How do I get a reference to the Jackson Object Mapper in a jersey2 / hk2 application

Question

I have a jersey2 application configured for JSON support via Jackson, adding

<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-json-jackson</artifactId>
    <version>${jersey.version}</version>
</dependency>

in the POM file and

public MyApplication() {
    ...
    register(JacksonFeature.class)
    ...
}

in my application. Everything works, my resources get deserialized POJOs as arguments

@POST @Consumes(MediaType.APPLICATION_JSON)
public void blah(MyPojo p) {
    ...
}

Now one of thoese resources needs a reference to Jackson's ObjectMapper to do some deserialization on its own. I've tried doing something like

@Inject
public MyResource(@Context ObjectMapper mapper) {
    ...
}

or

@GET
public String foo(@Context ObjectMapper mapper) {
    ...
}

but in both cases the reference to mapper is null. How can I inject a reference to the ObjectMapper in my resources?

Answer 1

Aside from the JacksonFeature you need to register a ContextResolver for ObjectMapper.

Simple example from the Documentation at 9.1.4.2. Configure and register

@Provider
public class MyObjectMapperProvider implements ContextResolver<ObjectMapper> {

    final ObjectMapper defaultObjectMapper;

    public MyObjectMapperProvider() {
        defaultObjectMapper = createDefaultMapper();
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return defaultObjectMapper;
    }

    private static ObjectMapper createDefaultMapper() {
        final ObjectMapper result = new ObjectMapper();
        result.configure(Feature.INDENT_OUTPUT, true);

        return result;
    }

    // ...
}

Complete code example available on Github

You will also need to register it

        .register(MyObjectMapperProvider.class)