How do I expose data in a JSON format through a web service using Java?

Question

Is there an easy way to return data to web service clients in JSON using java? I\'m fine with servlets, spring, etc.

Answer 1

I have found google-gson compelling. It converts to JSON and back. http://code.google.com/p/google-gson/ It's very flexible and can handle complexities with objects in a straightforward manner. I love its support for generics.

/*
* we're looking for results in the form
* {"id":123,"name":thename},{"id":456,"name":theOtherName},...
*
* TypeToken is Gson--allows us to tell Gson the data we're dealing with
* for easier serialization.
*/
Type mapType = new TypeToken<List<Map<String, String>>>(){}.getType();

List<Map<String, String>> resultList = new LinkedList<Map<String, String>>();

for (Map.Entry<String, String> pair : sortedMap.entrySet()) {
    Map<String, String> idNameMap = new HashMap<String, String>();
    idNameMap.put("id", pair.getKey());
    idNameMap.put("name", pair.getValue());
    resultList.add(idNameMap);
}

return (new Gson()).toJson(resultList, mapType);

Answer 2

Yup! Check out json-lib

Here is a simplified code snippet from my own code that send a set of my domain objects:

private String getJsonDocumenent(Object myObj) (
    String result = "oops";
    try {
        JSONArray jsonArray = JSONArray.fromObject(myObj);

        result = jsonArray.toString(2);  //indent = 2

    } catch (net.sf.json.JSONException je) {

        throw je;
    }
    return result;
}

Answer 3

http://www.json.org/java/index.html has what you need.