在@Query批注中指定查询时，如何使用Spring Data JPA初始化惰性关联? [英] How can I initialize lazy associations using Spring Data JPA when the query is specified in @Query annotation?

问题描述

这是我的查询之前，我转换为Spring Data JPA.请注意，我以前是如何使用Hibernate.initialize()手动获取窗口小部件的消息的.

Here's my query before I converted over to Spring Data JPA. Notice how I used to use Hibernate.initialize() to manually fetch the widget's messages.

public Object findWidget(final Widget findMe) {
    Widget widget = getJpaTemplate().execute(new JpaCallback<Widget>() {
        public Widget doInJpa(EntityManager em) throws PersistenceException {
            Query q = em.createQuery("SELECT h FROM " + entityClass.getName() + " h where h.widgetId = ? ");
            q.setParameter(1, findMe.getId());

            Widget found = (Widget)q.getSingleResult();

            //Initialize lazy associations
            if(found!= null){
                Hibernate.initialize(widget.getMessages());
            }

            return found;
        }
    });
    return widget;
}

这是我的查询功能现在的样子.请注意，没有正文可以放入Hibernate.initialize().

And here's what my query function looks like now. Notice there is no body to put the Hibernate.initialize() in.

@Query("SELECT h FROM Widget h where h.widgetId = ?1 ")
public AccessPoint findWidget(String widgetId);

那么我如何指定要主动而不是懒惰地获取小部件的消息?

So how can I specify that the widget's messages are to be fetched actively and not lazily?

推荐答案

尝试获取联接，如下所示:

Try a fetch join, something like this:

@Query("SELECT h FROM Widget h LEFT JOIN FETCH h.messages WHERE h.widgetId = ?1 ")
public AccessPoint findWidget(String widgetId);

http://docs.oracle.com/html/E24396_01/ejb3_langref. html#ejb3_langref_fetch_joins

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