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Translating API Endpoints into SDK Methods

Developers explore your API reference documentation to understand what endpoints and actions are available. The unique methods in your SDK enable developers to interact with API endpoints and perform those actions. We discussed naming conventions in the design section. Keep these in mind and the coding style of the language you are working in.

What goes into an endpoint method?

Should you put all methods in a single class and call it ApiClient. This has the advantage of reducing the number of classes developers need to initialize. The downside as the number of endpoints increase so will the class file size. At Xero, our ApiClient got so large that PHP developers needed to modify their IDE settings in order to open the large file and view the source code. We also heard from developers that it was difficult to navigate a single file with so many methods.

Grouping related methods in a class with an intuitive name may be a better choice. For example, getContact, listContacts and createContact, etc would go in a class named ContactsApi (or something like it). Organizing methods in this way also helps with code hinting. Developers initializing ContactsApi see a short list of available and highly relevant methods.

Below are components you’ll employ in a method depending on your API.

  • Validate argument(s)
  • Set header(s)
  • Construct URL with query parameters
  • Set HTTP verb
  • Serialize request body
  • Set Credentials (token, username/password)
  • Build and execute HTTPRequest
  • Deserialize response
  • Return response as native object

Let’s see how each bullet point translates into Java code. The code has been abbreviated in places and external classes are doing some of heavy lifting as you’ll want to move common code into reusable classes.

Method to create a new contact

public Contact createContact(Contact contact) throws IOException {


Validate required arguments

if (contact == null) {
throw new IllegalArgumentException(
"Missing the required parameter 'contact'");

Set relevant headers

(like user agent metadata)

HttpHeaders headers = new HttpHeaders();

Construct a URL

Include any query parameters that exist

UriBuilder uriBuilder = UriBuilder.fromUri({baseURL} + "/Contacts");

//handle query parameters with the following line of code
//uriBuilder = uriBuilder.queryParam(key, value);

String url =;
GenericUrl genericUrl = new GenericUrl(url);

//Serialize the contact model into JSON for our HTTP request

HttpContent content = JacksonJsonHttpContent(contact);

Set the access token

Credential credential =
new Credential(BearerToken.authorizationHeaderAccessMethod())


Build and execute HTTP request

HttpTransport transport = helperClass.getHttpTransport();
HttpRequestFactory requestFactory = transport.createRequestFactory(credential);
HttpResponse response = requestFactory
.buildRequest(HttpMethods.POST, genericUrl, content)

Deserialize JSON response

You'll want to return a Contacts model in this example.

TypeReference<Contacts> typeRef = new TypeReference<Contacts>() {};

return helperClass.getObjectMapper().readValue(response.getContent(), typeRef);

For more details go to the serialization section.

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