GAE 数据存储中的 JPA 错误
我试图让我的 GAE 应用程序从数据存储区中提取一些记录，但不断收到此信息：
javax.persistence.PersistenceException: Class PersistableItem for query has not been resolved. Check the query and any imports specification
它来自此处的方法：
public List<PersistableItem> listItems() {
EntityManager em = EMFService.get().createEntityManager();
// Read the existing entries
Query q = em.createQuery("select * from PersistableItem");
List<PersistableItem> items = q.getResultList();
return items;
}
从我读到的内容来看，这是关于导入我的 PersistableItem 类，但我很困惑，因为我已经在.java 代码文件。
I'm trying to have my GAE app pull some records from the Datastore but keep getting this:
javax.persistence.PersistenceException: Class PersistableItem for query has not been resolved. Check the query and any imports specification
It's from the method here:
public List<PersistableItem> listItems() {
EntityManager em = EMFService.get().createEntityManager();
// Read the existing entries
Query q = em.createQuery("select * from PersistableItem");
List<PersistableItem> items = q.getResultList();
return items;
}
From what I've read this is about importing my PersistableItem class but I'm confused as I already do that in the .java code files.
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评论（3）
错误消息很奇怪，所以这可能不是您唯一的错误，但您的查询是错误的。 select * 是 SQL，而不是 JPQL。正确的查询是
The error message is strange, so this might not be your only error, but your query is wrong. select * is SQL, not JPQL. The correct query is
您的项目中（或项目的依赖项中）是否存在“PersistableItem”类。它是否具有
@Entity类级别注释。它是否实现了可序列化。在 JPQL 中尝试使用类的完全限定名称（“select * from package1.package2.PersistableItem”）Is the class "PersistableItem" present in your project (or in a dependency of your project). Does it have the
@Entityclass level annotation. Does it implement Serializable. In your JPQL try using the fully qualified name of the class ("select * from package1.package2.PersistableItem")即使使用正确的 JPQL 查询，我也遇到了同样的错误，并解决了在 persistence.xml 中添加类声明的问题
I had the same error even with the right JPQL query and solved adding the class declarations in the persistence.xml