Entity Relation as identity for self-referential relation breaks enhancer
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Key: OPENJPA-291
URL: https://issues.apache.org/jira/browse/OPENJPA-291
Project: OpenJPA
Issue Type: Bug
Reporter: Pinaki Poddar
Priority: Minor
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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