hibernate - 声明的元模型属性工作正常，但继承的元模型属性为 NULL。为什么？

Question

我无法运行以下测试:-

@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) 处抛出 NullPointerException线。为什么？

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;
}

}

项目.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 Hibernate Metamodel Generator 生成)

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

项目_.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;
}

持久性.xml (仅相关部分)

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

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

编辑 2
@帕斯卡
我认为 Hibernate EM 3.6.0.Final 允许我们定义 @Embedded注释字段位于 @Entity级别，但它在 @MappedSuperclass 拒绝此类字段等级。你怎么说？

由于我在这里看不到“文件上传选项”，我已经在我的 esnips 帐户中上传了 TestCase。 Download基于 maven 的项目并运行 SingularAttributeTest.java .并检查控制台输出

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

点击“ 下载内嵌奇异属性.zip ”链接下载文件，无需安装下载管理器。 (如果你点击 Download link with Green arrow ，你必须安装下载管理器!!)

Answer 1

我使用 EclipseLink 测试了您的类和测试用例(我删除了 Hibernate 特定部分)并且测试通过了。但它确实在 Hibernate 3.5.6 上失败了。看起来像 Hibernate 中的一个错误。

顺便说一下，您缺少一个 Temporal您的 Embeddable 中的注释

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

而且你不应该声明 PersistentEntityBase在 persistence.xml (映射的父类(super class)不是实体)。