criteriaquery

I love the type safety CriteriaQuery brings ing JPA 2.0 but it also brings a bit of boiler-plate code. For example, let say I have an entity called NamedEntity, which simply has an id and a String field called "name" (assume it has the unique constraint set to true). Here's what the NamedEntityManager might look like: public class NamedEntityManager { //inject using your framework EntityManager entityManager; //retrieve all existing entities of type NamedEntity from DB public Iterable<NamedEntity> queryAll() { CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery

I have the following EJB structure. Don't wonder about Animal and Inventory , these classes are only here to demonstrate the structure in a simplified way ( Update : I have revised the class names to construct a better understandable example. Another implementation of IdTag might be a BarcodeId ). Note that there is no inverse relationship from IdTag to Animal or Inventory , and let's assume the RfidTag.code is unique. I read Retrieving Polymorphic Hibernate Objects Using a Criteria Query and Hibernate polymorphic query but these discussions does not seem to answer my question. public

I’m using JPA 2.0 with Hibernate 4.1.0.Final. I have a couple of classes, Groups and GroupMembers. Each GroupMember is tied to a user object @Entity @Table(name = "group") public class Group { @Id @NotNull @GeneratedValue(generator = "uuid-strategy") @Column(name = "ID") private String id; … @OneToMany(mappedBy = "group") private Set<GroupMember> members; @Entity @Table(name = "sb_msg_group_member") public class GroupMember { … @ManyToOne @JoinColumn(name = "USER_ID", nullable = false, updatable = true) private User user; Is it possible to write a JPA criteria query that given a java.util.Set

Consider the following: @Entity public class Book { private List<String> authors; @ElementCollection public List<String> getAuthors() { return authors; } public void setAuthors(List<String> authors) { this.authors = authors; } } How to type a JPA2 CriteriaQuery expression which, say, will let me find all the Books which have more than 2 authors? JB Nizet In JPQL: select b from Book where size(b.authors) >= 2 Using the criteria API (but why would you replace such a simple static query with the following mess?): CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<Book> criteriaQuery = cb

I am rather new to JPA 2 and it's CriteriaBuilder / CriteriaQuery API: CriteriaQuery javadoc CriteriaQuery in the Java EE 6 tutorial I would like to count the results of a CriteriaQuery without actually retrieving them. Is that possible, I did not find any such method, the only way would be to do this: CriteriaBuilder cb = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> cq = cb .createQuery(MyEntityclass); // initialize predicates here return entityManager.createQuery(cq).getResultList().size(); And that can't be the proper way to do it... Is there a solution? Affe A query of type

Is it possible to select, say, only properties A and B from an object using a JPA query without using criteria queries? To select all properties I'd just do something like: SELECT i FROM ObjectName i WHERE i.id = 10 But I have an object with many properties on a legacy system, and want to select just a few even though I'm aware selecting several properties is usually quick. Is this possible without using criteria queries? Thank you! Yes, like in plain sql you could specify what kind of properties you want to select: SELECT i.firstProperty, i.secondProperty FROM ObjectName i WHERE i.id=10