Use some JPA 2 implementation: it adds a @ElementCollection annotation, similar to the Hibernate one, that does exactly what you need. There’s one example here. Edit As mentioned in the comments below, the correct JPA 2 implementation is javax.persistence.ElementCollection @ElementCollection Map<Key, Value> collection; See: http://docs.oracle.com/javaee/6/api/javax/persistence/ElementCollection.html
MappedBy signals hibernate that the key for the relationship is on the other side. This means that although you link 2 tables together, only 1 of those tables has a foreign key constraint to the other one. MappedBy allows you to still link from the table not containing the constraint to the other table.
For versions earlier than JPA 2.1, JPA provides only two ways to deal with enums, by their name or by their ordinal. And the standard JPA doesn’t support custom types. So: If you want to do custom type conversions, you’ll have to use a provider extension (with Hibernate UserType, EclipseLink Converter, etc). (the second solution). … Read more
orphanRemoval has nothing to do with ON DELETE CASCADE. orphanRemoval is an entirely ORM-specific thing. It marks “child” entity to be removed when it’s no longer referenced from the “parent” entity, e.g. when you remove the child entity from the corresponding collection of the parent entity. ON DELETE CASCADE is a database-specific thing, it deletes … Read more
JPA will use all properties of the class, unless you specifically mark them with @Transient: @Transient private String agencyName; The @Column annotation is purely optional, and is there to let you override the auto-generated column name. Furthermore, the length attribute of @Column is only used when auto-generating table definitions, it has no effect on the … Read more
You can use projections from Spring Data JPA (doc). In your case, create interface: interface ProjectIdAndName{ String getId(); String getName(); } and add following method to your repository List<ProjectIdAndName> findAll();
I have found a couple of solutions to this. Using Mapped Entities (JPA 2.0) Using JPA 2.0 it is not possible to map a native query to a POJO, it can only be done with an entity. For instance: Query query = em.createNativeQuery(“SELECT name,age FROM jedi_table”, Jedi.class); @SuppressWarnings(“unchecked”) List<Jedi> items = (List<Jedi>) query.getResultList(); But in … Read more
To map a composite key, you can use the EmbeddedId or the IdClass annotations. I know this question is not strictly about JPA but the rules defined by the specification also applies. So here they are: 2.1.4 Primary Keys and Entity Identity … A composite primary key must correspond to either a single persistent field … Read more
The OSIV Anti-Pattern Instead of letting the business layer decide how it’s best to fetch all the associations that are needed by the View layer, OSIV (Open Session in View) forces the Persistence Context to stay open so that the View layer can trigger the Proxy initialization, as illustrated by the following diagram. The OpenSessionInViewFilter … Read more