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From "Willis Blackburn (JIRA)" <j...@apache.org>
Subject [jira] Commented: (OPENJPA-1804) NPE in MappingInfo.java line 1514
Date Tue, 21 Sep 2010 11:13:38 GMT

    [ https://issues.apache.org/jira/browse/OPENJPA-1804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12912936#action_12912936
] 

Willis Blackburn commented on OPENJPA-1804:
-------------------------------------------

When I don't have RuntimeEnhancedClasses set, I get:

Internal error: This configuration disallows runtime optimization, but the following listed
types were not enhanced at build time or at class load time with a javaagent: (all my classes)

When I set RuntimeEnhancedClasses=supported, the app works (now that I've gotten rid of all
the mapping problems).  However I do NOT see the info message "OpenJPA dynamically loaded
the class enhancer" mentioned in the documentation.  I'm logging at the debug level.

But there is this message:  "Creating subclass for '[class com.signetworks.signs.model.security.Group,
class com.signetworks.signs.model.addressbook.AddressBook, class com.signetworks.signs.model.addressbook.PhoneNumber,
class com.signetworks.signs.model.addressbook.SnailAddress, class com.signetworks.signs.model.security.User,
class com.signetworks.signs.model.addressbook.EmailAddress, class com.signetworks.signs.model.entities.HostName,
class com.signetworks.signs.model.security.Organization]'. This means that your application
will be less efficient and will consume more memory than it would if you ran the OpenJPA enhancer.
Additionally, lazy loading will not be available for one-to-one and many-to-one persistent
attributes in types using field access; they will be loaded eagerly instead."

Oops!

I traced through the InstrumentationFactory class.  Looks like the Java 6 attach API enhancer
is not being loaded because my application is not being loaded by the system class loader.
 One for the documentation!

Also, I think that even if the system class loader check had passed, the agent installation
would have failed because the OS X JVM doesn't have a tools.jar.  Instead the attach API classes
are in "classes.jar."

> NPE in MappingInfo.java line 1514
> ---------------------------------
>
>                 Key: OPENJPA-1804
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-1804
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: Enhance, UnenhancedClasses, usability
>    Affects Versions: 2.0.1
>            Reporter: Willis Blackburn
>
> I am encountering a NPE at MappingInfo.java line 1514.  I'm sorry I don't have time to
prepare a test case right now.  I'm not even 100% sure what is causing the problem, but it
seems to be something like this:
> I have classes Organization, Group, User, and AddressBook.
> Group has a reference (many-to-one) to Organization.
> I'm using field-level access and the Java 6 runtime enhancer.  (NOT the build-time enhancer
or the agent.)
> In ManagedClassSubclasser.prepareUnenhancedClasses, the code receives a list of Class
objects--the ones in persistence.xml.  They are not in the same order as they are in persistence.xml,
but I don't know if that's important.  The first one is Group.  During the processing of Group,
the code invokes ClassMapping.setTable to set the table name, which is "group_table."  This
comes from the @Table annotation of Group.  So far, so good.  Then the code does some additional
processing on the relationship mappings of Group, which include the reference to Organization.
 During the processing of that relationship, the code calls MappingInfo.mergeJoinColumn. 
On line 1367, the method calls rel.getTable.  The "rel" variable points to the ClassMapping
for Organization.  Remember that prepareUnenhancedClasses hasn't gotten to Organization yet--it's
still working on Group--and so I assume that this Organization mapping was created on-demand.
 However, rel.getTable returns null.  The Organization class has a @Table attribute, and I
can see that the table name has been loaded in the ClassMappingInfo instance attached to the
ClassMapping for Organization, however the table name has not yet been copied from ClassMappingInfo
to ClassMapping.  Later, the mergeJoinColumn method attempts to dereference the null table
name and generates the NPE.
> Bottom line:  When using the Java 6, runtime enhancer, if class A has a reference to
class B, and both classes have @Table annotations (at least), and class A is processed first,
then it produces a NPE.

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