@EJB injects EJBs only, but @Inject can be used to inject POJOs rather than EJBs. However, @Inject requires that your archive be a BDA (contain beans.xml for EE 6, or implicitly in EE 7). @Inject also has additional CDI-specific capabilities (scopes, interceptors, etc.), but those capabilities incur extra overhead. Application servers have support for specifying … Read more
This is a configuration I am using which keeps resources to a minimum. Of course you’ll want to tailor your application to use the resources it needs… Reference: http://www.mchange.com/projects/c3p0/index.html testConnectionOnCheckin validates the connection when it is returned to the pool. testConnectionOnCheckOut, although would ensure active connections before use, would be too expensive to do. idleConnectionTestPeriod … Read more
You can use a plugin like Eclipse Dali to do the trick for you. You can refer to the documentation, section 3.11 Generating Entities from Tables. I do not know of any specific vendor independent tool to do this, though.
You can do something like @NamedQuery(name=”findWhatever”, query=”SELECT new path.to.dto.MyDto(e.id, e.otherProperty) FROM Student e WHERE e.id = ?1″) Then the MyDto object would just need a constructor defined with the correct fields i.e. public MyDto(String id, String otherProperty) { this.id = id; this.otherProperty = otherProperty; }
Below is the pseudo-code for using sub-query using Criteria API. CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder(); CriteriaQuery<Object> criteriaQuery = criteriaBuilder.createQuery(); Root<EMPLOYEE> from = criteriaQuery.from(EMPLOYEE.class); Path<Object> path = from.get(“compare_field”); // field to map with sub-query from.fetch(“name”); from.fetch(“id”); CriteriaQuery<Object> select = criteriaQuery.select(from); Subquery<PROJECT> subquery = criteriaQuery.subquery(PROJECT.class); Root fromProject = subquery.from(PROJECT.class); subquery.select(fromProject.get(“requiredColumnName”)); // field to map with main-query subquery.where(criteriaBuilder.and(criteriaBuilder.equal(“name”,name_value),criteriaBuilder.equal(“id”,id_value))); select.where(criteriaBuilder.in(path).value(subquery)); … Read more
Both answers from Eric Lucio and Renan helped, but their use of the ids in the association table is redundant. You have both the associated entities and their ids in the class. This is not required. You can simply map the associated entity in the association class with the @Id on the associated entity field. … Read more
Specification says that derived entity should be the owning side of the relationship: 2.4.1 Primary Keys Corresponding to Derived Identities The identity of an entity may be derived from the identity of another entity (the “parent” entity) when the former entity (the “dependent” entity) is the owner of a many-to-one or one-to-one relationship to the … Read more
This warning means nothing, you shouldn’t worry about it since you don’t need to apply any post-processors to the DataSource. Technically it means that some bean post-processor (a transactional one, I guess) depends on your DataSource, therefore the DataSource must be fully initialized before initialization of that post-processor, so that the post-processor cannot intercept initialization … Read more
If I’m using an ORM like JPA2 – where I have my entities that are mapped to my database, should I still be using a DAO? It seems like a lot more overhead. It is. And clearly, Java EE doesn’t encourage using the DAO pattern when using JPA (JPA already provides a standardized implementation of … Read more
It is possible starting from the version 2.1 of JPA using the on method Join<Z, X> on(Predicate… restrictions); Here is how: Root<Order> order = cq.from(Order.class); Join<Order, Item> item = order.join(Order_.itemList, JoinType.LEFT); item.on(cb.equal(item.get(Item_.type), 1));