PayPal HttpClient

PaypalHttp is a generic HTTP Client.

In it's simplest form, an HttpClient exposes an #execute method which takes an HttpRequest, executes it against the domain described in an Environment, and returns an HttpResponse. It throws an IOException if anything goes wrong during execution.

Environment

An Environment describes a domain that hosts a REST API, against which an HttpClient will make requests. Environment is a simple interface that wraps one method, #baseUrl.

Environment env = () -> "https://example.com";

Requests

HttpRequests contain all the information needed to make an HTTP request against the REST API. Specifically, one request describes a path, a verb, any path/query/form parameters, headers, attached files for upload, and body data. This class also holds a reference to the type of the response for deserializtion, if a structured response is expected.

Responses

HttpResponses contain information returned by a server in response to a request as described above. They contain a status code, headers, and any data returned by the server, deserialized in accordance with the type in the HttpRequest from which this reponse originated.

HttpRequest<MyResponsePojo> req = new HttpRequest("/path/to/resource", "GET", MyResponsePojo.class);

HttpResponse<MyResponsePojo> resp = client.execute(req);

Integer statusCode = resp.statusCode();
Headers headers = resp.headers();
MyResponsePojo responseData = resp.result();

Injectors

Injectors wrap closures that can be used for executing arbitrary pre-flight logic, such as modifying a request or logging data. Injectors are attached to an HttpClient using the #addInjector method.

The HttpClient executes its Injectors in a first-in, first-out order, before each request.

HttpClient client = new HttpClient(env);

client.addInjector(req -> {
  log.log(req);
});

client.addInjector(req -> {
  req.headers().header("Request-Id", "abcd");
});

...

Error Handling

HttpClient#execute may throw an IOException if something went wrong during the course of execution. If the server returned a non-200 response, this execption will be an instance of HttpException that will contain a status code and headers you can use for debugging.

try {
  HttpResponse<MyResponsePojo> resp = client.execute(req);
} catch(IOException ioe) {
  if (ioe instanceof HttpException) {
    // Inspect this exception for details
    HttpException he = (HttpException) ioe;
    int statusCode = ioe.statusCode();
  } else {
    // Something else went wrong
  }
}

Serializer

(De)Serialization of request and response data is done by implementations of the Serializer interface. PaypalHttp currently supports json encoding out of the box.

SSL

By default, PaypalHttp will use the built-in TLSSoccketFactory when connecting to URLs that use https as their scheme. If you'd like to do cert-pinning, or use a different SSL implementation, you can provide your own SSLSocketFactory via HttpClient#setSSLSocketFactory().

License

PaypalHttp-Java is open source and available under the MIT license. See the LICENSE file for more info.

Contributions

Pull requests and new issues are welcome. See CONTRIBUTING.md for details.