"java.lang.VerifyError: Cannot inherit from final class" when running GWTTestCase

Question

I just wrote my very first GWTTestCase but running it always gives me a VerifyError. Here's my embryo of a great testsuite to be :

public void test() {
    Invoice invoice = new Invoice();
    invoice.setInvoiceDate(DateTimeFormat.getFormat(DomainResource.DATE_PATTERN).format(new Date()));
    InvoiceEditorDriver driver = GWT.create(InvoiceEditorDriver.class);
    InvoiceNumberEditor editor = new InvoiceNumberEditor();
    driver.initialize(editor);
    driver.edit(invoice);

    assertFalse(driver.isDirty());
    }

For completeness, I use Google AppEngine and GWT together, and I think this may relate to the security sandbox of AppEngine.

The class that is being loaded is "com.gargoylesoftware.htmlunit.SocksSocketFactory".

The full stacktrace here :

Exception in thread "htmlUnit client thread" java.lang.VerifyError: Cannot inherit from final class
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at com.gargoylesoftware.htmlunit.HttpWebConnection.createHttpClient(HttpWebConnection.java:542)
    at com.gargoylesoftware.htmlunit.HttpWebConnection.getHttpClient(HttpWebConnection.java:506)
    at com.gargoylesoftware.htmlunit.HttpWebConnection.getResponse(HttpWebConnection.java:150)
    at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseFromWebConnection(WebClient.java:1281)
    at com.gargoylesoftware.htmlunit.WebClient.loadWebResponse(WebClient.java:1198)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:307)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:376)
    at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:361)
    at com.google.gwt.junit.RunStyleHtmlUnit$HtmlUnitThread.run(RunStyleHtmlUnit.java:136)

I tried excluding GAE validation for given class but without success. I'm not sure if excluding validation is sufficient and if it's possilble to setup validation exclude rules for files in a jar.

Answer 1

Might be a classpath problem.

There was a similar problem on the mailing list, solved by removing a second instance of the PlainSocketFactory from the classpath.