How to extract ObjectMapper from JAX-RS Client?

Question

I am using Jersey JAX-RS client (version 2.0). I know it is using a Jackson ObjectMapper to generate and parse JSON. I want to use that same object to generate JSON for some

Answer 1

Jersey does not actually explicitly configure an ObjectMapper instance, rather it delegates to JacksonJsonProvider, which in turn uses a default mapper instance. You can trace through the JacksonProviderProxy code to see how it works. You can create and customize a shared mapper to be used throughout your application by defining a context resolver:

@Provider
public class ObjectMapperContextResolver implements
        ContextResolver {
    private ObjectMapper mapper = null;

    public ObjectMapperContextResolver() {
        super();

        // Illustrate configuration of the mapper instance
        mapper = new ObjectMapper().configure(
                SerializationConfig.Feature.WRAP_ROOT_VALUE, true).configure(
                DeserializationConfig.Feature.UNWRAP_ROOT_VALUE, true);
    }

    @Override
    public ObjectMapper getContext(Class type) {
        return mapper;
    }
}

The Jackson provider will retrieve its mapper instance from this resolver, and you could do the same in your code, as so:

public class MyResource {
    @Context
    private ContextResolver mapperResolver;

    public void someResourceMethod() {
        final ObjectMapper mapper = mapperResolver.getContext(Object.class);
    }
}