11:36:14,666DEBUG SecurityAssociation:143 - Using ThreadLocal: false
11:36:14,715DEBUG Client:514 - invoke called, but our invoker is disconnected, discarding and fetching another fresh invoker for: InvokerLocator [socket://127.0.0.2:3873/]
11:36:14,715DEBUG SocketClientInvoker:275 - connect called for: org.jboss.remoting.transport.socket.SocketClientInvoker@15d56d5
javax.ejb.EJBException: java.lang.IllegalArgumentException: org.hibernate.hql.ast.QuerySyntaxException: USR is not mapped [SELECT DISTINCT OBJECT(k) FROM USR k WHERE k.username = ?1]
...

Caused by: org.hibernate.hql.ast.QuerySyntaxException: USR is not mapped [SELECT DISTINCT OBJECT(k) FROM USR k WHERE k.username = ?1]
at org.hibernate.hql.ast.util.SessionFactoryHelper.requireClassPersister(SessionFactoryHelper.java:158)

    public Usr getUsrByUsername(String _username) throws UsernameException {
            if(_username==null) throw new UsernameException("The username value cannot be null.");
            Usr user = (Usr)em.createQuery("SELECT DISTINCT OBJECT(k) " +
                    "FROM USR k WHERE k.username = ?1").getSingleResult();
            return user;
        }

    <?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="Users-EJBModulePU" transaction-type="RESOURCE_LOCAL">
            <!-- Jboss uses hibernate as default persistence engine
            <provider>org.hibernate.ejb.HibernatePersistence</provider> -->
            <jta-data-source>java:/MySqlDS</jta-data-source>
            <exclude-unlisted-classes>false</exclude-unlisted-classes>
            <properties>
                <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
                <!-- Show and print nice SQL on stdout -->
                <property name="hibernate.show_sql" value="true"/>
                <property name="hibernate.format_sql" value="true"/>
                <!-- Drop and create a new DB each time - Use only on development-->
                <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
            </properties>
        </persistence-unit>
    </persistence>

    @Entity
    @Table(name="USR")
    public class Usr implements java.io.Serializable {

    <?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="Users-EJBModulePU" transaction-type="RESOURCE_LOCAL">
        <!-- Jboss uses hibernate as default persistence engine
            <provider>org.hibernate.ejb.HibernatePersistence</provider> -->
        <jta-data-source>java:/MySqlDS</jta-data-source>
        <class>eu.virtualLab.users.model.Usr</class>
        <exclude-unlisted-classes>true</exclude-unlisted-classes>
        <properties>
          <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
          <!-- Show and print nice SQL on stdout -->
          <property name="hibernate.show_sql" value="true"/>
          <property name="hibernate.format_sql" value="true"/>
          <!-- Use it just in development -->
          <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
        </properties>
      </persistence-unit>
    </persistence>