How to dynamically remove fields from a json response?

Question

I'm using spring to create a restful api, so far so good, my question is how to model the fields that go to the response dynamically?

Thats the controller that i'm using:

@Controller

public class AlbumController {

@Autowired
private MusicService musicService;

@RequestMapping(value = "/albums", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public Collection<Resource<Album>> getAllAlbums() {

    Collection<Album> albums = musicService.getAllAlbums();
    List<Resource<Album>> resources = new ArrayList<Resource<Album>>();
    for (Album album : albums) {
        resources.add(this.getAlbumResource(album));
    }
    return resources;

}

@RequestMapping(value = "/album/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public Resource<Album> getAlbum(@PathVariable(value = "id") String id) {

    Album album = musicService.getAlbum(id);
    return getAlbumResource(album);

}

private Resource<Album> getAlbumResource(Album album) {

    Resource<Album> resource = new Resource<Album>(album);


    // Link to Album
    resource.add(linkTo(methodOn(AlbumController.class).getAlbum(album.getId())).withSelfRel());
    // Link to Artist
    resource.add(linkTo(methodOn(ArtistController.class).getArtist(album.getArtist().getId())).withRel("artist"));
    // Option to purchase Album
    if (album.getStockLevel() > 0) {
        resource.add(linkTo(methodOn(AlbumController.class).purchaseAlbum(album.getId())).withRel("album.purchase"));
    }

    return resource;

}

@RequestMapping(value = "/album/purchase/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public Resource<Album> purchaseAlbum(@PathVariable(value = "id") String id) {

    Album a = musicService.getAlbum(id);
    a.setStockLevel(a.getStockLevel() - 1);
    Resource<Album> resource = new Resource<Album>(a);
    resource.add(linkTo(methodOn(AlbumController.class).getAlbum(id)).withSelfRel());
    return resource;

}
}

And the model:

public class Album {

private final String id;
private final String title;
private final Artist artist;
private int stockLevel;

public Album(final String id, final String title, final Artist artist, int stockLevel) {
    this.id = id;
    this.title = title;
    this.artist = artist;
    this.stockLevel = stockLevel;
}

public String getId() {
    return id;
}

public String getTitle() {
    return title;
}

public Artist getArtist() {
    return artist;
}

public int getStockLevel() {
    return stockLevel;
}

public void setStockLevel(int stockLevel) {
    this.stockLevel = stockLevel;
}
}

Answer 1

I'm struggling with this requirement, too.

The following code is a workaround using the JsonViews already mentioned by @beerbajay in the comment to your question:

http://wiki.fasterxml.com/JacksonJsonViews

I'm using Spring Boot 1.2.3.

Views.java

package demo;

public class Views {

    static interface Public {}

    static interface Internal extends Public {}
}

Album.java

package demo;

import com.fasterxml.jackson.annotation.JsonView;

public class Album {

    @JsonView(Views.Public.class)
    private String id;

    @JsonView(Views.Public.class)
    private String title;

    @JsonView(Views.Public.class)
    private String artist;

    @JsonView(Views.Internal.class)
    private String secret;

    public Album(String id, String title, String artist, String secret) {
        this.id = id;
        this.title = title;
        this.artist = artist;
        this.secret = secret;
    }

}

AlbumController.java

package demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;

@RestController
public class AlbumController {

    @Autowired
    ObjectMapper mapper;

    @RequestMapping(value = "/album", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    public String getAlbum() throws JsonProcessingException {
        Album foo = new Album("1", "foo", "John Doe", "secretProperty");

        // replace the following value with runtime logic of your choice,
        // e.g. role of a user
        boolean forInternal = false;

        ObjectWriter viewWriter;
        if (forInternal) {
            viewWriter = mapper.writerWithView(Views.Internal.class);
        } else {
            viewWriter = mapper.writerWithView(Views.Public.class);
        }

        return viewWriter.writeValueAsString(foo);
    }
}

So the key is to use jackson's ObjectMapper and ObjectWriter to generate a string of the json representation of your object.

Feels kind of ugly to me, but works. Certainly the question remains how this scales when defining more than one RequestMapping.