The JConsolePlugin.java Java example source code
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package com.sun.tools.jconsole;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JPanel;
import javax.swing.SwingWorker;
/**
* A JConsole plugin class. JConsole uses the
* <a href="{@docRoot}/../../../../api/java/util/ServiceLoader.html">
* service provider</a> mechanism to search the JConsole plugins.
* Users can provide their JConsole plugins in a jar file
* containing a file named
*
* <blockquote>
* META-INF/services/com.sun.tools.jconsole.JConsolePlugin</pre>
*
* <p> This file contains one line for each plugin, for example,
*
* <blockquote>
* com.sun.example.JTop</pre>
* <p> which is the fully qualified class name of the class implementing
* {@code JConsolePlugin}.
*
* <p> To load the JConsole plugins in JConsole, run:
*
* <blockquote>
* jconsole -pluginpath <plugin-path> </pre>
*
* <p> where <plugin-path> specifies the paths of JConsole
* plugins to look up which can be a directory or a jar file. Multiple
* paths are separated by the path separator character of the platform.
*
* <p> When a new JConsole window is created for a connection,
* an instance of each {@code JConsolePlugin} will be created.
* The {@code JConsoleContext} object is not available at its
* construction time.
* JConsole will set the {@link JConsoleContext} object for
* a plugin after the plugin object is created. It will then
* call its {@link #getTabs getTabs} method and add the returned
* tabs to the JConsole window.
*
* @see <a href="{@docRoot}/../../../../api/java/util/ServiceLoader.html">
* java.util.ServiceLoader</a>
*
* @since 1.6
*/
@jdk.Exported
public abstract class JConsolePlugin {
private volatile JConsoleContext context = null;
private List<PropertyChangeListener> listeners = null;
/**
* Constructor.
*/
protected JConsolePlugin() {
}
/**
* Sets the {@link JConsoleContext JConsoleContext} object representing
* the connection to an application. This method will be called
* only once after the plugin is created and before the {@link #getTabs}
* is called. The given {@code context} can be in any
* {@link JConsoleContext#getConnectionState connection state} when
* this method is called.
*
* @param context a {@code JConsoleContext} object
*/
public final synchronized void setContext(JConsoleContext context) {
this.context = context;
if (listeners != null) {
for (PropertyChangeListener l : listeners) {
context.addPropertyChangeListener(l);
}
// throw away the listener list
listeners = null;
}
}
/**
* Returns the {@link JConsoleContext JConsoleContext} object representing
* the connection to an application. This method may return <tt>null
* if it is called before the {@link #setContext context} is initialized.
*
* @return the {@link JConsoleContext JConsoleContext} object representing
* the connection to an application.
*/
public final JConsoleContext getContext() {
return context;
}
/**
* Returns the tabs to be added in JConsole window.
* <p>
* The returned map contains one entry for each tab
* to be added in the tabbed pane in a JConsole window with
* the tab name as the key
* and the {@link JPanel} object as the value.
* This method returns an empty map if no tab is added by this plugin.
* This method will be called from the <i>Event Dispatch Thread
* once at the new connection time.
*
* @return a map of a tab name and a {@link JPanel} object
* representing the tabs to be added in the JConsole window;
* or an empty map.
*/
public abstract java.util.Map<String, JPanel> getTabs();
/**
* Returns a {@link SwingWorker} to perform
* the GUI update for this plugin at the same interval
* as JConsole updates the GUI.
* <p>
* JConsole schedules the GUI update at an interval specified
* for a connection. This method will be called at every
* update to obtain a {@code SwingWorker} for each plugin.
* <p>
* JConsole will invoke the {@link SwingWorker#execute execute()}
* method to schedule the returned {@code SwingWorker} for execution
* if:
* <ul>
* <li> the SwingWorker object has not been executed
* (i.e. the {@link SwingWorker#getState} method
* returns {@link javax.swing.SwingWorker.StateValue#PENDING PENDING}
* state); and</li>
* <li> the SwingWorker object returned in the previous
* update has completed the task if it was not <tt>null
* (i.e. the {@link SwingWorker#isDone SwingWorker.isDone} method
* returns <tt>true).
* </ul>
* <br>
* Otherwise, <tt>SwingWorker object will not be scheduled to work.
*
* <p>
* A plugin can schedule its own GUI update and this method
* will return <tt>null.
*
* @return a <tt>SwingWorker to perform the GUI update; or
* <tt>null.
*/
public abstract SwingWorker<?,?> newSwingWorker();
/**
* Dispose this plugin. This method is called by JConsole to inform
* that this plugin will be discarded and that it should free
* any resources that it has allocated.
* The {@link #getContext JConsoleContext} can be in any
* {@link JConsoleContext#getConnectionState connection state} when
* this method is called.
*/
public void dispose() {
// Default nop implementation
}
/**
* Adds a {@link PropertyChangeListener PropertyChangeListener}
* to the {@link #getContext JConsoleContext} object for this plugin.
* This method is a convenient method for this plugin to register
* a listener when the {@code JConsoleContext} object may or
* may not be available.
*
* <p>For example, a plugin constructor can
* call this method to register a listener to listen to the
* {@link JConsoleContext.ConnectionState connectionState}
* property changes and the listener will be added to the
* {@link JConsoleContext#addPropertyChangeListener JConsoleContext}
* object when it is available.
*
* @param listener The {@code PropertyChangeListener} to be added
*
* @throws NullPointerException if {@code listener} is {@code null}.
*/
public final void addContextPropertyChangeListener(PropertyChangeListener listener) {
if (listener == null) {
throw new NullPointerException("listener is null");
}
if (context == null) {
// defer registration of the listener until setContext() is called
synchronized (this) {
// check again if context is not set
if (context == null) {
// maintain a listener list to be added later
if (listeners == null) {
listeners = new ArrayList<PropertyChangeListener>();
}
listeners.add(listener);
return;
}
}
}
context.addPropertyChangeListener(listener);
}
/**
* Removes a {@link PropertyChangeListener PropertyChangeListener}
* from the listener list of the {@link #getContext JConsoleContext}
* object for this plugin.
* If {@code listener} was never added, no exception is
* thrown and no action is taken.
*
* @param listener the {@code PropertyChangeListener} to be removed
*
* @throws NullPointerException if {@code listener} is {@code null}.
*/
public final void removeContextPropertyChangeListener(PropertyChangeListener listener) {
if (listener == null) {
throw new NullPointerException("listener is null");
}
if (context == null) {
// defer registration of the listener until setContext() is called
synchronized (this) {
// check again if context is not set
if (context == null) {
if (listeners != null) {
listeners.remove(listener);
}
return;
}
}
}
context.removePropertyChangeListener(listener);
}
}
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