GWT - JavaScript Overlay Types and JSON

Question

I was the Google Codeing Basics (http://code.google.com/intl/de-DE/webtoolkit/doc/latest/DevGuideCodingBasicsOverlay.html#example-collections) and thought: hey this could be way faster and easier to use than pharsing my JSON object by hand.

So I played with the example and noticed that it worked fine when the JsArray was defined in the HTML file but I couldn't find a solution to pass a String or Url into the function and it returns me an Overlay Type.

So what I want to do is:

I have this function

    private native Customer getFirstCustomer(/*TYPE (preferd String)*/ name) /*-{
    return (CASTVALUE TO ???) name; 
}-*/;

To which I pass

{"FirstName": "Jimmy"}

as String, and It returns me a Java Object like this:

    import com.google.gwt.core.client.JavaScriptObject;
    class Customer extends JavaScriptObject {
      protected Customer() { }
      public final native String getFirstName() /*-{ return this.FirstName; }-*/;
    }

Is this possible?

Best regards, Stefan

Answer 1

Please, do not, by any mean, eval() things blindly! (security 101)

Use GWT's JsonUtils instead: it'll use native JSON support in browsers that support it (faster and safer than eval()) and will validate the JSON before eval()ing it in others (that is, IE6, IE7 and old Safaris –pre 4.0.3–, all other browser versions without native JSON are dead by now):

Customer customer = JsonUtils.safeEval(jsonString);

Answer 2

If you have a JSON string, in order to create the javscript object, you must eval it:

private native Customer getFirstCustomer(String jsonString) /*-{
    return eval(jsonString);
}-*/;

If your native method returns your Customer class (it must extends JavaScriptObject) it will be casted automagically (the Java compiler will accept it, in JS it will not need casting).

See this reference too.

Important security update:

Thanks to Thomas Broyer

Don't use eval directly. Use JsonUtils.safeEval(String) (API). It will avoid executing unsafe javascript code that could come in the string.

private native Customer getFirstCustomer(String jsonString) /*-{
    return JsonUtils.safeEval(jsonString);
}-*/;