DevMode launch fails in GWT JSNI project

The problematic class AmChartJSO

implements the interface IsAmChart

- all methods are declared twice in JavaScriptObject$

. Snippet from bytecode:

public final synthetic com_amcharts_api_IsAmChart_setVersion(Ljava/lang/String;)V
  ALOAD 0
  ALOAD 1
  INVOKESTATIC com/amcharts/jso/AmChartJSO$.setVersion$ (Lcom/amcharts/jso/AmChartJSO;Ljava/lang/String;)V
  RETURN
  MAXSTACK = 2
  MAXLOCALS = 2

// access flags 0x1011
public final synthetic com_amcharts_api_IsAmChart_setVersion(Ljava/lang/String;)V
  ALOAD 0
  ALOAD 1
  INVOKESTATIC com/amcharts/jso/AmChartJSO$.setVersion$ (Lcom/amcharts/jso/AmChartJSO;Ljava/lang/String;)V
  RETURN
  MAXSTACK = 2
  MAXLOCALS = 2

      

        
        
        
      

    

You seem to run into a limitation on overlay types - only one JavaScriptObject subtype can implement any given interface :

In practical terms, this means that only one JavaScriptObject type can implement any given interface, but any number of non-JavaScriptObject types can also implement this interface.

Looking at your code, this constraint is violated: AmChartJSO

implements IsAmChart

, but AmCoordinateChartJSO

implements IsAmCoordinateChart

, which extends IsAmChart

- and hence the two JSOs implement the same interface. If I understand this limitation correctly, you cannot even subclass the JSO that implements the interface.

I did a quick test and this code doesn't work either:

public class Test extends JavaScriptObject implements TakesValue<String> {
    protected Test() {
    }

    @Override
    public final void setValue(String value) {
    }

    @Override
    public final String getValue() {
        return null;
    }
}

public class Test2 extends Test {
    protected Test2() {
    }
}

      

        
        
        
      

    

With a similarly useless exception:

java.lang.NullPointerException: null
    at com.google.gwt.dev.shell.CompilingClassLoader$MySingleJsoImplData.findOverloadUsingErasure(CompilingClassLoader.java:703)
    at com.google.gwt.dev.shell.CompilingClassLoader$MySingleJsoImplData.<init>(CompilingClassLoader.java:593)
    at com.google.gwt.dev.shell.CompilingClassLoader.<init>(CompilingClassLoader.java:980)
    at com.google.gwt.dev.shell.ShellModuleSpaceHost.onModuleReady(ShellModuleSpaceHost.java:137)
    at com.google.gwt.dev.shell.ModuleSpace.onLoad(ModuleSpace.java:340)
    at com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:200)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:526)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
    at java.lang.Thread.run(Thread.java:745)

      

        
        
        
      

    

Please see this thread on the GWT mailing list for workarounds and general discussion of this issue.

To automatically unload generated class files

For future reference, you can dump the generated class

file by setting the system property gwt.dev.classDump

( -Dgwt.dev.classDump=true

). See this wiki page for more information. By default, classes are written to a folder rewritten-classes

(in your case it will be war/rewritten-classes

). Classes are organized in batches, so find JavaScriptObject$

easily: rewritten-classes/com/google/gwt/core/client/JavaScriptObject$.class

.

Now all you have to do is disassemble it - I used the Bytecode Outline plugin for Eclipse and got the bytecode JavaScriptObject$.class

.

To find out which methods were duplicated I could just load the file with class

a classloader and let the JVM figure it out ... But I felt lazy, so I just grep

ed for public final synthetic

in bytecode and run uniq -D

to see only duplicated entries.