Working with ngResource services?

[rvillars]

Your projects seems promising but I have some difficulties with the documentation. You write:

Now you are able to instantiate the SpringDataRestAdapter object and process a given response:

var processedResponse = new SpringDataRestAdapter(response);

What is the 'response'? Do I have to get it "manually" with $http? What about ngResource that is used by angular-spring-data-rest itself?

Normally with ngResource you can create and use a resource service like this:

myApp.factory('Category', function ($resource) {
    return $resource('category/:categoryId', {categoryId: '@id'});
}

$scope.categories = Category.query(); // in the controller

How can I use angular-spring-data-rest this way to also make use of all ngResource convenience functions like 'get' or 'save'?

[guylabs]

The SpringDataRestAdapter processes the specified response and adds two new properties to the JSON structure; namely the _resources and the _embeddedItems property (these are configurable). With these two properties you are able to easily navigate to linked resources or to iterate over the embedded items.

And the _resources property wraps the Angular $resource method per default (is also configurable) such that you will get a $resource object returned which already has the correct endpoint set. For example you have the following JSON response from the Spring Data REST backend:

{
    "_links": {
        "self": {
            "href": "http://localhost:8080/categories{?page,size,sort}",
            "templated": true
        }
    },
...

Then when you call _resources method with the "self"parameter you will get the same as you would call the $resources method from Angular itself with the specified URL.

// response is the above response in JSON
var processedResponse = new SpringDataRestAdapter(response);

var resources = processedResponse._resources("self");
var angularResource = $resource('http://localhost:8080/categories');

// resources is the same configured object as the angularResource

I hope its more clear now and please tell me if I can then close the issue.

[rvillars]

Thx, for the clarification. Unfortunately this doesn't help me yet.

One of the common approaches of how to use $resource is the "Active Record" pattern (e.g. see here). A $resource is given an templated URL and it returns a constructor function that allows to query, save and create new resource instances. This $resource call is normally wrapped in a service so it looks like this:

myApp.factory('Category', function ($resource) {
    return $resource('category/:categoryId', {categoryId: '@id'}); // templated url
}

I can't see how I can achieve the same functionality with help of SpringDataRestAdapter. I tried it like this:

myApp.factory('Category', function (SpringDataRestAdapter, $http) {
    $http.get('http://localhost:8080').success(function(response) {
        var processedResponse = new SpringDataRestAdapter(response);
        var resources = processedResponse._resources('category/:categoryId', {categoryId: '@id'});
        return resources;
    });
});

But unfortunately _resources doesn't seem to work with a templated URL and calling Category.query(); fails because of course the $http.get call is deferred and too late for the controller.

So, my question is: How do I have to implement the resource service function 'Category' so I have the same functionality as if i would with $resource?

If you would have a look at my code you will find it here https://github.com/rvillars/bookapp-hateoas

[guylabs]

Ok now I see your point. You are able to exchange the call to the backend inside SpringDataRestAdapter by adding the resourcesFunction to the config object. Please read the documentation about this here.

The default underlying method is using the Angular $resource method in the following way:

return $injector.get("$resource")(url, paramDefaults, actions, options);

And this is what you get when you call the _resources function on the processed response.

In short: If you want to add this kind of parameterized URL then you need to exchange the underlying call to the backend like it's described above.

But one question I do have: Why do you want to have a parameterized URL? Because the HATEOAS responses defined all the links which are needed to get all the resources and the default Spring Data REST responses do not have any id's in the entity representation, just the self link.

[rvillars]

Thx for your patience :-). The parameterized URL isn't the real problem I have. My problem is, that there already needs to be a response to define a new SpringDataRestAdapter. Please have a look at the following (pretty common) AngularJS code example:

myApp.controller('CategoryController', function ($scope, Category) {
    $scope.categories= Category.query(); // this works because 'Category' is already fully processed
}
myApp.factory('Category', function ($resource) {
    return $resource('http://localhost:8080/categories'});
});

And now the same example with a SpringDataRestAdapter

myApp.controller('CategoryController', function ($scope, Category) {
    $scope.categories= Category.query(); // does not work (at this moment) because 'Category' is still waiting for $http.get. -> error
}
myApp.factory('Category', function (SpringDataRestAdapter, $http) {
    $http.get('http://localhost:8080').success(function(response) {
        var processedResponse = new SpringDataRestAdapter(response);
        var resources = processedResponse._resources('categories'});
        return resources;
    });
});

As you can see, in the first example the 'Category' service is fully asynchronous and therefore the controller can be initialized without error.
In the second example the 'Category' service waits for the $http response (as it is needed for the SpringDataRestAdapter and the _resources call) and therefor the service isn't ready when the controller want's to call it. -> error.

I'm sure there is some defer/promise magic to get this working fully asynchronous. But unfortunately I didn't got it working. I'd would be nice to have some Helper functions in your framework to create a SpringDataRest resource asynchronously as the whole promise concept is not easy to understand (not just for me ;-) ).

I know the examples look a bit constructed at first. But the the active record pattern is used in a lot of AngularJS examples and tutorials out there. And perhaps it would help people to have at least an example of how to integrate angular-spring-data-rest into that pattern.

[guylabs]

Hi Roger,

sorry for the late response but I have good news for you ;). I added the ability to pass a promise as data object to the SpringDataRestAdapter. Please see this on how to do this.

I also had a look at your bookapp-hateoas project and currently it is not possible to use the SpringDataRestAdapter similar to the ´$resource´ object from Angular, because the methods like query(), save() etc. are not defined in the processed response. I implemented it with the new promise functionality and it worked as I described it in the documentation.

But you are able to create your own $resource object as it is written in the chapter "Custom REST adapters with $http" on page 101 in this PDF.

May you please have a look at the promise functionality and if it fits your needs and mabye give me feedback?

I hope this helps :).

[rvillars]

The new promise function is very helpful. And also your example project (https://github.com/guylabs/angular-spring-data-rest-sample) was a helpful starting point. Thx! I was now able to adapt the framework for my project (going to check in the code soon).

If someone is interested in using angular-spring-data-rest with a active record pattern approach, there is a quite interesting example at http://g00glen00b.be/spring-data-angular.

[guylabs]

Nice! And a very interesting approach in the blog post. Thanks for sharing it.

[ziftytodd]

I have to agree with Roger, the documentation is great on what to do ONCE you have a response to process. But it's totally unclear (at first) how you're supposed to get that response. I think most people are coming to this project from https://github.com/jmarquis/angular-hateoas where you can just drop it in and it enhances the functionality of the $resource, whereas this project doesn't appear to do that at all.

From what I can gather, from the sample project in rvillars comment (which was very helpful), you have to pretty much write your own custom resource, which seems overkill if you're using the standard spring data rest repository to expose an API. Not sure why implementing the same functionality of $resource, with ability to override, wouldn't make sense. It would cut out a lot of boilerplate for simple collections.

At the very least, please consider adding more documentation to this project showing the full code for the basic CRUD operations, including making the request, or linking to the sample project.

Also, the documentation refers to SpringDataRestAdapter.processWithPromise(promise), but that appears to not be a valid method name and it works just fine with just SpringDataRestAdapter.process(promise).

[guylabs]

Hi @ziftytodd,

thanks for your opinion and I try to add more documentation about how to get the response. The link to the sample project is already there: https://github.com/guylabs/angular-spring-data-rest#see-how-it-works (even before the TOC ;))

And thanks for spotting the issue with the processWithPromise method. I will fix it asap.

Thanks and regards,

Guy