Support shared event mechanism

Signed-off-by: John Niang <[email protected]>

application/src/main/java/run/halo/app/plugin/DefaultPluginApplicationContextFactory.java

@@ -14,6 +14,7 @@
 import org.springframework.boot.env.PropertySourceLoader;
 import org.springframework.boot.env.YamlPropertySourceLoader;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.event.ContextClosedEvent;
 import org.springframework.context.event.ContextRefreshedEvent;
@@ -28,7 +29,6 @@
 import org.springframework.web.reactive.function.server.RouterFunction;
 import org.springframework.web.reactive.function.server.ServerResponse;
 import reactor.core.Exceptions;
-import run.halo.app.PluginApplicationContextFactory;
 import run.halo.app.extension.ReactiveExtensionClient;
 import run.halo.app.infra.properties.HaloProperties;
 import run.halo.app.plugin.event.HaloPluginBeforeStopEvent;
@@ -133,6 +133,15 @@ public ApplicationContext create(String pluginId) {
                     pluginRouterFunctionManager
                 );
             });
+
+        rootContext.getBeanProvider(SharedEventListenerRegistry.class)
+            .ifUnique(listenerRegistry -> {
+                var shareEventListenerAdapter = new ShareEventListenerAdapter(listenerRegistry);
+                beanFactory.registerSingleton(
+                    "shareEventListenerAdapter",
+                    shareEventListenerAdapter
+                );
+            });
         sw.stop();
 
         sw.start("LoadComponents");
@@ -162,6 +171,31 @@ public ApplicationContext create(String pluginId) {
         return context;
     }
 
+    private static class ShareEventListenerAdapter {
+
+        private final SharedEventListenerRegistry listenerRegistry;
+
+        private ApplicationListener<ApplicationEvent> listener;
+
+        private ShareEventListenerAdapter(SharedEventListenerRegistry listenerRegistry) {
+            this.listenerRegistry = listenerRegistry;
+        }
+
+        @EventListener
+        public void onApplicationEvent(ContextRefreshedEvent event) {
+            this.listener = sharedEvent -> event.getApplicationContext().publishEvent(sharedEvent);
+            listenerRegistry.register(this.listener);
+        }
+
+        @EventListener(ContextClosedEvent.class)
+        public void onApplicationEvent() {
+            if (this.listener != null) {
+                this.listenerRegistry.unregister(this.listener);
+            }
+        }
+
+    }
+
     private static class FinderManager {
 
         private final String pluginId;

application/src/main/java/run/halo/app/plugin/DefaultSharedEventListenerRegistry.java

@@ -0,0 +1,34 @@
+package run.halo.app.plugin;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import org.springframework.context.ApplicationEvent;
+import org.springframework.context.ApplicationListener;
+import org.springframework.stereotype.Component;
+
+@Component
+public class DefaultSharedEventListenerRegistry implements
+    ApplicationListener<ApplicationEvent>, SharedEventListenerRegistry {
+
+    private final List<ApplicationListener<ApplicationEvent>> listeners;
+
+    public DefaultSharedEventListenerRegistry() {
+        listeners = new CopyOnWriteArrayList<>();
+    }
+
+    @Override
+    public void onApplicationEvent(ApplicationEvent event) {
+        if (!event.getClass().isAnnotationPresent(SharedEvent.class)) {
+            return;
+        }
+        listeners.forEach(listener -> listener.onApplicationEvent(event));
+    }
+
+    public void register(ApplicationListener<ApplicationEvent> listener) {
+        this.listeners.add(listener);
+    }
+
+    public void unregister(ApplicationListener<ApplicationEvent> listener) {
+        this.listeners.remove(listener);
+    }
+}

application/src/main/java/run/halo/app/PluginApplicationContextFactory.java → application/src/main/java/run/halo/app/plugin/PluginApplicationContextFactory.java

@@ -1,4 +1,4 @@
-package run.halo.app;
+package run.halo.app.plugin;
 
 import org.springframework.context.ApplicationContext;
 

application/src/main/java/run/halo/app/plugin/SharedEventListenerRegistry.java

@@ -0,0 +1,12 @@
+package run.halo.app.plugin;
+
+import org.springframework.context.ApplicationEvent;
+import org.springframework.context.ApplicationListener;
+
+public interface SharedEventListenerRegistry {
+
+    void register(ApplicationListener<ApplicationEvent> listener);
+
+    void unregister(ApplicationListener<ApplicationEvent> listener);
+
+}

application/src/main/java/run/halo/app/plugin/SpringPlugin.java

@@ -3,7 +3,6 @@
 import org.pf4j.Plugin;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ConfigurableApplicationContext;
-import run.halo.app.PluginApplicationContextFactory;
 import run.halo.app.plugin.event.SpringPluginStartedEvent;
 import run.halo.app.plugin.event.SpringPluginStartingEvent;
 import run.halo.app.plugin.event.SpringPluginStoppingEvent;

application/src/main/java/run/halo/app/plugin/SpringPluginFactory.java

@@ -4,7 +4,6 @@
 import org.pf4j.Plugin;
 import org.pf4j.PluginFactory;
 import org.pf4j.PluginWrapper;
-import run.halo.app.PluginApplicationContextFactory;
 
 /**
  * The default implementation for PluginFactory.