JPA JoinTable with additional columns - spring-boot

Question

Spring Boot
Spring Data
JPA Hibernate
Came across a requirement where JPA ManyToMany relationship table with an extra column. Have looked at StackOverflow and found several questions related to same requirement. Most of the answers on the forums ask for EmbeddedId field with a composite primary key with two columns. I tried the solutions from the forums, here is the code snippet.
#Data
#Entity
#Table (name = "TABLE_A")
public class TableA {
#Id
#Column (name = "table_a_id")
private Integer id;
...
#OneToMany (mappedBy = "pk.tableA")
private List<TableABMapping> mappingTable;
}
#Data
#Entity
#Table (name = "TABLE_B")
public class TableB {
#Id
#Column (name = "table_b_id")
private Integer id;
...
#OneToMany (mappedBy = "pk.tableB")
private List<TableABMapping> mappingTable;
}
#Data
#Entity
#Table (name = "TABLE_A_TABLE_B_MAPPING")
public class TableABMapping implements Serializable {
#EmbeddedId
private MappingKey pk = new MappingKey();
#Column(name = "addon_field")
private Double additionalField;
#Transient
public TableA getTableA() {
return getPk().getTableA();
}
public void setTableA(TableA tableA) {
getPk().setTableA(tableA);
}
#Transient
public TableB getTableB() {
return getPk().getTableB();
}
public void setTableB(TableB tableB) {
getPk().setTableB(tableB);
}
// equals() & hashCode() method override
}
#Data
#Embeddable
public class MappingKey implements Serializable {
#ManyToOne
#JoinColumn(name = "table_a_id", referencedColumnName = "table_a_id")
private TableA tableA;
#ManyToOne
#JoinColumn(name = "table_b_id", referencedColumnName = "table_b_id")
private TableB tableB;
// No argument constructor, two arguments constructor.
// equals() & hashCode() method override
}
Trying save operation from service class like this:
for (TableB tabB : tableA.getTableB()) {
TableABMapping abMapping = new TableABMapping();
abMapping.setTableA(tableA);
abMapping.setProduct(tabB);
abMapping.setAdditionalField(tabB.getAddonField());
if (tableA.getMappingTable() == null) {
tableA.setMappingTable(new ArrayList<TableABMapping>());
}
tableA.getMappingTable().add(abMapping);
}
TableA ta = tableARepository.save(tableA);
System.out.println("TableA.save(): " + ta);
Getting this error on save operation.
Unable to find TableABMapping with id MappingKey(tableA = TableA( ... ), tableB = TableB ( ... ))
Both the entities have proper ids at the time of saving the entity. But still it throws this error. Where I am making mistake?