Allow creation of UriTemplates when pointing to controller methods.

[Gotusso]

Would be nice to have an easy way of return URL templates directly. For instance, suppose we have a method like

@RequestMapping
public HttpEntity<ListResource> list(
        @RequestParam(value = "query", required = false) String query,
        @RequestParam(value = "page", defaultValue = "1") Integer page,
        @RequestParam(value = "limit", defaultValue = "10") Integer limit) {
    // ...
}

I can reference an specific invocation with linkTo(methodOn(Controller.class).list("foo", 1, 20) but I think there is no easy way to reference a generic call without specifing the method parameters. Invoking with null results in a exception.

I would like to get something like

{
    rel: "list"
    href: "http://localhost:8080/myresource{?query,page,limit}"
}

Is that possible?
Regards

[steventhomson]

It is possible. You should use PagedResources.

For Example:

@RequestMapping(method = RequestMethod.GET)
public HttpEntity<PagedResources<Resource<?>>> viewResources(Pageable pageable, PagedResourcesAssembler<?> assembler)
{
    ...
    // query your repository
    List<?> resources = ... 
    ...

    return new ResponseEntity<PagedResources<Resource<?>>>(assembler.toResource(new PageImpl<?>(
        resources,
        pageable,
        resources.size())), HttpStatus.OK);
}

? is whatever resource class you are querying.

The response should be like this:

{
    "links": [
        {
            "rel": "self",
            "href": "/rest/resources{?page,size,sort}"
        }
    ],
    "content": [
        ...
    ],
    "page": {
        "size": 20,
        "totalElements": 10,
        "totalPages": 1,
        "number": 0
    }
}

[Gotusso]

The key of your example seems to be PagedResourcesAssembler, as it's the responsible for build the link. However, this process looks a bit cumbersome for me, and would be nice to have a simpler method, and generic enough to add it to any resource, not just lists.

[ksokol]

ControllerLinkBuilder has all ingredients it needs to build a template url. What is missing is a convenience method for this:

Link link = ControllerLinkBuilder.linkTo(methodOn(YourController.class).yourMethod(...).withRel("yourRel");
DummyInvocationUtils.LastInvocationAware invocations = (DummyInvocationUtils.LastInvocationAware) ControllerLinkBuilder.methodOn(YourController.class).yourMethod(...);
DummyInvocationUtils.MethodInvocation invocation = invocations.getLastInvocation();
Method method = invocation.getMethod();

MappingDiscoverer discoverer = new AnnotationMappingDiscoverer(RequestMapping.class); //taken from ControllerLinkBuilder
String mapping = discoverer.getMapping(YourController.class, method);

UriTemplate uriTemplate = new UriTemplate(mapping);
List<TemplateVariable> variables = link.getVariables();
//the templated link
Link templatedLink = new Link(uriTemplate.with(new TemplateVariables(variables)), link.getRel());

[dschulten]

A possible workaround in getByXXX scenarios is a class-level RequestMapping such as @RequestMapping("/events") on an EventController. The 'default handler method' which returns events needs a no-value @RequestMapping annotation to make this work, and the method that returns single items by XXX must simply add the parameter to the path defined on class-level, like @RequestMapping("/id") .

@Controller
@RequestMapping("/events")
public class EventController {

    // 'default' handler
    @RequestMapping
    public @ResponseBody Resources<Resource<Event>> getEvents() {
    }

    @RequestMapping("/{id}") 
    public @ResponseBody Resource<Event> getEventById(@PathVariable int id) {
    }
    ...

Now, to point to getEventById with a templated URL you can say somewhere else:

new Link(linkTo(EventController.class).toString() + "{/eventId}", "event") 

resulting in a templated link likehttp://localhost/events{/eventId}

[jiwhiz]

I have a similar issue, but a little tricky. My PublicBlogRestController has a method to get blog comment by ID:

    @RequestMapping(method = RequestMethod.GET, value = "/public/blogs/{blogId}/comments/{commentId}")
    public HttpEntity<PublicCommentResource> getBlogApprovedCommentPostById(
            @PathVariable("blogId") String blogId,
            @PathVariable("commentId") String commentId) {
...
    }

I want my PublicBlogResource will have a templated link to its comment, like "/public/blogs/blog123/comments/{commentId}".

Maybe UriTemplate class can partially expand the template with path parameter values, like setPathParameter(String, Object), so I can create link like this:

Link commentLink = new Link(
    new UriTemplate(baseUri+"/public/blogs/{blogId}/comments/{commentId}").setPathParameter("blogId", blog.getId()), 
    "comment");
        resource.add(commentLink);

Does it make sense? Or any other options?