guice

jackson-module-guice

Documentation

This extension allows Jackson to delegate ObjectMapper creation and value injection to Guice when handling data bindings. Using the ObjectMapperModule you can register Jackson data binding modules like so:

  Injector injector = Guice.createInjector(
    new ObjectMapperModule().registerModule(new IntegerAsBase16Module())
  );


  public class IntegerAsBase16Module extends SimpleModule
  {
    public IntegerAsBase16Module() {
      super("IntegerAsBase16");

      addSerializer( Integer.class,
          new JsonSerializer<Integer>() {
            @Override
            public void serialize( Integer integer, JsonGenerator jsonGenerator, SerializerProvider serializerProvider )
               throws IOException, JsonProcessingException
            {
              jsonGenerator.writeString(new BigInteger(String.valueOf(integer)).toString(16).toUpperCase());
            }
          }
      );
    }
  }

Subsequently, the ObjectMapper, created from the Guice injector above, will apply the proper data bindings to serialize Integers as base 16 strings:

  mapper.writeValueAsString(new Integer(10)) ==> "A"

Additional Guice Modules can be used when creating the Injector to automatically inject values into value objects being de-serialized. The @JacksonInject annotation can be used to trigger Guice driven injection.

Here's an example of a value object where Guice injects three of the members on behalf of Jackson. The first uses the @JacksonInject annotation, the second uses @JacksonInject with a specific Named binding, and the third uses @JacksonInject combined with another annotation (@Ann).

  public class SomeBean {
    @JacksonInject
    private int one;

    @JacksonInject
    @Named("two")
    private int two;

    @JacksonInject
    @Ann
    private int three;

    @JsonProperty
    private int four;

    public boolean verify() {
      Assert.assertEquals(1, one);
      Assert.assertEquals(2, two);
      Assert.assertEquals(3, three);
      Assert.assertEquals(4, four);
      return true;
    }
  }

The last, the fourth field, annotated with @JsonProperty uses standard ObjectMapper behavior unlike the other three which are injected by Guice. The following code snippet demonstrates Guice injection leading to a true return on the verify() method:

  final Injector injector = Guice.createInjector(
      new ObjectMapperModule(),
      new Module()
      {
        @Override
        public void configure(Binder binder)
        {
          binder.bind(Integer.class).toInstance(1);
          binder.bind(Integer.class).annotatedWith(Names.named("two")).toInstance(2);
          binder.bind(Integer.class).annotatedWith(Ann.class).toInstance(3);
        }
      }
  );

  final ObjectMapper mapper = injector.getInstance(ObjectMapper.class);
  mapper.readValue("{\"four\": 4}", SomeBean.class).verify();