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https://issues.apache.org/jira/browse/OPENJPA-291?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12740601#action_12740601
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Krzysztof commented on OPENJPA-291:
-----------------------------------
Hello,
This is quite common scenario in our project. Any chance to have it fixed in a
foreseeable future? Quite surprised it has low priority..
Best regards
Chris
> Entity Relation as identity for self-referential relation breaks enhancer
> -------------------------------------------------------------------------
>
> Key: OPENJPA-291
> URL: https://issues.apache.org/jira/browse/OPENJPA-291
> Project: OpenJPA
> Issue Type: Bug
> Reporter: Pinaki Poddar
> Priority: Minor
> Attachments: Node.jad, Node.java, TestTree.java
>
>
> Use Case:
> A Node of a tree has a reference to parent node and a collection of child
> nodes.
> The complexity is how the node is identified. Instead of a simple primary
> identity,
> the node is using an identity that is composed of a primitive and its parent.
> OpenJPA allows parent (a uni-cardinarity relation) to be used as part of
> compound primary key.
> But the entire process of enhancement and metadata resolution do not fully
> cover when the
> relation is self-recursive.
> The use case of defining such a key however does not seem to be common.
> Anyway, consider Node of a tree defined for persistence as follows:
> @Entity
> @IdClass(Node.SelfId.class)
> public class Node {
> @Id
> private long id;
>
> @Id
> @ManyToOne private Node parent;
>
> @OneToMany(mappedBy="parent", cascade=CascadeType.ALL)
> private List<Node> children;
> public class SelfId {
> public long id;
> public SelfId parent;
> }
> 1. Enhancer breaks on Node.class
> Because metadata resolution goes to infinite recursive loop and a
> StackOverflow
> The codelines that breaks are in MetaDataRepository and the
> tentative patch shows why infinite recursion is happening by just stopping
> it.
> The impact of cutting it short is not clear/investigated.
>
> Index:
> openjpa-kernel/src/main/java/org/apache/openjpa/meta/MetaDataRepository.java
> ===================================================================
> ---
> openjpa-kernel/src/main/java/org/apache/openjpa/meta/MetaDataRepository.java
> (revision 558795)
> +++
> openjpa-kernel/src/main/java/org/apache/openjpa/meta/MetaDataRepository.java
> (working copy)
> @@ -552,11 +552,15 @@
> // resolve relation primary key fields for mapping dependencies
> FieldMetaData[] fmds = meta.getDeclaredFields();
> - for (int i = 0; i < fmds.length; i++)
> - if (fmds[i].isPrimaryKey())
> + for (int i = 0; i < fmds.length; i++) {
> + if (fmds[i].isPrimaryKey()) {
> + if (fmds[i].getObjectIdFieldType().
> + isAssignableFrom(meta.getDescribedType()))
> + continue;
> getMetaData(fmds[i].getDeclaredType(),
> meta.getEnvClassLoader(), false);
> -
> + }
> + }
> 2. This patch stops the recursion but does not solve the problem.
> The enhanced Node class fails to create a ApplicationId. For a simple test
> case such as (the test case is attached)
> public void testPersistTree() {
> OpenJPAEntityManager em = getEM();
> em.begin();
> Node root = new Node(1000L,null);
> createTree(root, new int[]{1,2,3}, 2);// 3-levels,
> fanout/node=2
> em.persist(root);
> em.commit();
> }
>
> <1.0.0-SNAPSHOT-SNAPSHOT nonfatal general error>
> org.apache.openjpa.persistence.PersistenceException:
> org.apache.openjpa.util.ObjectId
> at org.apache.openjpa.kernel.BrokerImpl.persist(BrokerImpl.java:2437)
> at org.apache.openjpa.kernel.BrokerImpl.persist(BrokerImpl.java:2333)
> at org.apache.openjpa.kernel.BrokerImpl.persistAll(BrokerImpl.java:2279)
> at
> org.apache.openjpa.kernel.SingleFieldManager.persist(SingleFieldManager.java:264)
> at
> org.apache.openjpa.kernel.StateManagerImpl.cascadePersist(StateManagerImpl.java:2741)
> at org.apache.openjpa.kernel.BrokerImpl.persist(BrokerImpl.java:2432)
> at org.apache.openjpa.kernel.BrokerImpl.persist(BrokerImpl.java:2251)
> at
> org.apache.openjpa.kernel.DelegatingBroker.persist(DelegatingBroker.java:1010)
> at
> org.apache.openjpa.persistence.EntityManagerImpl.persist(EntityManagerImpl.java:541)
> at tree.TestTree.testPersistTree(TestTree.java:22)
>
>
> Caused by: java.lang.ClassCastException: org.apache.openjpa.util.ObjectId
> at tree.Node.pcCopyKeyFieldsToObjectId(Node.java)
> at
> org.apache.openjpa.util.ApplicationIds.create(ApplicationIds.java:386)
> at org.apache.openjpa.kernel.BrokerImpl.persist(BrokerImpl.java:2405)
> ... 27 more
> 3. How does the enhanced Node class looks like?
> Firstly, Java decomiler (jad) itself is confused about the same method.
> $ jad classes\tree\Node.class
> Parsing classes\tree\Node.class...Parsing inner class
> classes\tree\Node$SelfId.class...Overwrite Node.jad [y/n/a/s] ? y
> Generating Node.jad
> Couldn't fully decompile method pcCopyKeyFieldsToObjectId
> The decompiled file is attached.
> 4. The enhanced code is generated in
> PCEnhancer.addExtractObjectIdFieldValueCode()
> But I found the debugging the piece hard.
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