With the current gitlab4j-api (4.19.0), when the jersey-media-json-binding is on the classpath, jersey will use jsonb (eclipse yasson) to deserialize the json response, because it implements the ForcedAutoDiscoverable interface and always gets registered with a higher priority.

https://github.com/eclipse-ee4j/jersey/blob/master/media/json-binding/src/main/java/org/glassfish/jersey/jsonb/internal/JsonBindingAutoDiscoverable.java

https://github.com/eclipse-ee4j/jersey/blob/9dbc693eaff403e4a1b285cac77361fd96b9b694/core-common/src/main/java/org/glassfish/jersey/internal/spi/ForcedAutoDiscoverable.java

To fix this, we need to register the JacksonFeature to force jersey to use jackson over json binding.

Context:

I use 2 plugins in jenkins: the gitlab-plugin which uses jersey directly and the gitlab-branch-source plugin that uses gitlab4j-api (packaged in the gitlab-api plugin).

Since gitlab-plugin has been updated to use a new jersey2-api plugin, I had strange ClassCastException with gitlab4j-api and jersey, to fix this I'm modifying the gitlab-api plugin to also use the jersey2-api plugin instead of packaging its own jersey libs. Because the jersey2-api plugin contains jersey-media-json-binding, it wasn't working until I made the changes to register JacksonFeature.