Summers brought up a good point today on IRC which I've forgot to mention. We've said that it will be possible to pass the page parameters as HTTP Headers and this is still the plan. But the demo is using the lastest from upstream and support for passing headers to the client is not there yet. I hope to have this working shortly though and I'll post back with information as soon as possible, tomorrow or Monday at the latest.




On 10 January 2013 15:32, Daniel Bevenius <daniel.bevenius@gmail.com> wrote:
>I know it's just a demo but I think making that JSON format consistent so that the car data is always in an array under the "cars" key would be better.
Good point. I'll change this so that there is always a "cars' key.


On 10 January 2013 15:13, Kris Borchers <kris@redhat.com> wrote:

On Jan 10, 2013, at 3:02 AM, Daniel Bevenius <daniel.bevenius@gmail.com> wrote:

We talked about paging yesterday on IRC, and it was decided to add a paging example to aerogear-controller-demo. What follows is an example to kick of further discussion about what the example should look like.

AeroGear Controller Demo Paging Route

This page discussesAEROGEAR-795which is about adding an example to aerogear-controller-demo to demonstrate paging support so that the client libraries (Android, JavaScript, and iOS) can be tested against it.

This is only a suggestion and the implementation and the names of the query parameters can all be changed.

Use case

The example is using cars as the resource to interact with. To be able to query we need something to query, so lets start by adding some cars by posting.

Adding Cars

URL="http://controllerdemo-danbev.rhcloud.com/aerogear-controller-demo"

curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Black&car.brand=BMW" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Red&car.brand=Ferrari" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Blue&car.brand=Skoda" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Green&car.brand=Audi" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Yello&car.brand=Opel" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Pink&car.brand=Mini" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Gray&car.brand=Nissan" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Red&car.brand=Volvo" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Blue&car.brand=Saab" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Black&car.brand=Mazda" -X POST "$URL/cars"
curl -i --header "Accept: application/json" -H "Content-type: application/x-www-form-urlencoded" --data "car.color=Yello&car.brand=Golf" -X POST "$URL/cars"

The example uses an in-memory database so the data will be cleared upon redployment/restart of the server. So you only need to populate/post when you've restared or redployed.

With the cars in place, we can now issue GET requests with paging query parameters. The following route has been added to the demo:

route()
      .from("/cars")
      .on(RequestMethod.GET)
      .produces(MediaType.JSON.toString())
      .to(Cars.class).get(param("page", "0"), param("perPage", "-1"));

From this we can see that there are two optional parameters,pageandperPage. If these are not specified all cars will be returned.

Getting a page of Cars

URL="http://controllerdemo-danbev.rhcloud.com/aerogear-controller-demo"
curl -i --header "Accept: application/json" "$URL/cars?page=0&perPage=4"

The request will return:

{
  "metadata":{"page":0,"perPage":4},
  "cars":[
            {"color":"Black","brand":"BMW","id":1},
            {"color":"Red","brand":"Ferrari","id":2},
            {"color":"Blue","brand":"Skoda","id":3},
            {"color":"Green","brand":"Audi","id":4}
          ],
  "links":{
          "first":"cars?page=0&page=4",
          "previous":"cars?page=0&page=4",
          "next":"cars?page=1&page=4"
          }
}

Getting the next page of Cars

To get the next page you can follow thenextlink:

URL="http://controllerdemo-danbev.rhcloud.com/aerogear-controller-demo"
curl -i --header "Accept: application/json" "$URL/cars?page=1&perPage=4"
{
    "metadata":{"page":1,"perPage":4},
    "cars":[
            {"color":"Yello","brand":"Opel","id":5},
            {"color":"Pink","brand":"Mini","id":6},
            {"color":"Gray","brand":"Nissan","id":7},
            {"color":"Red","brand":"Volvo","id":8}
           ],
    "links":{
            "first":"cars?page=0&page=4",
            "previous":"cars?page=0&page=4",
            "next":"cars?page=2&page=4"
            }
}

Get all Cars

URL="http://controllerdemo-danbev.rhcloud.com/aerogear-controller-demo"
curl -i --header "Accept: application/json" "$URL/cars"

Get a single Car

URL="http://controllerdemo-danbev.rhcloud.com/aerogear-controller-demo"
curl -i --header "Accept: application/json" "$URL/cars/1"

The request will return:

{"color":"Black","brand":"BMW","id":1}

Hmmm, the data returned should be consistent, right? Whether paging parameters are supplied or not, the structure of the JSON to access the car info should be the same. It's fine to leave out the metadata and links when they're not needed I guess but to access the car info, currently you have:

Not Paged: {"color":"Black","brand":"BMW","id":1}
Paged: {"cars":[{"color":"Black","brand":"BMW","id":1},]}

I know it's just a demo but I think making that JSON format consistent so that the car data is always in an array under the "cars" key would be better.

Again, anything here can be changed, the name of the query parameters, the implementation, and what is returned.

Reference:

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