Spring Data Rest projection does not work for single resources

Question

I have the following projection written for an entity class.

@Projection(name = "instituteProjection", types = { Institute.class })
public interface InstituteProjection {

    String getOrganizationName();

    Address getRegisteredAddress();
}

Now I am trying to apply this projection whenever I call the url http://localhost:8080/institutes/1?projection=instituteProjection which returns a single institute resource. The controller GET method implementation is as follows:

@RequestMapping(value = "institutes/{instituteId}", method = RequestMethod.GET,
        produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<?> getInstitute(@PathVariable Long instituteId) {
    Institute institute = service.getInstitute(instituteId);
    return new ResponseEntity<>(institute, HttpStatus.OK);
}

The problem is this does not return the institute projection. It returns the default repository json.

The projection only works if I use the SDR generated controller instead of the custom rest controller I have implemented.

So how do I apply the projection in the custom controller?

UPDATE 1 Institute class

@Data
@Entity
public class Institute{

 private String organizationName;

    @OneToOne
    private Address registeredAddress;

    @OneToOne
    private Address mailingAddress;

}

UPDATE 2

Address class

    public class Address {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id")
    private long addressID;   

    @ManyToOne
    private Street street;

    @ManyToOne
    private Country country;

    private double latitude;

    private double longitude;

    @ManyToOne
    private City city;


}

Answer 1

It's very straightforward. You can use your existing projection, you could even remove the @Projection annotation, this one is not mandatory to get it working with custom controllers.

So the minimum projection would be:

public interface InstituteProjection {

    String getOrganizationName();

    Address getRegisteredAddress();

}

Now, to convert your Institute entity, you need an implementation of the ProjectionFactory interface, an existing one is SpelAwareProxyProjectionFactory.

To make a bean of that type accessible, add a small config:

@Configuration
public class ProjectionFactoryConfig {

    @Bean
    public ProjectionFactory projectionFactory() {
        return new SpelAwareProxyProjectionFactory();
    }

}

And now you can use it in your contoller to convert your Institute to your InstituteProjection:

@Autowired
private ProjectionFactory projectionFactory;

...

@RequestMapping(value = "institutes/{instituteId}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<?> getInstitute(@PathVariable Long instituteId) {
    final Institute institute = service.getInstitute(instituteId);
    final InstituteProjection instituteProjection = projectionFactory.createProjection(InstituteProjection.class, institute);
    return new ResponseEntity<>(instituteProjection, HttpStatus.OK);
}