How to pass parameter to JsonSerializer?

问题

I have a simple data service :

@GET
public Data getData(@QueryParam("id") Long id) {
  Data data = dataService.getData(id);
  return data;
}

And a matching DataSerializer that implements JsonSerializer<Data> : The DataSerializer is registered to Jackson via :

simpleModule.addSerializer(Data.class , dataSerializer);
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(simpleModule);

It works well. But today , I want to add another Locale parameter , and hope the DataSerializer to output correspondent content :

@GET
public Data getData(@QueryParam("id") Long id , @QueryParam("locale") Locale locale)

The 'Data' itself contains various locale variations , and I hope to get the assigned locale output.

But when I get the locale from the parameter , I don't know how to pass the locale value to the DataSerializer …

Is there anyway to achieve this ?

Except this solution :

Data data = dataService.getData(id.get() , locale);

which is not what I want.

It seems ThreadLocal is the only way to achieve this , but I feel that is ugly. Any other feasible solutions ?

Thanks.

Environments : dropwizard-0.7.0-rc2 , jackson-core:jar:2.3.1

===================== updated ==========

reply to @andrei-i :

Because my data itself already contains various locale versions. for example :

Data helloData = dataService.get("hello");
helloData.getName(Locale.English) == "Hello";
helloData.getName(Locale.France) == "Bonjour";
helloData.getName(Locale.Germany) == "Hallo";

I want to directly pass the locale from URL to JsonSerializer , to get one version of the data presentation.

And there 'may' be other version (not just locale) , so , inheriting Data mixing Locale is not considered.

回答1:

I know that this is not a new question but here is what I came up with facing the similar problem:

created custom annotation:

@Target({ ElementType.FIELD, ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
public @interface JsonLocalizable {

  public String localizationKey();
}

Jackson serializer:

 public class LocalizingSerializer extends StdSerializer<String> implements ContextualSerializer {

      private String localizationKey;

      public LocalizingSerializer() {
        super(String.class);
      }

      public LocalizingSerializer(String key) {
        super(String.class);

        this.localizationKey = key;
      }

      @Override
      public void serialize(String value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {

        String localizedValue = //.... get the value using localizationKey

        jgen.writeString(localizedValue);
      }

      @Override
      public JsonSerializer<?> createContextual(SerializerProvider prov, BeanProperty property) throws JsonMappingException {

        String key = null;
        JsonLocalizable ann = null;

        if (property != null) {
          ann = property.getAnnotation(JsonLocalizable.class);
        }

        if (ann != null) {
          key = ann.localizationKey();
        }

        //if key== null??

        return new LocalizingSerializer(key);
      }
    }

Annotate the field you want to localize:

public class TestClass {

    @JsonSerialize(using = LocalizingSerializer.class)
    @JsonLocalizable(localizationKey = "my.key")
    private String field;

    public String getField() {
      return this.field;
    }

    public void setField(String field) {
      this.field = field;
    }
}

回答2:

Solution 1. In your JAX-RS implementation register your own implementation of MessageBodyWriter for JSON requests. Probably your implementation will extend Jackson. Also it might be possible that you will have to unregister Jackson. In a MessageBodyWriter you can inject a UriInfo instance using the @Context annotation, and with it you can get any request parameter.

Solution 2. Change the architecture of your Data, so that it is locale-aware. For example, create a setter setLocale() which will change the returned data, if the locale was set.

来源：https://stackoverflow.com/questions/22634860/how-to-pass-parameter-to-jsonserializer

标签

java

jackson

jax-rs

dropwizard

jsonserializer