A Generic DAO for Hibernate and JPA

This is just a little tip, nothing earth-shattering. ;-) On a few projects I've seen a DAO written or generated for every entity. Most of these DAOs only contained the methods for CRUD operations (Create, Update, Delete) on that entity. That meant a lot of needless repetition. With generics, introduced in Java 5, we can build a type-safe generic DAO that does the job of those generated objects.

public class GenericDAO<E extends Object>{

 private Class entityClass;

 

 protected GenericDAO(Class entityClass) {

 this.entityClass = entityClass;

 }



 public E get(Serializable id) {

 return (E) getSesion().get(entityClass, id);

 }

 

 public void save(E entity) {

 getSesion().save(entity);

 }

 

 public void update(E entity) {

 getSesion().save(entity);

 }

 

 public void delete(E entity) {

 getSesion().delete(entity);

 }

 

 protected Session getSesion() {

 return null; //get Hibernate session from somewhere

 }

 

 protected Class getEntityClass() {

 return entityClass;

 }

 

 public static <T extends Object> GenericDAO createGenericDAO(Class clazz) {

 GenericDAO dao = new GenericDAO(clazz); 

 return dao;

 }

}

Once it's set up, the DAO is easy to use in your code.

GenericDAO dao = GenericDAO.createGenericDAO(Dog.class);

Dog dog = dao.get(1);