使用JPQL示例的Entity类中的动态命名查询

问题描述

我有一个命名查询如下;

I have a named query as below;

@NamedQuery(name = "MyEntityClass.findSomething", query = "SELECT item FROM MyTable mytbl")

现在我想在此查询中附加动态排序子句（基于UI）参数）

Now I want to append dynamic sort clause to this query (based on UI parameters)

我可以使用JPQL做一个相同的例子（比如如何在Entity类中设置动态ORDER BY）

Can I get an example using JPQL for doing the same (like how to set a dynamic ORDER BY in the Entity class)

我已经尝试过使用CriteriaQuery，但现在正在寻找JPQL实现。

I have already tried using CriteriaQuery, but was looking for a JPQL implementation now.

推荐答案

NamedQueries是根据定义，不是动态的，以编程方式更改它们是不正确的。

NamedQueries are by definition NOT dynamic, it is not correct to change them programmatically.

所以要做的就是创建一个JPQL查询（但不是命名查询），如下所示：

So the way to go is to create a JPQL query (but not a named query) like this:

TypedQuery<MyEntity> query = em.createdQuery("SELECT item FROM MyEntity item ORDER BY "+sortingCol, MyEntity.class);

另一方面，如果你真的想要使用命名查询，你可以这样做以下方式：

On the other hand, if you REALLY want to use the named query, you could do that the following way:

@NamedQuery(name = "MyEntityClass.findSomething", query = MyEntity.NAMED_QUERY)
@Entity
public class MyEntity {
    public static final NAMED_QUERY= "SELECT item FROM MyTable mytbl";
    //+your persistent fields/properties...
}
//and later in your code
TypedQuery<MyEntity> query = entityManager.createQuery(MyEntity.NAMED_QUERY + " ORDER BY " + sortingCol, MyEntity.class);

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