聲明的元模型屬性工作正常BUT繼承元模型屬性爲NULL。爲什麼？

Question

我不能夠運行下面的測試： -

@Test 
public void test() { 
    EntityManager em = entityManagerFactory.createEntityManager(); 
    em.getTransaction().begin(); 

    CriteriaBuilder builder = em.getCriteriaBuilder(); 
    CriteriaQuery<Project> query = builder.createQuery(Project.class); 

    Root<Project> project = query.from(Project.class); 

    Path<String> name = project.get(Project_.name); 
    Assert.assertNotNull(name); 

    Path<EntityLifeCycleImpl> lifeCycle = project.get(Project_.lifeCycle); // problem is here, throws NullPointer 
    Assert.assertNotNull(lifeCycle); 
} 

它在project.get(Project_.lifeCycle)行拋出NullPointerException異常。爲什麼？

java.lang.NullPointerException 
    at org.hibernate.ejb.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:138) 

PersistenceEntityBase.java

import org.hibernate.annotations.GenericGenerator; 
     @MappedSuperclass 
@Access(AccessType.PROPERTY) 
public abstract class PersistentEntityBase { 

protected String identifier; 

protected EntityLifeCycleImpl lifeCycle = new EntityLifeCycleImpl(); 

protected PersistentEntityBase() { 
} 

@Id 
@GeneratedValue(generator="generator") 
@GenericGenerator(name="generator", strategy="guid", parameters = {}) 
@Column(name="identifier") 
public String getIdentifier() { 
    return identifier; 
} 

public void setIdentifier(String identifier) { 
    this.identifier = identifier; 
} 

@Embedded 
public EntityLifeCycleImpl getLifeCycle() { 
    return lifeCycle; 
} 
public void setLifeCycle(EntityLifeCycleImpl lifeCycle) { 
    this.lifeCycle = lifeCycle; 
} 

}

Project.java

@Entity 
@Table(name="project") 
@Access(AccessType.PROPERTY) 
public class Project extends PersistentEntityBase { 

    private String name; 

    protected Project() { 
    } 

    public Project(String name) { 
     this(); 
     this.name = name; 
    } 

    @Column(name="name", nullable=false, unique=true) 
    public String getName() { 
     return name; 
} 
public void setName(String name) { 
    this.name = name; 
} 

}

EntityLifeCycleImpl.java

@Embeddable 
public class EntityLifeCycleImpl implements EntityLifeCycle { 
    private String createdBy; 
    private Date createdDate; 
     @Column(name="created_by") 
public String getCreatedBy() { 
    return createdBy; 
} 
public void setCreatedBy(String createdBy) { 

    this.createdBy = createdBy; 
} 

@Column(name="created_date") 
public Date getCreatedDate() { 
    return createdDate; 
} 
public void setCreatedDate(Date createdDate) { 
    this.createdDate = createdDate; 
} 

}

PersistentEntityBase_.java（使用休眠元模型生成器生成的）

@StaticMetamodel(PersistentEntityBase.class) 
public abstract class PersistentEntityBase_ { 
    public static volatile SingularAttribute<PersistentEntityBase, EntityLifeCycleImpl> lifeCycle; 
     public static volatile SingularAttribute<PersistentEntityBase, String> identifier; 
    } 

Project_.java

@StaticMetamodel(Project.class) 
public abstract class Project_ extends PersistentEntityBase_ { 
    public static volatile SingularAttribute<Project, String> name; 
    } 

EntityLifeCycleImpl_.java

@StaticMetamodel(EntityLifeCycleImpl.class) 
public abstract class EntityLifeCycleImpl_ { 
    public static volatile SingularAttribute<EntityLifeCycleImpl, String> createdBy; 
    public static volatile SingularAttribute<EntityLifeCycleImpl, Date> createdDate; 
} 

的persistence.xml（僅relavent部分）

<class>com.comp.timetracking.entity.PersistentEntityBase</class> 
<class>com.comp.timetracking.entity.Project</class> 

編輯： 我使用hibernate-entitymanager.3.6.0.Final和hibernate-jpamodelgen.1.0.0.Final。

EDIT 2 @Pascal
我覺得休眠EM 3.6.0.Final使我們能夠在@Entity級別定義@Embedded註釋字段，但它在@MappedSuperclass水平否認這樣的領域。你說什麼？

因爲我在這裏看不到「文件上傳選項」，所以我在我的esnips帳戶中上傳了TestCase。 Download基於Maven的項目並運行SingularAttributeTest.java。和檢查用控制檯輸出

ERROR main metamodel.MetadataContext:413 - Unable to locate static metamodel field : timetracking.entity.Employee_#lifeCycle 

點擊「下載embedded-singular-attribute.zip」鏈接下載該文件，而無需安裝下載管理器。 （如果你點擊Download link with Green arrow，你將不得不安裝下載管理器!!）

Answer 1

我使用EclipseLink測試了你的類和測試用例（我刪除了Hibernate的特定部分）並通過了測試。但是，Hibernate 3.5.6確實失敗了。看起來像Hibernate中的一個bug。

順便說一句，你缺少一個Temporal註釋在Embeddable

@Column(name = "created_date") 
@Temporal(TemporalType.DATE) 
public Date getCreatedDate() { 
    return createdDate; 
} 

而且你不應該宣佈在persistence.xmlPersistentEntityBase（映射超類不是一個實體）。

Answer 2

我有同樣的問題：在部署了JBoss 7.0.2報告下列錯誤： 「無法找到靜態元模型場X」 其中X是從@MappedSuperclass繼承與@Embedded註解一個字段（ X的類型是用@Embeddable註解的類）。

我解決了它在由持久單元管理的類列表中添加用@Embeddable和@MappedSuperclass註解的類以及用@Entity註釋的類。這是在「persistence.xml」文件中配置的。

Answer 3

這不是問題。

Hibernate文檔：

If class X extends another class S, where S is the most derived managed class (i.e., entity or mapped superclass) extended by X, then class X_ must extend class S_, where S_ is the metamodel class created for S.

https://docs.jboss.org/hibernate/entitymanager/3.5/reference/en/html/metamodel.html