GWT Map

map.java

/**
 * Map
 * 
 * @author jldupont
 */
package com.cdf.front.types.client;

import java.util.Iterator;
import java.util.Set;

import com.google.gwt.json.client.JSONObject;
import com.google.gwt.json.client.JSONString;

public class Map {

	JSONObject jso=new JSONObject();
	
	public Map() {}
	
	public void putFromJso(JSONObject jso) {
		
		Set<String> keys=jso.keySet();
		Iterator<String> it=keys.iterator();
		while(it.hasNext()) {
			String key=it.next();
			this.store(key, jso.get(key).toString());
		}
	}
	
	public void store(String key, String value) {
		jso.put(key, new JSONString(value));
	}
	
	public String retrieve(String key) {
		return jso.get(key).isString().stringValue();
	}
	
	/*
	 * @todo write native method
	 */
	public final void iterate(IMapVisitor<String> visitor) {
		Set<String> keys=jso.keySet();
		Iterator<String> it=keys.iterator();
		
		while (it.hasNext()) {
			String key=it.next();
			visitor.visit(key, this.retrieve(key));
		}
	}
	
}///

Why extend JSONObject when you can wrap it? Also, "doing" things in a constructor is generally seen as bad practice (use a factory method or a distinct putAll(JSONObject) method instead).
Oh, and if you're going to "store" directly into a JSONObject, then I'd rather use JSNI (rather than wrapping everything in JSONValue-s, which adds unnecessary overhead; have a look at how JsoSplittable –which backs AutoBean on the client-side– works)

1. Updated the gist based on your comment - Thanks!
2. I am not using JSNI because it was causing me grief with regards to the generic IMapVisitor. Anyhow this class doesn't need to be very optimized.

Thanks :)