web service integration, REST API, retrofit

1. Web Service Integration
Anuchit Chalothorn
anoochit@gmail.com

2. REST API
A RESTful API takes advantage of HTTP methodologies.
● GET to retrieve a resource
● PUT to change the state of or update a resource, which
can be an object, file or block
● POST to create that resource
● DELETE to remove it.

3. Request method example
● GET /person → list person
● GET /person/id → list person with given id
● POST /person → create new person
● PUT /person/id → edit or update person with given id
● DELETE /person/id → delete person with given id

4. JSON
JSON (JavaScript Object Notation) is a lightweight
data-interchange format. It is easy for humans to read and
write.

5. JSON Structure
● A collection of name/value pairs. In various languages,
this is realized as an object, record, struct, dictionary,
hash table, keyed list, or associative array.
● An ordered list of values. In most languages, this is
realized as an array, vector, list, or sequence.

9. Retrofit API Client
retrofit= new Retrofit.Builder()
.baseUrl("http://api.example.com/")
.addConverterFactory(GsonConverterFactory.create())
.build();

10. Retrofit API Interface
public interface ApiInterface {
@GET("place")
Call<List<Person>> doGetPlaceList();
}
Note: request url → http://api.example.com/place

11. // Api call
ApiInterface apiInterface = ApiClient.getClient().create(ApiInterface.class);
Call<List<Place>> call = apiInterface.doGetPlaceList();
call.enqueue(new Callback<List<Place>>() {
@Override
public void onResponse(Call<List<Place>> call, Response<List<Place>> response) {
int statusCode = response.code();
Log.d("TAG", "code = " + statusCode);
List<Place> place = response.body();
adapter = new PlaceAdapter(place);
recyclerView.setAdapter(adapter);
}
@Override
public void onFailure(Call<List<Place>> call, Throwable t) {
Log.d("TAG", "" + t.getMessage());
}
});
API Call

12. Picasso
Picasso.with(context)
.load(image_url)
.error(R.drawable.placeholder_error)
.placeholder(R.drawable.placeholder)
.into(imageview);

13. Build.gradle
compile 'com.google.code.gson:gson:2.8.0'
compile 'com.squareup.retrofit2:retrofit:2.2.0'
compile 'com.squareup.retrofit2:converter-gson:2.2.0'
compile 'com.squareup.picasso:picasso:2.5.2'

14. Tools
● Advance REST Client
● JSONView
● jsonlint.com
● jsonschema2pojo.org

15. Codelab: Get data from JSON url
JSON url
https://raw.githubusercontent.com/anoochit/j
sondata/master/data02.json

16. Codelab: Get data from REST API
REST API
https://warm-ridge-87805.herokuapp.com/place