A simple example using JsInterop to export for third party api use.

JsInteropExportExample.java

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.HTML;
import com.google.gwt.user.client.ui.IsWidget;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.Widget;
import com.sencha.gwt.jsinterop.examples.processor.Example;

import jsinterop.annotations.JsType;

/**
 * Don't forget to add -generateJsInteropExports to the compiler arguments for use in production.
 */
@Example(name = "JsInterop Export Example", category = "GWT", icon = "java")
public class JsInteropExportExample implements EntryPoint, IsWidget {

  @JsType(namespace = "myapi")
  public static class User {
    public String firstName;
    public String lastName;

    public final String getFullName() {
      return firstName + " " + lastName;
    }
  }

  private HTML widget;

  @Override
  public void onModuleLoad() {
    RootPanel.get().add(this);
  }

  @Override
  public Widget asWidget() {
    if (widget == null) {

      User person = new User();
      person.firstName = "Brandon";
      person.lastName = "Donnelson";

      widget = new HTML("FullName=" + person.firstName);
    }

    return widget;
  }

}