HotswapAgent and Wicket

hotswap-agent.properties

autoHotswap=false
extraClasspath=\
  ./src/main/resources;\
  ./src/main/java;\
  ../other-module-1/target/classes;\
  ../other-module-2/target/classes;\
disabledPlugins=Hibernate,Spring,Tomcat,ResteasyRegistry
pluginPackages={PACKAGE_OF_WICKET_PLUGIN_JAVA}
LOGGER=info

WicketPlugin.java

import org.hotswap.agent.annotation.Init;
import org.hotswap.agent.annotation.OnClassLoadEvent;
import org.hotswap.agent.annotation.OnResourceFileEvent;
import org.hotswap.agent.annotation.Plugin;
import org.hotswap.agent.command.Scheduler;
import org.hotswap.agent.javassist.CannotCompileException;
import org.hotswap.agent.javassist.CtClass;
import org.hotswap.agent.javassist.NotFoundException;
import org.hotswap.agent.logging.AgentLogger;
import org.hotswap.agent.util.PluginManagerInvoker;

import java.lang.reflect.Method;

/**
 * Wicket support for hotswap
 */
@Plugin(name = "Wicket Plugin", testedVersions = "8.0.0")
public class WicketPlugin {

	private static final AgentLogger LOGGER = AgentLogger.getLogger(WicketPlugin.class);

	@Init
	Scheduler scheduler;
	@Init
	ClassLoader appClassLoader;

	private Object wicketApplication;

	@OnClassLoadEvent(classNameRegexp = "org.apache.wicket.protocol.http.WebApplication")
	public static void init(CtClass ctClass) throws NotFoundException, CannotCompileException {
		String src = PluginManagerInvoker
				.buildInitializePlugin(WicketPlugin.class);
		src += PluginManagerInvoker.buildCallPluginMethod(WicketPlugin.class,
				"registerApplication", "this", "java.lang.Object");
		ctClass.getDeclaredConstructor(new CtClass[0]).insertAfter(src);

		LOGGER.info("Initialized Wicket plugin");
	}

	public void registerApplication(Object wicketApplication) {
		this.wicketApplication = wicketApplication;

		LOGGER.info("Plugin {} initialized for application {}", getClass(),
				wicketApplication);
	}

	@OnResourceFileEvent(path = "/", filter = ".*.properties")
	public void clearLocalizerCaches() {
		scheduler.scheduleCommand(this::clearCache);
	}

	private void clearCache() {
		LOGGER.debug("Refreshing Wicket resource bundles.");
		try {
			final Object localizer = getLocalizer();
			final Method clearCacheMethod = resolveClass("org.apache.wicket.Localizer")
					.getDeclaredMethod("clearCache");
			clearCacheMethod.invoke(localizer);
		} catch (Exception e) {
			LOGGER.error("Error clear Wicket resource bundles cache", e);
		}
	}

	private Object getLocalizer() {
		try {
			final Method getResourceSettingsMethod = resolveClass("org.apache.wicket.Application")
					.getDeclaredMethod("getResourceSettings");
			final Method getLocalizerMethod = resolveClass("org.apache.wicket.settings.ResourceSettings")
					.getDeclaredMethod("getLocalizer");
			final Object resourceSettings = getResourceSettingsMethod.invoke(wicketApplication);
			return getLocalizerMethod.invoke(resourceSettings);
		} catch (Exception e) {
			LOGGER.error("Error getting Wicket localizer", e);
			return null;
		}
	}

	private Class<?> resolveClass(String name) throws ClassNotFoundException {
		return Class.forName(name, true, appClassLoader);
	}

}