Spring Data REST @Idclass not recognized

Question

I have an entity named EmployeeDepartment as below

@IdClass(EmployeeDepartmentPK.class) //EmployeeDepartmentPK is a serializeable object
@Entity
EmployeeDepartment{

@Id
private String employeeID;

@Id
private String departmentCode;
---- Getters, Setters and other props/columns
}

and I have a Spring Data Repository defined as as below

@RepositoryRestResource(....)
public interface IEmployeeDepartmentRepository extends PagingAndSortingRepository<EmployeeDepartment, EmployeeDepartmentPK> {

}

Further, I have a converter registered to convert from String to EmployeeDepartmentPK.

Now, for an entity, qualified by ID employeeID="abc123" and departmentCode="JBG", I expect the ID to use when SDR interface is called is abc123_JBG. For example http://localhost/EmployeeDepartment/abc123_JBG should fetch me the result and indeed it does.

But, when I try to save an entity using PUT, the ID property available in BasicPersistentEntity class of Spring Data Commons is having a value of abc123_JBG for departmentCode. This is wrong. I'm not sure if this is an expected behaviour.

Please help.

Thanks!

Answer 1

Currently Spring Data REST only supports compound keys that are represented as by a single field. That effectively means only @EmbeddedId is supported. I've filed DATAJPA-770 to fix that.

If you can switch to @EmbeddedId you still need to teach Spring Data REST the way you'd like to represent your complex identifier in the URI and how to transform the path segment back into an instance of your id type. To achieve that, implement a BackendIdConverter and register it as Spring bean.

@Component
class CustomBackendIdConverter implements BackendIdConverter {

  @Override
  public Serializable fromRequestId(String id, Class<?> entityType) {

    // Make sure you validate the input

    String[] parts = id.split("_");
    return new YourEmbeddedIdType(parts[0], parts[1]);
  }

  @Override
  public String toRequestId(Serializable source, Class<?> entityType) {

    YourIdType id = (YourIdType) source;
    return String.format("%s_%s", …);
  }

  @Override
  public boolean supports(Class<?> type) {
    return YourDomainType.class.equals(type);
  }
}

Answer 2

If you can't use @EmbeddedId, you can still use @IdClass. For that, you need the BackendIdConverter as Oliver Gierke answered, but you also need to add a Lookup for your domain type:

@Configuration
public class IdClassAllowingConfig extends RepositoryRestConfigurerAdapter {

@Override
public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
    config.withEntityLookup().forRepository(EmployeeDepartmentRepository.class, (EmployeeDepartment ed) -> {
        EmployeeDepartmentPK pk = new EmployeeDepartmentPK();
        pk.setDepartmentId(ed.getDepartmentId());
        pk.setEmployeeId(ed.getEmployeeId());
        return pk;
    }, EmployeeDepartmentRepository::findOne);
}

}