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JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1734453]

Wed, 08 June 2016 09:21

Eclipse User

I use EclipseLink 2.6.3 as a JPA provider. I have the following code:

String queryString="SELECT a FROM Student a WHERE a.id='"+id+"'";
EntityGraph<Student> eg = em.createEntityGraph(Student.class);
eg.addAttributeNodes("id");
Query query = em.createQuery(queryString);
query.setHint("javax.persistence.fetchgraph", eg);
List<Student> items=query.getResultList();

However, I get exception:

    org.eclipse.persistence.exceptions.QueryException: Exception Description: You must define a fetch group manager at descriptor (com.temp.Student) in order to set a fetch group on the query (null) Query: ReadObjectQuery(referenceClass=Student jpql="SELECT a FROM Student a WHERE a.id='1'") FetchGroup(null){id}

In internet people say that it is necessary to enable weaving, so I added

<property name="eclipselink.weaving" value="true"/>

to my persistence.xml. However, it didn't help. Besides is not clear, why it complains about fetch group while I use fetch graph.

P.S. As I found here http://www.radcortez.com/jpa-entity-graphs/

Before JPA 2.1, the implementations already supported a non standard
way to load data similar to Entity Graphs. You have Hibernate Fetch
Profiles, OpenJPA Fetch Groups and EclipseLink Fetch Groups. It was
logical to have this kind of behaviour in the specification. It allows
you a much finer and detail control on what you need to load using a
standard API.

So maybe eclipselink implements entity graph using fetchgroup. But anyway it is not clear how to fix this problem.

The question moved to Gemini Jpa https://www.eclipse.org/forums/index.php/t/1078217/

[Updated on: Wed, 08 June 2016 11:43] by Moderator

Re: JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1734847 is a reply to message #1734453]

Mon, 13 June 2016 09:39

Eclipse User

You should fix your weaving issues first, as they are required to get entity graph functionality built into your Entities. The "eclipselink.weaving" property tells EclipseLink that an agent should be involved to weave the classes - you still need to either manually add the agent to your JVM, or be using a container that supports JPA weaving. See http://www.eclipse.org/eclipselink/documentation/2.5/concepts/app_dev007.htm

Re: JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1734853 is a reply to message #1734847]

Mon, 13 June 2016 09:55

Eclipse User

I don't understand you. I use dynamic weaving. As I understand, in order to do it I must only write in persistence.xml

<property name="eclipselink.weaving" value="true"/>

If not, what else should I do? I use EclipseLink in JavaSE

P.S. I asked this question on SO - http://stackoverflow.com/questions/37746308/jpa-entitygraph-and-map

[Updated on: Mon, 13 June 2016 09:58] by Moderator

Re: JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1734884 is a reply to message #1734453]

Mon, 13 June 2016 09:39

Eclipse User

Re: JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1734891 is a reply to message #1734453]

Mon, 13 June 2016 09:39

Eclipse User

Re: JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1734976 is a reply to message #1734891]

Tue, 14 June 2016 06:54

Eclipse User

Forum seems to duplicate posts. So I ask you again - please, explain what else should I do to enable dynamic weaving besides <property name="eclipselink.weaving" value="true"/> in config.

Re: JPA: EntityGraph -> FetchGroupException [CLOSED] [message #1735625 is a reply to message #1734976]

Tue, 21 June 2016 09:23

Eclipse User

https://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Advanced_JPA_Development/Performance/Weaving/Dynamic_Weaving

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