java通知机制_Java事件通知机制 比眉伴天荒 2022-11-04 15:27 160阅读 0赞 3 解析pf4j 3.1 定义事件 package ro.fortsoft.pf4j; import java.util.EventObject; /\*\* \* @author Decebal Suiu \*/ public class PluginStateEvent extends EventObject \{ private PluginWrapper plugin; private PluginState oldState; public PluginStateEvent(PluginManager source, PluginWrapper plugin, PluginState oldState) \{ super(source); this.plugin = plugin; this.oldState = oldState; \} @Override public PluginManager getSource() \{ return (PluginManager) super.getSource(); \} public PluginWrapper getPlugin() \{ return plugin; \} public PluginState getPluginState() \{ return plugin.getPluginState(); \} public PluginState getOldState() \{ return oldState; \} @Override public String toString() \{ return "PluginStateEvent \[plugin=" + plugin.getPluginId() + ", newState=" + getPluginState() + ", oldState=" + oldState + '\]'; \} \} 3.2 定义监听器 package ro.fortsoft.pf4j; import java.util.EventListener; /\*\* \* PluginStateListener defines the interface for an object that listens to plugin state changes. \* \* @author Decebal Suiu \*/ public interface PluginStateListener extends EventListener \{ /\*\* \* Invoked when a plugin's state (for example DISABLED, STARTED) is changed. \*/ public void pluginStateChanged(PluginStateEvent event); \} 3.3 监听器实现 package ro.fortsoft.pf4j; import java.io.IOException; import java.io.InputStreamReader; import java.io.Reader; import java.net.URL; import java.util.\*; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /\*\* \* The default implementation for ExtensionFinder. \* All extensions declared in a plugin are indexed in a file "META-INF/extensions.idx". \* This class lookup extensions in all extensions index files "META-INF/extensions.idx". \* \* @author Decebal Suiu \*/ public class DefaultExtensionFinder implements ExtensionFinder, PluginStateListener \{ private PluginManager pluginManager ; private ExtensionFactory extensionFactory ; private volatile Map> entries ; // cache by pluginId 。。。。。 @Override public void pluginStateChanged(PluginStateEvent event) \{ // TODO optimize (do only for some transitions) // clear cache entries = null ; \} \} 3.4 触发监听器 public class DefaultPluginManager implements PluginManager \{ 。。。。 @Override public boolean enablePlugin(String pluginId) \{ if (! plugins .containsKey(pluginId)) \{ throw new IllegalArgumentException(String.format( "Unknown pluginId %s" , pluginId)); \} PluginWrapper pluginWrapper = getPlugin(pluginId); if (!isPluginValid(pluginWrapper)) \{ log .warn( "Plugin '\{\}:\{\}' can not be enabled" , pluginWrapper.getPluginId(), pluginWrapper.getDescriptor().getVersion()); return false ; \} PluginDescriptor pluginDescriptor = pluginWrapper.getDescriptor(); PluginState pluginState = pluginWrapper.getPluginState(); if (PluginState. DISABLED != pluginState) \{ log .debug( "Plugin '\{\}:\{\}' is not disabled" , pluginDescriptor.getPluginId(), pluginDescriptor.getVersion()); return true ; \} try \{ if ( disabledPlugins .remove(pluginId)) \{ FileUtils. writeLines( disabledPlugins , new File( pluginsDirectory , "disabled.txt" )); \} \} catch (IOException e) \{ log .error( "Failed to enable plugin \{\}" , pluginId, e); return false ; \} pluginWrapper.setPluginState(PluginState. CREATED ); firePluginStateEvent( new PluginStateEvent( this , pluginWrapper, pluginState)); log .info( "Enabled plugin '\{\}:\{\}'" , pluginDescriptor.getPluginId(), pluginDescriptor.getVersion()); return true ; \} /\*\* \* Add the possibility to override the ExtensionFinder. \*/ protected ExtensionFinder createExtensionFinder() \{ DefaultExtensionFinder extensionFinder = new DefaultExtensionFinder( this , extensionFactory ); addPluginStateListener(extensionFinder); return extensionFinder; \} @Override public synchronized void addPluginStateListener(PluginStateListener listener) \{ pluginStateListeners .add(listener); \} @Override public synchronized void removePluginStateListener(PluginStateListener listener) \{ pluginStateListeners .remove(listener); \} 。。。。 private synchronized void firePluginStateEvent(PluginStateEvent event) \{ for (PluginStateListener listener : pluginStateListeners ) \{ log .debug( "Fire '\{\}' to '\{\}'" , event, listener); listener.pluginStateChanged(event); \} \} \}
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