Java libraries supported - ronreynolds/openapi-generator GitHub Wiki
the JavaClientCodegen class of the openapi-generator project currently (2025-02-15) supports the use of 15 different HTTP-handling libraries, some that require a specific JSON-processing library and some that don't. a few other Java client libraries are supported by entirely different Codegen classes (JavaCXFClient, JavaHelidonClient, JavaHelidonCommon, JavaMicronaut (now deprecated), etc) which are beyond the scope of this wiki for now.
the purpose of this wiki is to document the basics of the libraries supported by JavaClientCodegen and to start to plan a way to make them more consistent with each other. all of this is based on the code (mustache files and generated sample java) and not the published docs. the number of mustache files for a specific library seems a reasonable start for a complexity metric.
The libraries
based on:
modules/openapi-generator/src/main/resources/Java/librariesorg.openapitools.codegen.languages.AbstractJavaCodegenorg.openapitools.codegen.languages.JavaClientCodegen
| HTTP library | JSON library options | Notes |
|---|---|---|
| apache-httpclient | Jackson | 7 mustaches; ApiClient extends JavaTimeFormatter |
| feign | GSON or Jackson | 14 mustaches + auth and model dir; no JavaTimeFormatter |
| google-api-client | Jackson | 6 mustaches; no JavaTimeFormatter |
| jersey2 | Jackson | 20 mustaches + auth dir; ApiClient extends JavaTimeFormatter |
| jersey3 | Jackson | 21 mustaches + auth dir; ApiClient extends JavaTimeFormatter |
| microprofile | Jackson or JSON-B | 35 mustaches; no ApiClient at all |
| native | GSON or Jackson (tho only Jackson is listed in pom) | Java-11+; 23 mustaches; no JavaTimeFormatter |
| okhttp-gson | GSON | 24 mustaches + auth dir; no JavaTimeFormatter |
| rest-assured | GSON or Jackson | Java-8 only; 12 mustaches; no JavaTimeFormatter |
| restclient | Jackson | 6 mustaches + auth dir; ApiClient extends JavaTimeFormatter |
| resteasy | Jackson | 6 mustaches; ApiClient extends JavaTimeFormatter |
| resttemplate | Jackson | 9 mustaches; ApiClient extends JavaTimeFormatter |
| retrofit2 | GSON or Jackson (play24/25/26 seem to dictate Jackson) | 15 mustaches + auth, play24, play25, play26, play-common.auth dir; no JavaTimeFormatter |
| vertx | Jackson | 9 mustaches + auth dir; ApiClient extends JavaTimeFormatter |
| webclient | Jackson | 8 mustaches + auth dir; ApiClient extends JavaTimeFormatter |