Erreur lors de linjection de ressources dans le bean géré

package business;
import entity.Utilisateur;
import java.util.List;
import javax.ejb.Stateless;
import javax.ejb.LocalBean;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
@Stateless
@LocalBean
public class UserBean {
    @PersistenceContext(unitName = "EnterpriseApplication4-ejbPU")
    private EntityManager em;
   public List<Utilisateur> getAllUsers(){
       Query query = em.createNamedQuery("select u from Utilisateur u");  
        return query.getResultList();  
   }
    public void persist(Utilisateur USer) {
        em.getTransaction().begin(); 
        em.persist(USer);
    }
}
persistance.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/persistence/index.html" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/persistence/index.html http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="EnterpriseApplication4-ejbPU" transaction-type="JTA">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <jta-data-source>User4</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlistansed-classes>
    <properties>
      <property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
    </properties>
  </persistence-unit>
</persistence>
managed bean
package manager;
import business.UserBean;
import entity.Utilisateur;
import java.io.Serializable;
import java.util.List;
import javax.ejb.EJB;
import javax.enterprise.context.SessionScoped;
import javax.faces.bean.ManagedBean;
import javax.inject.Named;
import model.UserModel;
/**
 *
 * @author axl
 */
@ManagedBean
@SessionScoped
@Named("UserBean")
public class UserManager implements Serializable {
    @EJB
    private UserBean userBean;
    @EJB
    Utilisateur u;
    UserModel user = new UserModel();
    public UserModel getUser() {
        return user;
    }
    public void setUser(UserModel user) {
        this.user = user;
    }
    /**
     * Creates a new instance of UserManager
     */
    public UserManager() {
    }
       public List<Utilisateur> getAllUser(){
        return userBean.getAllUsers();
    }
    public String ajouter(){
         u.setNom(user.getNom());
         u.setPrenom(user.getPrenom());
         u.setLogin(user.getLogin());
         u.setPassword(user.getPassword());
        userBean.persist(u);
        return "inscription";}
}