5 ways to initialize lazy relations and when to use them (http://www.thoughts-on-java.org/2014/12/5-ways-to-initialize-lazy-relations.html)

defineNamedGraph.java

@Entity
@NamedEntityGraph(name = "graph.Order.items", 
      attributeNodes = @NamedAttributeNode("items"))
public class Order implements Serializable {
....

dynamicGraph.java

EntityGraph graph = this.em.createEntityGraph(Order.class);
Subgraph itemGraph = graph.addSubgraph("items");
    
Map hints = new HashMap();
hints.put("javax.persistence.loadgraph", graph);
  
Order order = this.em.find(Order.class, orderId, hints);

fetchJoinCriteria.java

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery q = cb.createQuery(Order.class);
Root o = q.from(Order.class);
o.fetch("items", JoinType.INNER);
q.select(o);
q.where(cb.equal(o.get("id"), orderId));

Order order = (Order)this.em.createQuery(q).getSingleResult();

fetchJoinJPQL.java

Query q = this.em.createQuery("SELECT o FROM Order o JOIN FETCH o.items i WHERE o.id = :id");
q.setParameter("id", orderId);
newOrder = (Order) q.getSingleResult();

mappedRelation.java

Order order = this.em.find(Order.class, orderId);
order.getItems().size();

useNamedGraph.java

EntityGraph graph = this.em.getEntityGraph("graph.Order.items");
  
Map hints = new HashMap();
hints.put("javax.persistence.fetchgraph", graph);
  
Order order = this.em.find(Order.class, orderId, hints);