An UnsupportedOperationException is thrown on WebSphere Liberty, if an entity is persisted with a value, that causes a constaint violation in database (for example, if a column cannot hold a too long value).

Pseudo example:

/*
* create table APP_JOBS {
*    ID NUMBER(*,0) NOT NULL PRIMARY KEY,
*    JOB VARCHAR2(10 CHAR)
* }
* /

appJobsEntity.setJob("IAmTooLongForColumn");

@TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
saveMethod(appJobsEntity) {
   em.save(appJobsEntity);
}

//On save a exception is thrown:
javax.ejb.EJBTransactionRolledbackException: nested exception is: javax.transaction.RollbackException
at com.ibm.ejs.container.BusinessExceptionMappingStrategy.mapCSIException(BusinessExceptionMappingStrategy.java:124)
at com.ibm.ejs.container.BusinessExceptionMappingStrategy.mapCSITransactionRolledBackException(BusinessExceptionMappingStrategy.java:584)
at com.ibm.ejs.container.EJSDeployedSupport.mapCSITransactionRolledBackException(EJSDeployedSupport.java:600)
at com.ibm.ejs.container.EJSContainer.postInvokeRolledbackException(EJSContainer.java:4382)
at com.ibm.ejs.container.EJSContainer.postInvoke(EJSContainer.java:4073)
....
Caused by: java.lang.UnsupportedOperationException
at org.hibernate.engine.transaction.jta.platform.internal.WebSphereExtendedJtaPlatform$TransactionManagerAdapter.setRollbackOnly(WebSphereExtendedJtaPlatform.java:121)
at org.hibernate.resource.transaction.backend.jta.internal.JtaTransactionAdapterTransactionManagerImpl.markRollbackOnly(JtaTransactionAdapterTransactionManagerImpl.java:100)

Unlike the prior versions WebSphere Liberty 8.5.5.7 seems to provide access to the TransactionManager to support the rollback operation.
Suggested improvement of Hibernate: Add a WebSphereLibertyJtaPlatform like the one below (working example; jndi lookup didnt worked in my environment):

import javax.transaction.TransactionManager;
import javax.transaction.UserTransaction;
import org.hibernate.engine.transaction.jta.platform.internal.AbstractJtaPlatform;
//Get rid of this dependencies with reflection
import com.ibm.tx.jta.TransactionManagerFactory;
import com.ibm.tx.jta.UserTransactionFactory;

public class WebSphereLibertyJtaPlatform extends AbstractJtaPlatform {
	@Override
	protected TransactionManager locateTransactionManager() {
		return TransactionManagerFactory.getTransactionManager();
	}
	@Override
	protected UserTransaction locateUserTransaction() {
		return UserTransactionFactory.getUserTransaction();
	}
}