Question

I am looking for a simple Json (de)serializer for Java that might work with GWT. I have googled a bit and found some solutions that either require annotate every member or define useless interfaces. Quite a boring. Why don’t we have something really simple like

class MyBean {
    ...
}

new GoodSerializer().makeString(new MyBean());
new GoodSerializer().makeObject("{ ... }", MyBean.class)

Answer 1

Take a look at GWT’s Overlay Types. I think this is by far the easiest way to work with JSON in GWT. Here’s a modified code example from the linked article:

public class Customer extends JavaScriptObject {
    public final native String getFirstName() /*-{ 
        return this.first_name;
    }-*/;
    public final native void setFirstName(String value) /*-{
        this.first_name = value;
    }-*/;
    public final native String getLastName() /*-{
        return this.last_name;
    }-*/;
    public final native void setLastName(String value) /*-{
        this.last_name = value;
    }-*/;
}

Once you have the overlay type defined, it’s easy to create a JavaScript object from JSON and access its properties in Java:

public static final native Customer buildCustomer(String json) /*-{
    return eval('(' + json + ')');
}-*/;

If you want the JSON representation of the object again, you can wrap the overlay type in a JSONObject:

Customer customer = buildCustomer("{'Bart', 'Simpson'}");
customer.setFirstName("Lisa");
// Displays {"first_name":"Lisa","last_name":"Simpson"}
Window.alert(new JSONObject(customer).toString());