如何在 Hibernate 中持久化具有两个多对一双向依赖关系的实体？

Question

我在数据库中有以下关系实体：

Table A <-- (One-to-Many) --> Table B
Table B <-- (One-to-Many) --> Table C
Table B <-- (Many-to-One) --> Table J
Table C <-- (Many-to-One) --> Table J

Table B 包含 Table A 和 J 的外键。 Table C 包含 Table B 和 J 的外键。

注意：Table B 和 C 都包含外键引用 (TABLE_J_ID)，引用 Table J.

如您所见，Table B 和 C 都与 Table J 存在多对一关系。因此，我创建了以下双向实体：

@Entity
@Table(name="TableA")
public class TableA {
  @Id
  // Generates via a sequence object
  private Integer id;

  @OneToMany(mapped="tableATableB", cascade=CascadeType.All, orphanRemoval=true)
  private Set<TableB> tableBs = new LinkedHashSet<TableB>();

  public void addTableB(TableB b) {
    this.tableBs.add(b);
    b.setTableATableB(this);
  }
}

@Entity
@Table(name="TableB")
public class TableB {
  @Id
  // Generates via a sequence object
  private Integer id;

  @ManyToOne
  @JoinColumn(name="TABLE_J_ID")
  private TableJ tableJTableB;

  @ManyToOne
  @JoinColumn(name="TABLE_A_ID")
  private TableA tableATableB;

  @OneToMany(mapped="tableBTableC", cascade=CascadeType.All, orphanRemoval=true)
  private Set<TableC> tableCs = new LinkedHashSet<TableC>();

  public void addTableC(TableC c) {
    this.tableCs.add(c);
    b.setTableBTableC(this);
  }
}

@Entity
@Table(name="TableJ")
public class TableJ {
  @Id
  // Generates via a sequence object
  private Integer id;

  @OneToMany(mapped="tableJTableB", cascade=CascadeType.All)
  private Set<TableB> tableBs = new LinkedHashSet<TableB>();

  @OneToMany(mapped="tableJTableC", cascade=CascadeType.All)
  private Set<TableC> tableCs = new LinkedHashSet<TableC>();

  public void addTableB(TableB b) {
    this.tableBs.add(b);
    b.setTableJTableB(this);
  }

  public void addTableC(TableC c) {
    this.tableCs.add(c);
    b.setTableJTableC(this);
  }

}

@Entity
@Table(name="TableC")
public class TableC {
  @Id
  // Generates via a sequence object
  private Integer id;

  @ManyToOne
  @JoinColumn(name="TABLE_J_ID")
  private TableJ tableJTableC;

  @ManyToOne
  @JoinColumn(name="TABLE_B_ID")
  private TableB tableBTableC;

}

构建对象graph/tree的方式：

TableA tableA = new TableA();

// Get a list of TableB's (bList) from an external call
// THIS BASICALLY ADDS TABLE B's to TABLE A and TABLE J
for (TableB b : bList) {
  TableJ j = new TableJ();
  j.addTableB(b);

  tableA.addTableB(b);

}

// Get a list of TableC's (cList) from an external call
// THIS BASICALLY ADDS TABLE C's to TABLE B and TABLE J
for (TableC c : cList) {

  for (TableB b : tableA.getTableBs()) {
    // Iterate through bList and find a match per some logic
    if (/* some logic to find a corresponding TableB */) {
      TableJ j = new TableJ();
      j.addTableC(c);

      b.addTableC(c);
    }

  }
}

当我执行代码时，出现以下错误：

**Unexpected error occurred in scheduled task.: org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientPropertyValueException: object TableB.tableJTableB -> class TableJ; nested exception in java.lang.IllegalStateException: org.hibernate.TransientPropertyValueException: object references an unsaved transient instance - save the transient instance before flushing: TableB.tableJTableB -> class TableJ

Caused by: java.lang.IllegalStateException: org.hibernate.TransientPropertyValueException: object references an unsaved transient instance - save the transient instance before flushing: TableB.tableJTableB -> class TableJ**

谁能告诉我问题出在哪里？

Answer 1

问题是：

先插入A。然后在B中用A_ID作为FK，插入B。 B 还需要 J_ID FK，但 J 尚未存储 = 瞬态。

应更改 JPA 创建插入的顺序。 J_ID 需要创建 B,C。在将 J 添加到 B、C 之前保留 J。

for (TableB b : bList) {
  TableJ j = new TableJ();
  em.persist(j)
  j.addTableB(b);
  tableA.addTableB(b);
}

还有另一个循环

如何在 Hibernate 中持久化具有两个多对一双向依赖关系的实体？

How to Persist an Entity with Two Many-to-One Bidirectional Dependencies in Hibernate?

java

hibernate

jpa

many-to-one