javax.persistence.Query.getResultList() 可以返回 null 吗? [英] Can javax.persistence.Query.getResultList() return null?

问题描述

如果是，在什么情况下?

And if so, under what circumstances?

Javadoc 和 JPA 规范什么也没说.

Javadoc and JPA spec says nothing.

推荐答案

你说得对.JPA 规范对此一无所知.但是Java Persistence with Hibernate 一书，第 2 版说:

You are right. JPA specification says nothing about it. But Java Persistence with Hibernate book, 2nd edition, says:

如果查询结果为空，则返回null

If the query result is empty, a null is returned

当您调用 query.getResultList() 没有结果时，Hibernate JPA 实现(实体管理器)返回 null.

Hibernate JPA implementation (Entity Manager) return null when you call query.getResultList() with no result.

更新

正如一些用户所指出的，似乎最新版本的 Hibernate 返回一个空列表.

As pointed out by some users, it seems that a newest version of Hibernate returns an empty list instead.

如果未找到任何结果，Eclipselink 中也会返回一个空列表.

An empty list is returned in Eclipselink as well when no results are found.

这篇关于javax.persistence.Query.getResultList() 可以返回 null 吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！