java - 应用泛型类@MappedSuperclass作为targetEntity.Error : @ManyToOne on models. Unit.parent引用未知实体: models. GenericHierarchic

Question

我有扩展其他泛型类的泛型类。它们都是@MappedSuperclass。所以他们在数据库中没有自己的表。它们也是抽象的，因此它们没有任何对象。它们只是我的实体 @Entity

的骨架

我的继承结构:

通用 -> GenericDictionary -> GenericHierarchicalDictionary -> 单位

其中 Unit 是 @Entity 类并具有对象。

@Entity
public class Unit extends GenericHierarchicalDictionary<Unit> {}

单元实体具有层次结构，这意味着实体与其自身有关系，但我为此使用抽象类(@MappedSuperclass)，所以我想定义它动态地在该抽象类中:

我的 GenericHierarchicalDictionary:

@MappedSuperclass
public abstract class GenericHierarchicalDictionary<T extends Generic<T>> extends GenericDictionary<T> {
    @Required
    @ManyToOne(targetEntity = GenericHierarchicalDictionary.class, fetch=FetchType.LAZY, cascade = {CascadeType.ALL})
    @JoinColumn(name="parent_id")
    public GenericHierarchicalDictionary<T> parent;

但是 id 不起作用。我收到错误:

play.api.UnexpectedException: Unexpected exception[PersistenceException: [PersistenceUnit: defaultPersistenceUnit] Unable to configure EntityManagerFactory]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:148) ~[play_2.10.jar:2.2.4]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:112) ~[play_2.10.jar:2.2.4]
        at scala.Option.map(Option.scala:145) ~[scala-library.jar:na]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1.apply(ApplicationProvider.scala:112) ~[play_2.10.jar:2.2.4]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1.apply(ApplicationProvider.scala:110) ~[play_2.10.jar:2.2.4]
        at scala.util.Success.flatMap(Try.scala:200) ~[scala-library.jar:na]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: defaultPersistenceUnit] Unable to configure EntityManagerFactory
        at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:378) ~[hibernate-entitymanager-3.6.9.Final.jar:3.6.9.Final]
        at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:56) ~[hibernate-entitymanager-3.6.9.Final.jar:3.6.9.Final]
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63) ~[hibernate-jpa-2.0-api.jar:1.0.1.Final]
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47) ~[hibernate-jpa-2.0-api.jar:1.0.1.Final]
        at play.db.jpa.JPAPlugin.onStart(JPAPlugin.java:35) ~[play-java-jpa_2.10.jar:2.2.4]
        at play.api.Play$$anonfun$start$1$$anonfun$apply$mcV$sp$1.apply(Play.scala:88) ~[play_2.10.jar:2.2.4]
Caused by: org.hibernate.AnnotationException: @OneToOne or @ManyToOne on models.Unit.parent references an unknown entity: models.GenericHierarchicalDictionary
        at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:107) ~[hibernate-core-3.6.9.Final.jar:3.6.9.Final]
        at org.hibernate.cfg.Configuration.processEndOfQueue(Configuration.java:1580) ~[hibernate-core-3.6.9.Final.jar:3.6.9.Final]
        at org.hibernate.cfg.Configuration.processFkSecondPassInOrder(Configuration.java:1503) ~[hibernate-core-3.6.9.Final.jar:3.6.9.Final]
        at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1419) ~[hibernate-core-3.6.9.Final.jar:3.6.9.Final]
        at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1375) ~[hibernate-core-3.6.9.Final.jar:3.6.9.Final]
        at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1519) ~[hibernate-entitymanager-3.6.9.Final.jar:3.6.9.Final]

如果我纠正了这个错误，我应该为 targetEntity 分配一个带有 @Entity 注释的 java 类，但这不是我想要的。

我希望从实体的上下文中动态声明 @ManyToOne targetEntity。

我怎样才能实现这个目标？请给我一些帮助。

Answer 1

这是我在 spring 中实现的分层泛型类(抽象、映射父类(super class)):

import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.FetchType;
import javax.persistence.ManyToOne;
import javax.persistence.MappedSuperclass;
import javax.persistence.OneToMany;



@MappedSuperclass
public abstract class GenericHierarchicalModel<T extends GenericHierarchicalModel<T>> extends GenericModel<T> {
    private String name;
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private T parent;
    @OneToMany(mappedBy = "parent")
    private List<T> children;

    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
    public T getParent() {return parent;}
    public void setParent(T parent) {this.parent = parent;}
    public List<T> getChildren() {return children;}
    public void setChildren(List<T> children) {this.children = children;}


    public GenericHierarchicalModel() {
        super();
    }
    public GenericHierarchicalModel(Long id) {
        super(id);
    }
    public GenericHierarchicalModel(Long id, String name) {
        super(id);
        this.name = name;
    }
    public GenericHierarchicalModel(Long id, String name, List<T> children) {
        super(id);
        this.name = name;
        this.children = children;
    }

完成所有工作。我有基于它的工作实现类。希望我能帮忙。

查看此帖子: Java hibernate/jpa how to create dynamic generic entity that is self related