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 discusses AEROGEAR-795 which 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, page and perPage. 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 the next link:

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}

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

Reference:

• Paging Support in AeroGear Controller

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