Question

I am loading a plug-in dynamically. Both the plug-in and the software
have been created by us.

I have an Interface lets call it Foo. There is also FooImpl that just
implements that method But FooImpl is in the jar loaded dynamically
public interface Foo {
void write(..someArgument..) throws Exception; }

I have also a PluginLoader class here is the method

 public
Object loadPlugin(final String jarPath, final Class
pluginInterface) {
    try
    {
        final URI uri = new File(jarPath).toURI();
        final URL url = uri.toURL();


    final URLClassLoader ucl = new URLClassLoader(new URL[] { url });
    try
    {
         final Class<?> pluginClass = Class.forName("FooImpl", true, ucl);

         // Verify if plugin implements plugin interface.
         if (pluginClass.getInterfaces()[0].getName().equals(pluginInterface.getName()))
         {
          // Instantiate plugin.
          return pluginClass.newInstance();

         } }//[...] </code></pre>

This part is actually working well i think so because after doing some
sysout on the pluginClass i notice:
the .getMethods() =
[public void FooImpl.write(..someArgumentType..) throws Exception,
public abstract void some.package.Foo.write(..someArgumentType..)
throws Exception]

the .getGenericInterfaces() = [interface some.package.Foo]

But when i try to call the method write here is what i get
java.lang.AbstractMethodError: FooImpl.write(..SomeArgumentType..;)V

I dont know why there is a “;” and a “V”

So basically i think that it try to call the interface method instead
of the implemented one. So i’m wondering What is going on!

As usual, Thank you for your time and help

Answer 1

An AbstractMethodError suggests that your code is trying to use a different version of a class at runtime compared to the class it was originally built against. You need to ensure that in your execution environment, there isn’t a rogue version of your interface implementation on the classpath.