salut tous le monde quand je génère mon application j'ai l'erreur suivante Erreur lors de l?injection de ressources dans le bean géré «userManager»

voici mon ejb
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://java.sun.com/xml/ns/persistence" xmlnssi="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="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";}


}