java - 如何在JPA/Hibernate的 child 的ID中引用 parent 的ID？

给定一个表（MY_TABLE_A），该表在每次新插入时自动增加其ID（即数据库中的第一条记录的ID属性设置为1，第二条记录的ID属性设置为2，第三条记录的ID属性设置为至3）。我在说的ID是表的主键。

我还有另一个表（MY_TABLE_B），该表引用原始表的主键。当我尝试将两者都持久保存到Oracle数据库时，我得到一个org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save()

我要完成的工作：每当我将对象持久保存到MY_TABLE_A时，我都希望MY_TABLE_B插入一个具有与MY_TABLE_A相同的ID的对象，因为它会自动递增（直到知道它的下一个值是多少）插入）。为了明确起见，表A中的一个ID在表B中应该只有一个匹配的ID

以下是我的代码的一些摘要：

头等舱：

@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_A")
@Component
public class FirstClass implements Serializable {

    @Id
    @SequenceGenerator(name = "MY_SEQ", sequenceName = "MY_SCHEMA.MY_SEQ", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MY_SEQ")
    @Column(name = "MY_ID")
    private Integer myId;
    // more variables, getters/setters
}

二等舱：

@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_B")
@SecondaryTable(name = "MY_SCHEMA.MY_TABLE_A", pkJoinColumns = @PrimaryKeyJoinColumn(name = "MY_ID", referencedColumnName = "MY_ID"))
@Component
public class SecondClass {

    @Id
    @Column(name = "MY_ID")
    private Integer myId;
    // more variables, getters/setters
}

我在其中为Oracle中的每个服务项插入新条目的服务层代码段：

firstClassService.insert();
secondClassService.insert();

firstClassService的insert()上的详细信息：

public void insert() {
        FirstClass obj = new FirstClass();
        getCurrentSession().persist(obj);
}

insert()用于secondClassService：

public void insert() {
        SecondClass obj = new SecondClass();
        getCurrentSession().persist(obj);
}

更新

FirstClass现在的样子：

@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_A")
@Component
public class FirstClass implements Serializable {

    @Id
    @SequenceGenerator(name = "MY_SEQ", sequenceName = "MY_SCHEMA.MY_SEQ", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MY_SEQ")
    @Column(name = "MY_ID")
    @OneToOne(mappedBy = "myId")
    private Integer myId;
}

二等舱：

@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_B")
@SecondaryTable(name = "MY_SCHEMA.MY_TABLE_B", pkJoinColumns = @PrimaryKeyJoinColumn(name = "MY_ID", referencedColumnName = "MY_ID"))
@Component
public class SecondClass implements Serializable {

    @Id
    @JoinColumn(name = "MY_ID", referencedColumnName = "MY_ID")
    @OneToOne
    private Integer restRequestId;
}

最佳答案

映射应如下所示：

@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_A")
@Component
public class FirstClass implements Serializable {

    @Id
    @SequenceGenerator(name = "MY_SEQ", sequenceName = "MY_SCHEMA.MY_SEQ", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MY_SEQ")
    @Column(name = "MY_ID")
    private Long myId;

    @OneToOne(mappedBy = "firstClass", cascade = CascadeType.ALL)
    private SecondClass secondClass;
}

@Entity
@Table(name = "MY_SCHEMA.MY_TABLE_B")
@Component
public class SecondClass implements Serializable {

    @Id
    @JoinColumn(name = "MY_ID", referencedColumnName = "MY_ID")
    @OneToOne
    private FirstClass firstClass;
}

设置Cascade选项后，您只需要调用保存firstClass的方法：关联的secondClass将自动持久化-假设您在内存模型中设置了关联关系的两侧，即

firstClass.setSecondClass(secondClass);
secondClass.setFirstClass(firstClass);