jpa/subsystem/src/main/java/org/jboss/as/jpa/container/PersistenceUnitSearch.java
private static PersistenceUnitMetadata findWithinDeployment(DeploymentUnit unit, String persistenceUnitName) {
        if (traceEnabled) {
            ROOT_LOGGER.tracef("pu findWithinDeployment searching for %s", persistenceUnitName);
        }

        for (ResourceRoot root : DeploymentUtils.allResourceRoots(unit)) {
            PersistenceUnitMetadataHolder holder = root.getAttachment(PersistenceUnitMetadataHolder.PERSISTENCE_UNITS);
            if (holder == null || holder.getPersistenceUnits() == null) {
                if (traceEnabled) {
                    ROOT_LOGGER.tracef("pu findWithinDeployment skipping empty pu holder for %s", persistenceUnitName);
                }
                continue;
            }

            ambiguousPUError(unit, persistenceUnitName, holder);
            persistenceUnitName = defaultPersistenceUnitName(persistenceUnitName, holder);

            for (PersistenceUnitMetadata persistenceUnit : holder.getPersistenceUnits()) {
                if (traceEnabled) {
                    ROOT_LOGGER.tracef("findWithinDeployment check '%s' against pu '%s'", persistenceUnitName, persistenceUnit.getPersistenceUnitName());
                }
                if (persistenceUnitName == null || persistenceUnitName.length() == 0 || persistenceUnit.getPersistenceUnitName().equals(persistenceUnitName)) {
                    if (traceEnabled) {
                        ROOT_LOGGER.tracef("findWithinDeployment matched '%s' against pu '%s'", persistenceUnitName, persistenceUnit.getPersistenceUnitName());
                    }
                    return persistenceUnit;
                }
            }
        }
        return null;
    }
private static PersistenceUnitMetadata findWithinDeployment(DeploymentUnit unit, String persistenceUnitName) {
        if (traceEnabled) {
            ROOT_LOGGER.tracef("pu findWithinDeployment searching for %s", persistenceUnitName);
        }

        for (ResourceRoot root : DeploymentUtils.allResourceRoots(unit)) {
            PersistenceUnitMetadataHolder holder = root.getAttachment(PersistenceUnitMetadataHolder.PERSISTENCE_UNITS);
            if (holder == null || holder.getPersistenceUnits() == null) {
                if (traceEnabled) {
                    ROOT_LOGGER.tracef("pu findWithinDeployment skipping empty pu holder for %s", persistenceUnitName);
                }
                continue;
            }

            ambiguousPUError(unit, persistenceUnitName, holder);
            persistenceUnitName = defaultPersistenceUnitName(persistenceUnitName, holder);

            for (PersistenceUnitMetadata persistenceUnit : holder.getPersistenceUnits()) {
                if (traceEnabled) {
                    ROOT_LOGGER.tracef("findWithinDeployment check '%s' against pu '%s'", persistenceUnitName, persistenceUnit.getPersistenceUnitName());
                }
                if (persistenceUnitName == null || persistenceUnitName.length() == 0 || persistenceUnit.getPersistenceUnitName().equals(persistenceUnitName)) {
                    if (traceEnabled) {
                        ROOT_LOGGER.tracef("findWithinDeployment matched '%s' against pu '%s'", persistenceUnitName, persistenceUnit.getPersistenceUnitName());
                    }
                    return persistenceUnit;
                }
            }
        }
        return null;
    }
/*
When finding the default persistence unit, the first persistence unit encountered is returned.