使用Jackson定制JSON映射

Question

I have a POJO

class Product {
    String name;
    Size size;
} 

So, I want to map a deserialize a JSON to my POJO. If I have both the attributes in my JSON, it is not a problem.

But in my case, sometimes size will not be a part of the JSON. There might be a third attribute 'type' based on which I will set my size. I do not want to include 'type' in my POJO. Are there any Jackson annotations which can do this?

Answer 1

write your custom Deserializers:

SimpleModule module =
  new SimpleModule("ProductDeserializerModule",
      new Version(1, 0, 0, null));
module.addDeserializer(Product.class, new ProductJsonDeserializer());

mapper = new ObjectMapper();
mapper.registerModule(module);

//...

class ProductJsonDeserializer extends JsonDeserializer<Product>
{
  @Override
  public Product deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException
  {
    // handle here if exist a third attribute 'type' and create the product 
  }
}

More info here: http://wiki.fasterxml.com/JacksonHowToCustomDeserializers

Answer 2

Found a pretty simple solution for this!

When a JSON attribute is attempted to be mapped to my POJO's attribute, it just checks whether a setter exists for it.

For example, if there is an attribute type in JSON, it will try to hit a method named setType(obj) in my POJO, regardless of whether there exists an attribute named type .

This worked for me! I simply set my other attributes inside this setter.