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

I have the following relational entities in database:

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 contains foreign keys to Table A and J. Table C contains foreign keys to Table B and J.

Note: Both Table B and C contain a foreign key reference (TABLE_J_ID), referencing Table J.

As you can see, both Table B and C have Many-to-One relation with Table J. As such, I have created the following bidirectional entities:

@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;

}    

The way the object graph/tree is built:

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);
    }

  }
}

When I execute the code, I get the following error:

**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**

Can someone tell me what the issue is?

Answer 1

The issue is:

First A is inserted. Then A_ID is used as FK in B. B is inserted. B also needs J_ID FK, but J was not stored yet = transient.

The order how JPA is creating inserts should be changed. J_ID is needed to create B,C. Persist J before adding it to B,C.

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

also the other loop