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Configuration of persistence.xml while using websphere 8.5.5.1

I'm coding an app that uses Servlet 3.0, Jsp, and JPA 2.0 and i'm deploying it into Websphere application server 8.5.
Since i already configured into the ibm websphere console, the data source and the jdbc driver, and the j2c authentification (i'm using oracle 11g as a database ). I dont know how my persistence.xml should look like, if i need to specify and add openJPA jars to my project.
For now anything i put into persistence.xml i'm having this issue :
Error 500: <openjpa-2.2.3-SNAPSHOT-r422266:1764177 fatal user error> org.apache.openjpa.persistence.ArgumentException
What should i do ? maybe i'm missing how JPA works
Thanks in advance

The OpenJPA jars should be provided by WebSphere and available to use for your application. There is a JPA sample available here: https://developer.ibm.com/wasdev/downloads/#asset/samples-Java_Persistence_API_JPA_Sample
In the sample, you can see an example of the persistence.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="jpasamplepersistenceunit">
<jta-data-source>java:comp/env/jdbc/samplejpadatasource</jta-data-source>
<non-jta-data-source>java:comp/env/jdbc/samplejpadatasourcenonjta</non-jta-data-source>
<class>wasdev.sample.jpa.Thing</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<!-- These properties are creating the database on the fly. We are using them to avoid users having
to create a database to run the sample.
See also the create=true line in the datasource meta data. -->
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)" />
<property name="openjpa.jdbc.DBDictionary" value="derby" />
<!-- EclipseLink specific properties to create the database. They are only used if using the jpa-2.1 feature. -->
<property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
<property name="eclipselink.ddl-generation.output-mode" value="both" />
</properties>
</persistence-unit>
</persistence>
I think your error is not caused by the OpenJPA jars not being available. It might be because your database is not configured correctly. Make sure your persistence.xml file refers to your datasources properly.

Referencing entities from other jars in EAR

I'm trying to create a layered web proyect with an EAR. I divided the Entities from the DataAccess in order to only allow DataAccess to be called by BusinessLogic.
I'm actually getting this exception:
Object: co.edu.icesi.i2trading.entities.Statetype#21397ba0 is not a known entity type.
And I found here that I need to create a persistence.xml in the EAR, but I can't really understand how.
Sharing a persistence unit across components in a .ear file
I tried placing the XML file in the Configuration Files:
And referencing the jar with <jar-files> in the persistence.xml;
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="I2TradingDataAccessPU" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>jdbc/I2DataSource</jta-data-source>
<jar-file>../I2TradingEntities.jar</jar-file>
<jar-file>../../I2TradingEntities.jar</jar-file>
<shared-cache-mode>NONE</shared-cache-mode>
<properties>
<property name="eclipselink.target-server" value="None"/>
<!-- <property name="eclipselink.logging.level" value="ALL"/> -->
<property name="eclipselink.logging.level" value="WARNING"/>
</properties>
</persistence-unit>
</persistence>
With no success. Any idea why? I'm very new to Web Developing and this is getting to my nerves.
I'm also getting this WARNING in the persistence.xml's DESIGN tab:

I believe that the instruction jar-file interprets any path from the file that holds the persistence.xml... So, your configuration specifies that the Entities JAR are siblings of your EAR file.
The best (and easy) solution for your problem is to put the given persistence.xmlat the META-INF folder of your I2TradingEntities.jar and remove the <jar-file> instructions from it ... This will instruct the Application Server to create a PersistenceContext called "I2TradingDataAccessPU" and to detect any #Entity Class contained in that JAR.

No Entity metadata found for the class

I'm back with the same problem ...
I'm trying to uses queries in my Cassandra DB with Kundera (Cassandra ORM), this queries work in an others project but when I try to do it in webapp (using tomcat 6.0), I got this error :
com.impetus.kundera.metadata.KunderaMetadataManager - No Entity metadata found for the class
=> JavaNullPointerException.
But when I leave the persistence.xml from my project I got an other error. (NoPersistence.xml found or something ... )
So, my project found Persistence.xml, but not my Entity class : fileCassandra.
You can see my persistence.xml :
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<!-- 192.168.3.107 -->
<persistence-unit name="cassandra_pu">
<provider>com.impetus.kundera.KunderaPersistence</provider>
<class>net.***.common.db.***.FileCassandra</class>
<properties>
<property name="kundera.nodes" value="localhost"/>
<property name="kundera.port" value="9160"/>
<property name="kundera.keyspace" value="KunderaExamples"/>
<property name="kundera.dialect" value="cassandra"/>
<property name="kundera.client.lookup.class" value="com.impetus.client.cassandra.pelops.PelopsClientFactory" />
<property name="kundera.cache.provider.class" value="com.impetus.kundera.cache.ehcache.EhCacheProvider"/>
<!-- <property name="kundera.cache.config.resource" value="/ehcache-test.xml"/> -->
</properties>
</persistence-unit>
</persistence>
net..common.db..FileCassandra I must replace by * because it's name from my companie ;)
The same methods (include EntityManager) works in junit on other project, when I build my project in Tomcat, this error appears ...

This happens when you have multiple entries of the same class in your classpath.
The ideal place to have your entities is closest to the same class loader which loads kundera core and client(HBase, Cassandra etc.).
For example, if these kundera files are under WEB-INF/lib, you'd rather have your entities under the application where as if kundera files are on the applications lib folder, better bundle your entities in a jar and put them there (and remove the entities in your app).

Only issue which i can see is classes and persistence.xml location.
try to place persistence.xml within /WEB-INF/classes/META-INF/, Provided that your entity definitions are within classes folder!
-Vivek

Unable to access datasource remotely through JBoss

Context
I have a JBoss where I have sucessfully deployed a datasource mydatasource-ds.xml.
It's JNDI name is java:mydatasourceDS. JBoss claims that the datasource is succesfully deployed. The JMX console agress too.
Problem
I want to use this datasource from a client java app launched on a separate JVM.
But I get an exception saying the java:mydatasourceDS cannot be found.
java.lang.ClassCastException: javax.naming.Reference cannot be cast to javax.sql.DataSource
Details
Here is the persistence.xml file :
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="mydatasource-db" transaction-type="JTA">
<jta-data-source>java:mydatasourceDS</jta-data-source>
<properties>
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.format_sql" value="true" />
<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.default_schema" value="rec" />
<property name="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.JBossTransactionManagerLookup"/>
</properties>
</persistence-unit>
Here is the jndi.properties file :
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.provider.url=jnp://localhost:1099
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
Here is the application classpath :
jndi.properties
log4j.properties
META-INF\persistence.xml
hibernate-jpa-2.0-api-1.0.0.Final.jar
jnp-client-5.0.3.GA.jar
jboss-common-core-2.2.14.GA.jar
jboss-logging-spi-2.1.0.GA.jar
hibernate-entitymanager-3.6.4.Final.jar
hibernate-core-3.6.4.Final.jar
antlr-2.7.6.jar
commons-collections-3.1.jar
dom4j-1.6.1.jar
hibernate-commons-annotations-3.2.0.Final.jar
jta-1.1.jar
javassist-3.12.0.GA.jar
slf4j-api-1.6.1.jar
slf4j-log4j12-1.6.1.jar
log4j-1.2.16.jar
xstream-1.4.1.jar
xmlpull-1.1.3.1.jar
xpp3_min-1.1.4c.jar
EDIT
I have found the source of the problem. The javax.sql.DataSource that was available to my client application was NOT the one received from JNDI. The one I receive from JNDI is the JBoss javax.sql.DataSource. Same name BUT slightly different classes hence the ClassCastException...
As of this writing, the JBoss javax.sql.DataSource can be found in this package : jboss-j2ee-4.2.3.GA.jar

If you get a
javax.naming.Reference
that means you are missing runtime dependencies that are required for it to resolve. You can inspect the classFactory member of the Reference object via
getFactoryClassName()
to figure out the first dependency you are missing.
In my case using JBoss6.1 it was:
org.jboss.resource.adapter.jdbc.remote.DataSourceFactory
Putting the jar this class is in on the classpath (common/lib/jbosscx-client.jar) got me past the first step and then it was a matter of tracking down all the ClassNotFoundException errors.
The full list for JBoss6.1 turned out to be:
- client/jnp-client.jar
- client/jboss-logging.jar
- common/lib/jbosscx-client.jar
- client/concurrent.jar
- client/jboss-client.jar
- client/jboss-common-core.jar
- client/jboss-integration.jar
- client/jboss-remoting.jar
- client/jboss-security-spi.jar
- client/jboss-serialization.jar
- client/jboss-transaction-api_1.1_spec.jar

This guide says that you have to set
<use-java-context>false</use-java-context>
in mydatasource-ds.xml. Not sure if you did.

Entities not mapped after moving them into external jar package

In my Java/Seam/JbossAS app, I decided to externalize my Model classes (hibernate entities) and moved them into another project. The project produces model.jar, which is then used by the main app. The model.jar dependency is resolved by Ivy.
Building the main app with Ant works without problems. Then I copy manually the model.jar into 'mainapp.ear/lib' directory. Afterwards I deploy the app and there are no problems (although I notice that there are is no log info about found mappings). But when I want to login, I get the exception:
javax.el.ELException: javax.ejb.EJBTransactionRolledbackException:
org.hibernate.hql.ast.QuerySyntaxException: AppUser is not
mapped [select u from AppUser u where u.userName = :usernamePar]
There were no code changes in the meantime, just externalizing some of the classes into a jar. Does this mean, that I need the source code of the Model classes when compiling the main app?

The EntityManagerFactory is built for scanning entities only from the jar that has a /META-INF/persistence.xml file into.
In order to scan other jars you have to use <jar-file>:
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="manager1" transaction-type="JTA">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>java:/DefaultDS</jta-data-source>
<mapping-file>ormap.xml</mapping-file>
<jar-file>MyApp.jar</jar-file>
<class>org.acme.Employee</class>
<class>org.acme.Person</class>
<class>org.acme.Address</class>
<shared-cache-mode>ENABLE_SELECTOVE</shared-cache-mode>
<validation-mode>CALLBACK</validation-mode>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
<property name="hibernate.hbm2ddl.auto" value="create-drop"/>
</properties>
</persistence-unit>
</persistence>
See 2.2.1 Packaging in Hibernate doc.

Also check if your hibernate mappings are correctly placed wrt hibernate config file. Note that hibernate mapping resources or classes are relative to the location of hibernate.cfg.xml file.