Sub-Resources with Jersey,Spring, jax-rs

A simple example on how to use Sub-Resources with Jersey and Spring.

For the sake of discussion, consider a Resource /orders. One would typically POST to the resource to create an Order, update the Order at the Resource /orders/{id}, GET the Resource from the URI /orders/{id} and also delete the order at the Resource /orders/{id}.

One can therefore state that /orders/{id} is a Sub-Resource of /orders.

In jax-rs, sub-resources are obtained from the parent resource. A parent resource will not define a HTTP method for the sub-resource, but instead simple have a @Path annotation indicating a sub-resource.

For example,

---

@Path("/orders")
@Component

@Scope("singleton")
public class OrdersResource {
@Context

private ResourceContext resourceContext;

@Path("/{id}")
public OrderResource subResource(@PathParam("id") String id) {

  OrderResource resource = resourceContext.getResource(OrderResource.class);

  resource.setOrderId(Long.parseLong(id));

  return resource;

}
...
}

---

In the above example, we have an OrdersResource that services the URI pattern of /orders. Calls to /orders/{id} are delegated to a sub-resource of the OrdersResource called OrderResource as shown below:

---

@PerRequest
@Component
@Scope("prototype")

public class OrderResource {
private Long orderId;
// Jersey injected

@Context
private ResourceContext resourceContext;

// Spring injected
@Autowired

private OrderService orderService;
@Autowired
private MapperIF beanMapper;

....
public void setOrderId(Long orderId) {
  this.orderId = orderId;

}

// @Context are Jersey injected

@GET
@Produces("application/xml")

public Response getOrder(@Context HttpHeaders hh,
    @Context Request request)    { ... }

@Consumes("application/xml")
@PUT
public void updateOrder(@PathParam("id") String id, OrderDto orderDto) {

 ....
}

@DELETE
public void deleteOrder(@PathParam("id") String id) {

  ....
}

@Path("/lineItems")
public LineItemListDto getLineItems() throws OrderNotFoundException {

 .....
}
}

---

Both the above mentioned Resources are beautifully managed by Spring and Jersey interoperability. Jersey Resources are injected by Jersey and Spring resources are injected by Spring auto-wiring. So cool!!!!

As shown above the OrderResource is following a Prototype pattern and is obtained via a called to resourceContext.getResource(OrderResource.class).

I quite like the fact that the OrderResource is declared as sub-resource of the OrdersResource and the creation of the Sub-Resource via the prototype pattern matches so beautifully within jax-rs. It becomes a trivial exercise to trace the flow of a uri-call from the parent resource to sub-resources.