In order to execute REST calls in Java, one needs to generate the bindings first. There are several ways to get those: . The most tedious one is to do that manually: one needs to carefully get hold of all possible JSON request and response combinations, develop the corresponding Java objects, choose the JSON serialization framework, as well as the HTTP client. . The next best option is to use proprietary code generators such as Swagger or Apiary. This requires the API provider to provide the model in one of the possible formats. On the downside, one needs to use the relevant tool. Sometimes, the format is more or less open, such as the OpenAPI specification. In that case, the tool can be chosen among those that implement the format. . In the best of cases, the bindings are already provided.