java - 未找到命名查询

Question

我使用 EJB 3，我试图从数据库获取一个简单的字符串，但我收到此消息

Named query not found: SELECT tr FROM Travauxdereseauurbain tr

我不太明白这意味着什么。

这是实体

@Entity
@Table(name="Travauxdereseauurbain")
public class Traveauxdereseauurbain implements Serializable {
    private static final long serialVersionUID = 1L;

@Id
@Column(name="idtru")
private int idtru;
@Column(name ="article")
private String article;
@Column (name="designationtraveau")
private String designationtraveau;
@Column(name="unite")
private String unite;
@Column(name="prixHTVA")
private float prixHTVA;
@Column(name="prixTTC")
private float prixTTC;
@Column (name="qtt")
private float qtt;
@Column(name="montantHTVA")
private float montantHTVA;
@Column(name="montantTTC")
private float montantTTC;


///GETTERS, SETTERS AND CONSTRUCTOR   
}

和 DAO 类

@Stateless
public class TravauxdereseauurbainDAO {     

    @PersistenceContext
    private EntityManager em;       

    public Traveauxdereseauurbain affichernimpr()
    {


      Query q =em.createNamedQuery("SELECT tr FROM Travauxdereseauurbain tr");

      return  (Traveauxdereseauurbain) q.getResultList().get(0);
    }
}

最后的错误消息是:

Servlet.service()" pour la servlet Faces Servlet a généré une exception: java.lang.IllegalArgumentException: Named query not found: SELECT tr FROM Travauxdereseauurbain tr

提前谢谢你

Answer 1

您没有调用正确的方法。您需要调用em.createQuery .