Freviously, I blogged about how to implement and document REST APIs in JavaEE applications with Eclipse MicroProfile. In this article, I describe the inverse scenario — how services can invoke other services via REST APIs over HTTP.
MicroProfile comes with a REST Client which defines a type-safe client programming model. The REST Client makes it easier to convert between the JSON data and Java objects in both directions.
There is pretty good documentation about the REST Client available (see below). In this article, I describe how I’ve used the client in my sample application. The application has a Web API service which implements the BFF (backend for front-end pattern). The Web API service uses the REST Client to invoke another ‘Authors’ service.
Get the code of the cloud-native starter application.
First, you need to define the interface of the service you want to invoke.
getAuthor method returns an object of the Authorclass.
The actual invocation of the authors service happens in AuthorsServiceDataAccess.java. The RestClientBuilder is used to get an implementation of the
AuthorsService interface. The deserialization of the data into a Java object is done automatically.
In order to use the RESTClientBuilder, you need to understand the concept of the ResponseExceptionMapper. This mapper is used to translate certain HTTP response error codes back into Java exceptions.
Read the following resources to learn more about the MicroProfile REST Client.