JSNI Hello World无法正常工作

Question

I have done a simple Hello World GWT example using JSNI. It does nothing but display a message.

This is the code in an EntryPoint class:

public void onModuleLoad() {
  // TODO Auto-generated method stub
  alert("Hello World!");
 }
 native void alert(String msg) /*-{
  $wnd.alert(msg);
 }-*/;
}

I see this Exception:

java.lang.reflect.InvocationTargetException
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

Any idea why?

Answer 1

I created the sample GWT project and copied your code into the entry point and it worked fine. I think you have a deeper set up problem. I would look over your *.gwt.xml file and make sure it isn't malformed and check your GWT library references etc. Also open up the Run Configration and make sure it is a Web Application.

    /**
 * Entry point classes define <code>onModuleLoad()</code>.
 */
public class So implements EntryPoint {


    native void alert(String msg) /*-{ 
      $wnd.alert(msg); 
     }-*/; 

    /**
     * This is the entry point method.
     */
    public void onModuleLoad() {

        alert("Hello World!"); 
    }
}

Answer 2

你可能不运行在DevMode的这个代码，但在一个普通的JVM，其中GWT不能做它的魔力