不确定您在谈论什么博客条目:) 但是在您的特定情况1中,我可能会使用单个会话 bean 来实现类似于以下内容的接口:
public interface GenericCrudService {
public <T> T create(T t);
public <T> T find(Class<T> type, Object id);
public <T> void delete(T t);
public <T> T update(T t);
public List findWithNamedQuery(String queryName);
public List findWithNamedQuery(String queryName, int resultLimit);
public List findWithNamedQuery(String namedQueryName,
Map<String, Object> parameters);
public List findWithNamedQuery(String namedQueryName,
Map<String, Object> parameters,
int resultLimit);
public <T> List<T> findWithNativeQuery(String sql, Class<T> type);
}
豆子如下:
@Stateless
@Remote(GenericCrudService.class)
@TransactionAttribute(TransactionAttributeType.MANDATORY)
public class GenericCrudServiceBean implements GenericCrudService {
@PersistenceContext
private EntityManager em;
@Override
public <T> T create(T t) {
em.persist(t);
return t;
}
@Override
public <T> T find(Class<T> type, Object id) {
return em.find(type, id);
}
@Override
public <T> void delete(T t) {
t = em.merge(t);
em.remove(t);
}
@Override
public <T> T update(T t) {
return em.merge(t);
}
@Override
public List findWithNamedQuery(String queryName) {
return em.createNamedQuery(queryName).getResultList();
}
@Override
public List findWithNamedQuery(String queryName, int resultLimit) {
return em.createNamedQuery(queryName).setMaxResults(resultLimit)
.getResultList();
}
@Override
public List findWithNamedQuery(String namedQueryName,
Map<String, Object> parameters) {
return findWithNamedQuery(namedQueryName, parameters, 0);
}
@Override
public List findWithNamedQuery(String namedQueryName,
Map<String, Object> parameters,
int resultLimit) {
Query query = this.em.createNamedQuery(namedQueryName);
if(resultLimit > 0) {
query.setMaxResults(resultLimit);
}
for (Map.Entry<String, Object> entry : parameters.entrySet()) {
query.setParameter(entry.getKey(), entry.getValue());
}
return query.getResultList();
}
@Override
@SuppressWarnings("unchecked")
public <T> List<T> findWithNativeQuery(String sql, Class<T> type) {
return em.createNativeQuery(sql, type).getResultList();
}
}
也可以看看
1大多数应用程序不应将原始 CRUD 直接暴露给客户端,而是将 CRUD 隐藏在实现业务规则的服务和封装对域存储 (the EntityManager
) 的访问之后。