休眠一对一映射不更新子表

Question

I have following Associated classes with one to one mapping.

@Entity
    public class EmployeeEntity
    {
      @Id
      private String id;

      private String name;


      @OneToOne(mappedBy = "employeeEntity", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
      @Fetch(FetchMode.SELECT)
      @JoinColumn(name = "empid")
      private AddressEntity addressEntity;
        ...
        ...
        getters & setters
    }


@Entity
public class AddressEntity
{
    @Id
    @Column(unique=true, nullable=false)
    @GeneratedValue(generator="gen")
    @GenericGenerator(name="gen", strategy="foreign", parameters=@Parameter(name="property", value="employeeEntity"))
    private String empId;

    @OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @PrimaryKeyJoinColumn
    private EmployeeEntity employeeEntity;
    ...
    getters & setters
}

I am using postgres and having tables (employeeentity, addressentity) with following foriegn key constraint on addressentity table: Foreign-key constraints: "fkakhilesh" FOREIGN KEY (empid) REFERENCES employeeentity(id) ON DELETE CASCADE

I have following requirements with different REST calls:

1. POST Rest call - should create an employee with address.
2. POST Rest call - should create an employee without address.
3. GET Rest call - should retrieve an employeee. Address should also come if it exist.
4. PUT Rest call - should update an employee and address (if address exists).
5. PUT Rest call - should update an employee and address (when address is passed and it already exists in addressentity table for empid)
6. PUT Rest call - should update an employee and create the address (when address is passed and it does not exists in addressentity table for empid)

I am able to perform operations 1 to 5 without any issues.

The main problem is in 6 and following questions come to my mind: 1. when i do "getSession().update(object)" , I get hibernate's StaleStateException: Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1. is this not possible with "update" if address does not exists? can't I create a new address during update?

1. do i need to change my ServiceImpl call to "getSession().merge(object) ? is this case can only be handled by calling "merge" ? how it impacts performance?

2. If i do merge, i get hibernate's IdentifierGenerationException: attempted to assign id from null one-to-one property. Am i missing something here?

3. this can be solved by changing hibernate mapping? or somethin related to cascade.

4. what is the importance of @GeneratedValue(generator="gen") here? why is @parameter used in @GenericGenerator

I am new to hibernate and trying to get into the depth of hibernate mapping. Also, I would be delighted if you could suggest me on the design as what should be the best way to handle this.

Answer 1

I got the fix for this. This one-one mapping is somewhat tricky and not simple as i thought initially. I have used bidirectional one to one mapping, so it is important to call the setters of both EmployeeEntity and AddressEntity to set each other during update. for example:

employeeEntity.setAddressEntity(addressEntity) and addressEntity.setEmpoyeeEntity(empoyeeEntity) has to explicitly called.

setting alone employeeEntity.setAddressEntity(addressEntity) will not work.

Answer 2

• Always use integer Id and use .getSession.saveOrUpdate(entity); for save or update.

• In the One to One Mapping you should mention constrained=true on the child. It makes Child Id the same as Parent Id.

• Use these lines for child id. I don't know Java attributes syntax.

<generator class="foreign">
    <param name="property">employeeEntity</param>
</generator>

• Also remove Fetch type and Cascade.All from child. I think the default fetch mode is Select which is fine. Cascade is usally used for the Parent part which is responsible for the parent-child relation.