使用Criteria API进行动态JPA 2.0查询

Question

I am a bit stucked constructing a dynamic query using the CriteriaBuilder of JPA 2.0.

I have quite a common use case I guess: User supplies a arbitrary amount of search parameters X to be and / or concatenated: like :

select e from Foo where (name = X1 or name = X2 .. or name = Xn )

The Method or of CriteriaBuilder is not dynamic:

Predicate or(Predicate... restrictions)

Ideas? Samples?

Answer 1

In your case, I would rather use Expression#in(Collection) to avoid having to loop and to build a compound Predicate dynamically:

CriteriaBuilder cb = em.getCriteriaBuilder();

CriteriaQuery<Foo> cq = cb.createQuery(Foo.class);
Metamodel m = em.getMetamodel();
EntityType<Foo> Foo_ = m.entity(Foo.class);
Root<Foo> foo = cq.from(Foo_);
cq.where(my.get(Foo_.name).in(params));

You might want to check Basic Type-Safe Queries Using the Criteria API and Metamodel API for more details.

Answer 2

in this code Foo_.name is going to give compilation error. As the field is not declared in that. I'm not able to understand this. Please suggest me.

-raghu