java - 使用 hibernate 注解在 Java 中映射子类列表

Question

我在映射子类列表时遇到问题:
模型情况 - 我有一个抽象类:

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(
        name="shapeType",
        discriminatorType=DiscriminatorType.STRING
    )
public abstract class Shape{
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    protected Long id;

    @Column(name="owner_id")
    private Long ownerId;

    @ManyToOne
    @JoinColumn(updatable=false, insertable=false, name="owner_id")
    private Owner owner;
}

及其子类:

@Entity
@DiscriminatorValue(value="triangel")
public class Triangel extends Shape {
}

和:

@Entity
@DiscriminatorValue(value="circle")
public class Circle extends Shape {
}

然后，我有一个类Owner，它有一个子类列表:

@Entity
public class Owner {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "owner", targetEntity=Shape.class)
    private List<Triangel> triangels;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "owner", targetEntity=Shape.class)
    private List<Circle> circles;
}

当我循环遍历triangel列表时:

for(Object triangel: owner.getTriangels()){ //Using Triangel as a type throws ClassCastException
    logger.info(triangel.toString());
}

它迭代所有形状对象，而不仅仅是triangel对象。在我看来，在这种情况下，hibernate 在选择子类期间会忽略 DiscriminatorColumn 。

请注意，如果没有将 targetEntity 指定为 @OneToMany 中的 Shape.class，我的应用程序甚至无法启动，并且在映射方面存在一些问题初始化。

来自pom.xml的配置:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.34</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>4.3.7.Final</version>
</dependency>
<dependency>
    <groupId>org.hibernate.javax.persistence</groupId>
    <artifactId>hibernate-jpa-2.1-api</artifactId>
    <version>1.0.0.Final</version>
</dependency>
 <dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>javax.persistence</artifactId>
    <version>2.1.0</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>commons-dbcp</groupId>
    <artifactId>commons-dbcp</artifactId>
    <version>1.2.2</version>
    <scope>provided</scope>
</dependency>

我应该如何对该设计进行正确的映射配置？

Answer 1

这是最近在 Hibernate 5.2.7 中修复的问题:https://hibernate.atlassian.net/browse/HHH-11375