如何在不同资源中重用REST方法？

Question

Hi,

I am building a REST-api using Jersey and Java. I wonder if it is possible to reuse a method in many resources.

As an example If I have this code:

@Path("/users")
public class UserResource {
    @GET
    @Path("/{uid}/comments")
    @Produces(MediaType.APPLICATION_JSON)
    public List<Comment> getComments() {
        return commentService.getOnEntity("User", uid);
    }   
}

and this:

@Path("/items")
public class ItemResource {
    @GET
    @Path("/{uid}/comments")
    @Produces(MediaType.APPLICATION_JSON)
    public List<Comment> getComments() {
        return commentService.getOnEntity("Item", uid);
    }   
}

Is it possible to reuse the code for specifying the method "/{uid}/comments/" so I do not need to write it in every resource that is going to need it?

I guess I could extend a CommentResource with the method, but the I can only add one set of methods. If I use Interface I could specify more than one set of methods but would have to rewrite the code inside the methods in every resource.

Edit After a tips from @thomas.mc.work I rewrote my code using a sub resource. It is better than the first solution since I get all methods from my sub resource and it only takes 4 lines of code per resource. This is how it looks like:

@Path("/users")
public class UserResource {

    @Path("/{uid}/comments")
    public CommentSubResource getCommentSubResource(@PathParam("uid") String uid) {
        return new CommentSubResource("User", uid);
    }   
}

and this:

@Path("/items")
public class ItemResource {

    @Path("/{uid}/comments")
    public CommentSubResource getCommentSubResource(@PathParam("uid") String uid) {
        return new CommentSubResource("Item", uid);
    }   
}

and this:

public class CommentSubResource {

    private String entity;
    private String entityUid;

    public CommentSubResource(String entity, String entityUid) {
        this.entity = entity;
        this.entityUid = entityUid;
    }

    @GET
    @Path("/")
    @Produces(MediaType.APPLICATION_JSON)
    public List<Comment> getComments() {
        return commentService.getOnEntity(entity, entityUid);
    }

    @DELETE
    @Path("/")
    @Produces(MediaType.APPLICATION_JSON)
    public List<Comment> deleteComment(@PathParam("uid") String uid) {
        return commentService.delete(uid);
    }
}

This is much better. I have an idea to use java 8 and default implementation interfaces to be able to just implmenet an interface to get the functionality, but I am not sure if I am able to determine which resource the default implemented method is called from.

Edit
After some laboration I think subresources is the way to go, even if it´s not (according to me) the perfect solution.

Answer 1

There is a similar feature called "Subresource Locators" . You can decide in runtime which Resource is selected to process the request that is matching your JAX-RS method.