How can I pessimistically lock an Entity in JBoss and Hibernate?

Issue

• I am trying to find a way to synchronize access to some POJO entities in a EAP 5.1 environment.
• I need is to have a transaction hold a lock on and entity and release the lock at the end while other transactions "wait" for the lock to become available.

• When using em.lock(Object, LockModeType.WRITE) and another transaction is trying to put a lock on an already locked object, I'm receiving the following error:

  Caused by: org.hibernate.exception.LockAcquisitionException: could not lock: [com.company.entity.Order#39578404]
  at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:110)
  at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
  at org.hibernate.dialect.lock.SelectLockingStrategy.lock(SelectLockingStrategy.java:115)
  at org.hibernate.persister.entity.AbstractEntityPersister.lock(AbstractEntityPersister.java:1352)
  at org.hibernate.event.def.AbstractLockUpgradeEventListener.upgradeLock(AbstractLockUpgradeEventListener.java:108)
  at org.hibernate.event.def.DefaultLockEventListener.onLock(DefaultLockEventListener.java:87)
  at org.hibernate.impl.SessionImpl.fireLock(SessionImpl.java:613)
  at org.hibernate.impl.SessionImpl.lock(SessionImpl.java:605)
        at org.hibernate.ejb.AbstractEntityManagerImpl.lock(AbstractEntityManagerImpl.java:383)
        ... 135 more
   Caused by: java.sql.SQLException: ORA-00054: resource busy and acquire with NOWAIT specified
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
        at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:331)
        at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:288)
        at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:745)
        at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:219)
        at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:813)
        at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1049)
        at oracle.jdbc.driver.T4CPreparedStatement.executeMaybeDescribe(T4CPreparedStatement.java:854)
        at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1154)
        at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3370)
        at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3415)
        at org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.executeQuery(WrappedPreparedStatement.java:342)
        at org.hibernate.dialect.lock.SelectLockingStrategy.lock(SelectLockingStrategy.java:95)