[OPENJPA-562] NPE when trying to invoke FieldMetada.getOrders() when a PersistenCollection field is being loaded.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.0
• Fix Version/s: 1.1.0
• Component/s: kernel
• Environment: This error occured on Microsoft Windows XP SP2, Java version = 1.6.0 with mySQL 5.0 Database.
• Assignee: Unassigned
• Reporter: Sandeep Shrivastava
• Created: 08/Apr/08 21:35
• Updated: 09/Mar/10 18:32
• Resolved: 08/Apr/08 22:36

Description

Consider the following snippet of an entity definition:

/**

• <p>Entity used to test parsing of @OrderBy.</p>
  *
• @author Abe White
  */
  @Entity
  public class OrderByEntity { @Id private long id; private String string; @PersistentCollection @OrderBy private List<String> strings = new ArrayList(); }

The @PersistentCollection annotation maps the declaration to the default collection table named orderbyentity_strings. The join column name in the container table is also defaulted to orderbyentity_id and the name of the Element column name is defaulted to element.

The test code initially added string elements to the strings list and persisted it.

OrderByEntity pc = new OrderByEntity();
pc.setId(1L);
pc.getStrings().add("2");
pc.getStrings().add("1");
pc.getStrings().add("3");

On a subsequent load of the persistent collection data by executing the following code, we hit into an NPE.

pc = em.find(OrderByEntity.class, 1L);
List<String> strings = pc.getStrings();

java.lang.NullPointerException
at org.apache.openjpa.meta.FieldMetaData.getOrders(FieldMetaData.java:1127)
at org.apache.openjpa.jdbc.meta.strats.StoreCollectionFieldStrategy.selectEager(StoreCollectionFieldStrategy.java:207)
at org.apache.openjpa.jdbc.meta.strats.StoreCollectionFieldStrategy.selectEagerJoin(StoreCollectionFieldStrategy.java:171)
at org.apache.openjpa.jdbc.meta.FieldMapping.selectEagerJoin(FieldMapping.java:713)
at org.apache.openjpa.jdbc.kernel.JDBCStoreManager.select(JDBCStoreManager.java:927)
at org.apache.openjpa.jdbc.kernel.JDBCStoreManager.load(JDBCStoreManager.java:503)
at org.apache.openjpa.kernel.DelegatingStoreManager.load(DelegatingStoreManager.java:116)
at org.apache.openjpa.datacache.DataCacheStoreManager.load(DataCacheStoreManager.java:368)
at org.apache.openjpa.kernel.DelegatingStoreManager.load(DelegatingStoreManager.java:116)
at org.apache.openjpa.kernel.ROPStoreManager.load(ROPStoreManager.java:78)
at org.apache.openjpa.kernel.StateManagerImpl.loadFields(StateManagerImpl.java:2911)
at org.apache.openjpa.kernel.StateManagerImpl.loadField(StateManagerImpl.java:2989)
at kodo.kernel.ProfilingStateManager.loadField(ProfilingStateManager.java:68)
at org.apache.openjpa.kernel.StateManagerImpl.beforeAccessField(StateManagerImpl.java:1489)
at kodo.kernel.ProfilingStateManager.beforeAccessField(ProfilingStateManager.java:49)
at org.apache.openjpa.kernel.StateManagerImpl.accessingField(StateManagerImpl.java:1474)

This problem is reported with OpenJPA version:

$ java org.apache.openjpa.conf.OpenJPAVersion
OpenJPA 1.1.0-SNAPSHOT
version id: openjpa-1.1.0-SNAPSHOT-r420667:634150
Apache svn revision: 420667:634150

os.name: Windows XP
os.version: 5.1
os.arch: x86

java.version: 1.6.0_05
java.vendor: BEA Systems, Inc.

The NPE occurs when the FieldMetadata.getOrders() method is invoked when trying to load the data in the strings collection field. The code is trying to get the ClassMetadata for the element type and then check the FieldMetadata is present in the declared fields. It fails because the element data type is java.lang.String and there is no ClassMetadata for it. By simply adding a null check for the returned class metadata this issue I could fix locally.

Here is the outout of the svn diff command.

C:\apache_openjpa_project\openjpa>svn diff
Index: openjpa-kernel/src/main/java/org/apache/openjpa/meta/FieldMetaData.java
===================================================================
— openjpa-kernel/src/main/java/org/apache/openjpa/meta/FieldMetaData.java
(revision 643944)
+++ openjpa-kernel/src/main/java/org/apache/openjpa/meta/FieldMetaData.java
(working copy)
@@ -1124,9 +1124,11 @@
//set "isUsedInOrderBy" to the field
ClassMetaData elemCls = getElement()
.getDeclaredTypeMetaData();

• FieldMetaData fmd = elemCls.getDeclaredField(decs[i]);
• if (fmd != null)
• fmd.setUsedInOrderBy(true);
  + if (elemCls != null) { + FieldMetaData fmd = elemCls.getDeclaredField(decs[i]); + if (fmd != null) + fmd.setUsedInOrderBy(true); + }

  }
  _orders = orders;
  }