这是一个示例界面：
public interface GenericDao<T, PK extends Serializable> { T create(T t); T read(PK id); T update(T t); void delete(T t);}和一个实现：
public class GenericDaoJpaImpl<T, PK extends Serializable> implements GenericDao<T, PK> { protected Class<T> entityClass; @PersistenceContext protected EntityManager entityManager; public GenericDaoJpaImpl() { ParameterizedType genericSuperclass = (ParameterizedType) getClass() .getGenericSuperclass(); this.entityClass = (Class<T>) genericSuperclass .getActualTypeArguments()[0]; } @Override public T create(T t) { this.entityManager.persist(t); return t; } @Override public T read(PK id) { return this.entityManager.find(entityClass, id); } @Override public T update(T t) { return this.entityManager.merge(t); } @Override public void delete(T t) { t = this.entityManager.merge(t); this.entityManager.remove(t); }}
