Create Extensionpoint in plugin and access that in a different one

[lyze237]

Dear Developer,

I'm currently struggling with the following thing:

I have a plugin which creates some extension points for other plugins.
Now I want those other plugins to use those extension points and use those plugins then inside my project.

E.g.:

Plugin CommandProvider: Has a interface: public interface CommandExtension extends ExtensionPoint

Plugin TestPlugin: Has a plugin public class TestPlugin extends Plugin which has a class inside @Extension public static class TestExtension implements CommandExtension

---

Now I want to access every CommandExtension from my CommandProvider:

for (CommandExtension commandExtension : comandPluginWrapper.getPluginManager().getExtensions(CommandExtension.class)) {
                if (commandExtension.canCall(pluginId, event)) {
                    commandExtension.call(pluginId, event);
                }
            }

This however returns always 0 Command Extension Points.

The following test however says that the plugin has the proper extension point:

   public void processEvent(String pluginId, Event event) {
        PluginWrapper plugin = wrapper.getPluginManager().getPlugin("Test Service");

        for (String extension : plugin.getPluginManager().getExtensionClassNames(plugin.getPluginId())) {
            logger.debug("Found Extension " + extension);
            try {
                for (Class<?> clazz : plugin.getPluginClassLoader().loadClass(extension).getInterfaces()) {
                    logger.warn(clazz.getName());
                }
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }

        logger.warn("Found Command Extension " + plugin.getPluginManager().getExtensions(CommandExtension.class).size() + " times");
        if (event instanceof GenericMessageChatToBotEvent || event instanceof GenericMessageBotToChatEvent) {
            for (CommandExtension commandExtension : plugin.getPluginManager().getExtensions(CommandExtension.class)) {
                if (commandExtension.canCall(pluginId, event)) {
                    commandExtension.call(pluginId, event);
                }
            }
        }
    }
}

This produces the following output:

GlobalCommandPlugin - Found Command Extension 0 times
GlobalCommandPlugin - Found Extension at.lyze.plugin.testPlugin.TestPlugin$TestExtension:
GlobalCommandPlugin - at.lyze.pluginApi.extensions.services.ServiceExtension
GlobalCommandPlugin - at.lyze.plugin.globalCommandPlugin.CommandExtension

Do I do something wrong here?

[decebals]

Check to see that extensions.idx file is generated for TestPlugin. If you can, please supply the log file (with level on debug).

[lyze237]

Testplugin idx file:

# Generated by PF4J
at.lyze.plugin.testPlugin.TestPlugin$TestExtension
at.lyze.plugin.testPlugin.TestPlugin$TestExtension

Command Plugin idx file:

# Generated by PF4J
at.lyze.plugin.globalCommandPlugin.GlobalCommandPlugin$EventProcessor

Log File: Search for "WARN" to find the outputs: http://pastebin.com/Q3cH5uL3

Currently the plugin zips look like this:

• TestPlugin
  • lib
    • CommandPlugin.jar (That's the unmodified jar, so class files are direct in the root directory)
  • classes
    • normal classfiles
    • meta-inf directory with extensions.idx and manifest.mf
• CommandPlugin
  • classes
    • normal classfiles
    • meta-inf directory with extensions.idx and manifest.mf

[decebals]

# Generated by PF4J
at.lyze.plugin.testPlugin.TestPlugin$TestExtension
at.lyze.plugin.testPlugin.TestPlugin$TestExtension

I don't like that you have duplicate lines in extensions.idx

I will investigate the log file and I will come with conclusions.

[lyze237]

If you need the sources to investigate it better: https://bitbucket.org/lyze237/darkowlbot/src/15e6cb7902db197cc812d41b055934e70219e9a0/plugins?at=dev

[decebals]

If I search after Finding extensions for extension point 'at.lyze.plugin.globalCommandPlugin.CommandExtension' I retrieved (line 310):

2016-03-21 16:21:04,652 DEBUG ro.fortsoft.pf4j.AbstractExtensionFinder - Loading class 'at.lyze.plugin.testPlugin.TestPlugin$TestExtension' using class loader 'ro.fortsoft.pf4j.PluginClassLoader@621be5d1'
2016-03-21 16:21:04,652 DEBUG ro.fortsoft.pf4j.AbstractExtensionFinder - Checking extension type 'at.lyze.plugin.testPlugin.TestPlugin$TestExtension'
2016-03-21 16:21:04,652 DEBUG ro.fortsoft.pf4j.AbstractExtensionFinder - 'at.lyze.plugin.testPlugin.TestPlugin$TestExtension' is not an extension for extension point 'at.lyze.plugin.globalCommandPlugin.CommandExtension'

If you found PluginClassLoader@621be5d1 you can see that:

2016-03-21 16:20:59,792 DEBUG ro.fortsoft.pf4j.DefaultPluginManager - Loading plugin '/testPlugin-16-03-21_16_20'
2016-03-21 16:20:59,792 DEBUG ro.fortsoft.pf4j.DefaultPluginManager - Created class loader 'ro.fortsoft.pf4j.PluginClassLoader@621be5d1'

so it's OK

The problem is why 'at.lyze.plugin.testPlugin.TestPlugin$TestExtension' is not an extension for extension point 'at.lyze.plugin.globalCommandPlugin.CommandExtension'?
The above line is generated by AbstractExtensionFinder.find(Class<T> type) if type.isAssignableFrom(extensionClass) return false.
Here are two possible causes:

• something is wrong related to how you mark the extension point or extension
• CommandExtension and TestExtension is loaded by two different class loaders

[lyze237]

CommandExtension is used by both plugins so it needs to be loaded by their two classloaders? (Or am I wrong here?)

For clarification, those are the two files:

CommandPlugin.CommandExtension

public interface CommandExtension extends ExtensionPoint {
    boolean canCall(String pluginId, Event event);
    void call(String pluginId, Event event);
}

TestPlugin.TestPlugin

public class TestPlugin extends Plugin {
    @Extension
    public static class TestExtension implements ServiceExtension, CommandExtension {
        @Override
        public boolean canCall(String pluginId, Event event) {
            return true;
        }

        @Override
        public void call(String pluginId, Event event) {
            logger.warn("Command got called! " + event);
        }
    }
}

[decebals]

The idea is : if Plugin_1 declares the extension point ExtensionPoint_1 than if in Plugin_2 you want to provide an extension for ExtensionPoint_1 you must specify that Plugin_1 is a dependency for Plugin_2 (in plugin manifest file).

I don't know if I can create a defense (a warning in log) to highlight this type of problems.

Please make the modifications and tell me if the problem disappears.

[lyze237]

Ah oh god I forgot that exists.
I'm sorry, that worked!

[decebals]

Good. Please close the issue if the problem is resolved.

[lyze237]

Thanks again for the quick help!
And I#m sorry that I forgot about that X)

[decebals]

No problem