# Class JConsolePlugin

java.lang.Object
com.sun.tools.jconsole.JConsolePlugin

public abstract class JConsolePlugin extends Object
A JConsole plugin class. JConsole uses the `service provider` mechanism to search the JConsole plugins. Users can provide their JConsole plugins in a jar file containing a file named

>     META-INF/services/com.sun.tools.jconsole.JConsolePlugin

This file contains one line for each plugin, for example,

>     com.sun.example.JTop

which is the fully qualified class name of the class implementing `JConsolePlugin`.

To load the JConsole plugins in JConsole, run:

>     jconsole -pluginpath <plugin-path>

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.

When a new JConsole window is created for a connection, an instance of each `JConsolePlugin` will be created. The `JConsoleContext` object is not available at its construction time. JConsole will set the `JConsoleContext` object for a plugin after the plugin object is created. It will then call its `getTabs` method and add the returned tabs to the JConsole window.

Since:
  1.6
See Also:
  - `ServiceLoader`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `JConsolePlugin()`
  Constructor.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `final void`
  `addContextPropertyChangeListener(PropertyChangeListener listener)`
  Adds a `PropertyChangeListener` to the `JConsoleContext` object for this plugin.
  `void`
  `dispose()`
  Dispose this plugin.
  `final JConsoleContext`
  `getContext()`
  Returns the `JConsoleContext` object representing the connection to an application.
  `abstract Map<String,JPanel>`
  `getTabs()`
  Returns the tabs to be added in JConsole window.
  `abstract SwingWorker<?,?>`
  `newSwingWorker()`
  Returns a `SwingWorker` to perform the GUI update for this plugin at the same interval as JConsole updates the GUI.
  `final void`
  `removeContextPropertyChangeListener(PropertyChangeListener listener)`
  Removes a `PropertyChangeListener` from the listener list of the `JConsoleContext` object for this plugin.
  `final void`
  `setContext(JConsoleContext context)`
  Sets the `JConsoleContext` object representing the connection to an application.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### JConsolePlugin

    protected JConsolePlugin()
    Constructor.

- ## Method Details

  - ### setContext

    public final void setContext(JConsoleContext context)
    Sets the `JConsoleContext` object representing the connection to an application. This method will be called only once after the plugin is created and before the `getTabs()` is called. The given `context` can be in any `connection state` when this method is called.
    Parameters:
      `context` - a `JConsoleContext` object

  - ### getContext

    public final JConsoleContext getContext()
    Returns the `JConsoleContext` object representing the connection to an application. This method may return `null` if it is called before the `context` is initialized.
    Returns:
      the `JConsoleContext` object representing the connection to an application.

  - ### getTabs

    public abstract Map<String,JPanel> getTabs()
    Returns the tabs to be added in JConsole window.

    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 `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 Event Dispatch Thread once at the new connection time.

    Returns:
      a map of a tab name and a `JPanel` object representing the tabs to be added in the JConsole window; or an empty map.

  - ### newSwingWorker

    public abstract SwingWorker<?,?> newSwingWorker()
    Returns a `SwingWorker` to perform the GUI update for this plugin at the same interval as JConsole updates the GUI.

    JConsole schedules the GUI update at an interval specified for a connection. This method will be called at every update to obtain a `SwingWorker` for each plugin.

    JConsole will invoke the `execute()` method to schedule the returned `SwingWorker` for execution if:

    - the `SwingWorker` object has not been executed (i.e. the `SwingWorker.getState()` method returns `PENDING` state); and
    - the `SwingWorker` object returned in the previous update has completed the task if it was not `null` (i.e. the `SwingWorker.isDone` method returns `true`).
    Otherwise, `SwingWorker` object will not be scheduled to work.

    A plugin can schedule its own GUI update and this method will return `null`.

    Returns:
      a `SwingWorker` to perform the GUI update; or `null`.

  - ### dispose

    public void dispose()
    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 `JConsoleContext` can be in any `connection state` when this method is called.

  - ### addContextPropertyChangeListener

    public final void addContextPropertyChangeListener(PropertyChangeListener listener)
    Adds a `PropertyChangeListener` to the `JConsoleContext` object for this plugin. This method is a convenient method for this plugin to register a listener when the `JConsoleContext` object may or may not be available.

    For example, a plugin constructor can call this method to register a listener to listen to the `connectionState` property changes and the listener will be added to the `JConsoleContext` object when it is available.

    Parameters:
      `listener` - The `PropertyChangeListener` to be added
    Throws:
      `NullPointerException` - if `listener` is `null`.

  - ### removeContextPropertyChangeListener

    public final void removeContextPropertyChangeListener(PropertyChangeListener listener)
    Removes a `PropertyChangeListener` from the listener list of the `JConsoleContext` object for this plugin. If `listener` was never added, no exception is thrown and no action is taken.
    Parameters:
      `listener` - the `PropertyChangeListener` to be removed
    Throws:
      `NullPointerException` - if `listener` is `null`.