Jackson and Gson are the most complete Java JSON packages regarding actual data binding support; many other packages only provide primitive Map/List (or equivalent tree model) binding. Both have complete support for generic types, as well, as enough configurability for many common use cases.

Since I am more familiar with Jackson, here are some aspects where I think Jackson has more complete support than Gson (apologies if I miss a Gson feature):

• Extensive annotation support; including full inheritance, and advanced "mix-in" annotations (associate annotations with a class for cases where you can not directly add them)
• Streaming (incremental) reading, writing, for ultra-high performance (or memory-limited) use cases; can mix with data binding (bind sub-trees) -- EDIT: latest versions of Gson also include streaming reader
• Tree model (DOM-like access); can convert between various models (tree <-> java object <-> stream)
• Can use any constructors (or static factory methods), not just default constructor
• Field and getter/setter access (earlier gson versions only used fields, this may have changed)
• Out-of-box JAX-RS support
• Interoperability: can also use JAXB annotations, has support/work-arounds for common packages (joda, ibatis, cglib), JVM languages (groovy, clojure, scala)
• Ability to force static (declared) type handling for output
• Support for deserializing polymorphic types (Jackson 1.5) -- can serialize AND deserialize things like List correctly (with additional type information)
• Integrated support for binary content (base64 to/from JSON Strings)

Figured it out how to do it correctly using Java Objects.

Creator creator = new Creator("John");
new Gson().toJson(creator);

Implementation of Creator java class.

public class Creator {

    protected HashMap<String, String> publisher = new HashMap<String, String>();

    public Creator(String name){
            publisher.put("name", name);
    }
}