jackson deserializer - get model field annotations list

Question

I'm working on a java spring mvc project. I have created CustomObjectMapper class that extends ObjectMapper form jackson. Also I set CustomObjectMapper in the spring configuration, so every time jackson wants to serialize or deserialize , my CustomObjectMapper works and everything is right. But I have one problem:

I have created a custom annotation @AllowHtml and I have put it on top of some String fields in my model. Also I have created a JsonDeserializerString class in this way:

public class JsonDeserializerString extends JsonDeserializer<String>{

    @Override
    public String deserialize(JsonParser jp, DeserializationContext dc) throws IOException, JsonProcessingException {

        return jp.getText();
    }

}

And I set this deserializer in my CustomObjectMapper in this way:

@Component
public class CustomObjectMapper extends ObjectMapper {
     public CustomObjectMapper(){
         SimpleModule module = new SimpleModule();
         module.addDeserializer(String.class, new JsonDeserializerString());
         this.registerModule(module);
     }
}

This works as expected and when a user submit a form, every string fields deserialize with JsonDeserializerString . But I want to get field annotations in the deserializer. . In fact, I want to, If a string field has a certain annotation in the model, do some logics. How can I do this?

Answer 1

Your deserializer could implement ContextualDeserializer and extract the property annotations. You could store it in a private property and reuse it while deserializing the String.

Example:

public class EmbeddedDeserializer 
    extends JsonDeserializer<Object> 
    implements ContextualDeserializer {

    private Annotation[] annotations;

    @Override
    public JsonDeserializer<?> createContextual(final DeserializationContext ctxt, 
        final BeanProperty property) throws JsonMappingException {

        annotations = property.getType().getRawClass().getAnnotations();

        return this;
    }

    @Override
    public Object deserialize(final JsonParser jsonParser, 
        final DeserializationContext context) 
            throws IOException, JsonProcessingException {

            if (annotations contains Xxxx) { ... }
        }
}

I hope it helps.