }
       return null;
    }

    public T findById(ID id) throws DataAccessException{
        try {
            return (T)this.getManager().find(this.entityClass, id);
        } catch (Exception e) {
        }
        return null;
    }

    public T update(T transientObject) throws DataAccessException{
        try {
            return (T)this.getManager().merge(transientObject);
        } catch (Exception e) {
        }
         return null;
    }

    public void delete(T persistentObject) throws DataAccessException{
        this.getManager().remove(persistentObject);
    }

    public List findAll() throws DataAccessException {
        return this.getManager().createQuery(" select u from " + this.entityClass.getName() + " u").getResultList();
    }

    public List findRange(int begin, int end) throws DataAccessException {
        return this.getManager().createQuery(" select u from " + this.entityClass.getName() + " u").setMaxResults(end - begin + 1).setFirstResult(begin).getResultList();
    }

    public Long count() throws DataAccessException {
        return  (Long)(this.getManager().createQuery(" select count(*) from " + this.entityClass.getName() ).getResultList().get(0));
      //  return ((Long) q.getSingleResult()).intValue();       
    }
}