DEBUG [org.jboss.as.jpa.messages] (MSC service thread 1-1) persistence unit search for unitName=null referenced from class=the.spring.Bean (annotation=@javax.persistence.PersistenceContext() on void the.spring.Bean.setEntityManager(javax.persistence.EntityManager))

<jboss-deployment-structure xmlns="urn:jboss:deployment-structure:1.2">
  <deployment>
    <exclusions>
      <module name="deployment.jee-app.war.spring-app.jar" />
      <!-- I have also tried the following -->
      <!-- <module name="jee-app.war.spring-app.jar" /> -->
      <!-- <module name="spring-app.jar" /> -->
    </exclusions>
  </deployment>
</jboss-deployment-structure>

<scanning xmlns="urn:jboss:scanning:1.0">
  <path name="jee-app.war/WEB-INF/lib">
    <exclude name="spring-app.jar" />
  </path>
</scanning>

jee-app.war
  ├── WEB-INF
  │   ├── classes
  |   │   ├── META-INF
  |   │   |    └── persistence.xml _____________ # 2 PUs here
  |   |   └── < lots of packages >
  |   ├── lib
  |   |   ├── spring-app.jar ___________________ # to EXCLUDE from scanning !!!
  |   |   |   ├── META-INF
  |   |   |   |   └── persistence
  |   |   |   |       └── persistence.xml ______ # 1 PU here, loaded by Spring
  |   |   |   ├── application.xml ______________ # Spring definition
  |   |   |   └── the
  |   |   |       └── spring
  |   |   |           └── Bean.class
  |   |   └── < lots of other jars >
  |   ├── jboss-deployment-structure.xml
  |   ├── jboss-scanning.xml
  |   └── web.xml
  └── < some JSPs >

<?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="PU1" transaction-type="JTA">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
    <jta-data-source>java:jboss/datasources/DS1</jta-data-source>
    <class>...</class> <!-- a lot of classes included by name !-->
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
      <property name="hibernate.hbm2ddl.auto" value="update" />
      <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.EhCacheProvider" />
      <property name="hibernate.show_sql" value="true" />
      <property name="hibernate.format_sql" value="false" />
    </properties>
  </persistence-unit>

  <persistence-unit name="PU2" transaction-type="JTA">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
    <jta-data-source>java:jboss/datasources/DS2</jta-data-source>
    <class>...</class> <!-- a lot of classes included by name !-->
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
      <property name="hibernate.hbm2ddl.auto" value="update" />
      <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.EhCacheProvider" />
      <property name="hibernate.show_sql" value="true" />
      <property name="hibernate.format_sql" value="false" />
    </properties>
  </persistence-unit>
</persistence>

<?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" version="1.0" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="xa-rm">

    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <mapping-file>META-INF/persistence/orm.xml</mapping-file>

    <exclude-unlisted-classes>false</exclude-unlisted-classes>

  </persistence-unit>