java - Embeddable、Hibernate 中的多对一关系

Question

我有一个场景，hibernate 中的 Embeddable 类使用Entity。根据我在SO和其他链接上找到的各种答案，我们可以在Embeddable类中编写@ManyToOne，@OneToMany。

但是这样做会给我 HibernateMappingExeption

考虑以下示例:我有两个实体和一个可嵌入类，如下所示:

实体A

@Entity
@Table(name = "A")
public class A {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int a_id;

    @ElementCollection
    @JoinTable(name = "embeded_class_table", joinColumns = @JoinColumn(name = "a_id"))
    private List<EmbeddedClass> embeddedClass;

实体B

@Entity
@Table(name = "B")
public class B {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int b_id;

使用实体 B 的嵌入式类

@Embeddable
public class EmbeddableClass {

    @ManyToOne
    @JoinColumn(name = "b_id")
    private B b;

我收到的错误如下:

org.hibernate.MappingException: Could not determine type for: app.model.B, at table: embeded_class_table, for columns: [org.hibernate.mapping.Column(b)]

有人可以建议我是否正确使用这些东西，如果是的话，我错过了什么？

Answer 1

假设您的情况我尝试了以下操作，但没有遇到任何问题:

@Entity
@Table(name = "A")
public class A {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int a_id;

    @ElementCollection
    @JoinTable(name = "embeded_class_table", joinColumns = @JoinColumn(name = "a_id"))
    private List<EmbeddableClass> embeddedClass;

    public int getA_id() {
        return a_id;
    }

    public void setA_id(int a_id) {
        this.a_id = a_id;
    }

    public List<EmbeddableClass> getEmbeddedClass() {
        return embeddedClass;
    }

    public void setEmbeddedClass(List<EmbeddableClass> embeddedClass) {
        this.embeddedClass = embeddedClass;
    }

}

@Entity
@Table(name = "B")
public class B {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int b_id;
}

@Embeddable
public class EmbeddableClass {

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "b_id")
    private B b;

    public B getB() {
        return b;
    }

    public void setB(B b) {
        this.b = b;
    }


}

hibernate.cfg.xml

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.bytecode.use_reflection_optimizer">false</property>
        <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
        <property name="hibernate.connection.password">xxxx</property>
        <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:xe</property>
        <property name="hibernate.connection.username">elias</property>
        <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>
        <property name="hibernate.hbm2ddl.auto">create-drop</property>
        <property name="show_sql">true</property>
        <mapping class="com.springex.dto.A"></mapping>
        <mapping class="com.springex.dto.B"></mapping>
        <mapping class="com.springex.dto.EmbeddableClass"></mapping>
    </session-factory>
</hibernate-configuration>