java通知机制_Java事件通知机制

比眉伴天荒 2022-11-04 15:27 226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) \{

plugins

.containsKey(pluginId)) \{

throw

new

IllegalArgumentException(String.format(

"Unknown pluginId %s"

, pluginId));

PluginWrapper pluginWrapper = getPlugin(pluginId);

(!isPluginValid(pluginWrapper)) \{

log

.warn(

"Plugin '\{\}:\{\}' can not be enabled"

, pluginWrapper.getPluginId(),

pluginWrapper.getDescriptor().getVersion());

return

false

;

PluginDescriptor pluginDescriptor = pluginWrapper.getDescriptor();

PluginState pluginState = pluginWrapper.getPluginState();

(PluginState.

DISABLED

!= pluginState) \{

log

.debug(

"Plugin '\{\}:\{\}' is not disabled"

, pluginDescriptor.getPluginId(), pluginDescriptor.getVersion());

return

true

;

try

(

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);

java通知机制_Java事件通知机制

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