gnu.cajo.invoke

Class Client

java.lang.Object

java.awt.Component

java.awt.Container

java.awt.Panel

java.applet.Applet

gnu.cajo.invoke.Client

All Implemented Interfaces:

ImageObserver, MenuContainer, Serializable, Accessible

public final class Client
extends Applet

This class is used to create a hosting VM to receive a graphical proxy object, from a remote VM. The client will require one outbound port, on which to commuinicate with its proxy server and one on inbound, on which to receive asynchronous callbacks from the server. It will also require one short-term inbound port on which to receive the proxy class files. If the client is behind a firewall, these will have to be open.

Version:

1.0, 01-Nov-99 Initial release

Author:

John Catherino

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.applet.Applet

Applet.AccessibleApplet

Nested classes/interfaces inherited from class java.awt.Panel

Panel.AccessibleAWTPanel

Nested classes/interfaces inherited from class java.awt.Container

Container.AccessibleAWTContainer

Nested classes/interfaces inherited from class java.awt.Component

Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy

Field Summary

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

Constructors

Constructor and Description
Client() The default constructor does nothing.

Method Summary

Methods

Modifier and Type	Method and Description
void	destroy() This method is called from the AppleContext, when the applet is being disposed.
static Frame	frame(Component component, String title) This method is used by items to create a frame containing the AWT or Swing component.
String	getAppletInfo() This method provides the standard mechanism to identify this applet.
String[][]	getParameterInfo() When running as an applet, this method describes the optional client parameters.
void	init() When running as an applet, this method will connect back to its hosting server and request the item from the server's rmiregistry.
static void	main(String[] args) The application creates a graphical proxy hosting VM.
void	start() This method is called from the AppleContext, each time the applet becomes visible.
void	stop() This method is called from the AppleContext, each time the applet becomes invisible.
void	update(Graphics g) The update method double buffers the applet's paint method, to reduce flicker from the default background repainting.

Methods inherited from class java.applet.Applet

getAccessibleContext, getAppletContext, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, isActive, isValidateRoot, newAudioClip, play, play, resize, resize, setStub, showStatus

Methods inherited from class java.awt.Panel

addNotify

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, addImpl, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getInsets, getLayout, getListeners, getMaximumSize, getMinimumSize, getMousePosition, getPreferredSize, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paint, paintComponents, paramString, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, removeNotify, setComponentZOrder, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setFont, setLayout, transferFocusDownCycle, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocation, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeysEnabled, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle

Methods inherited from class java.lang.Object

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

Constructor Detail

Client

public Client()

The default constructor does nothing. Initialization is done when the applet is loaded into the browser, or when it is instantiated as an application.

Method Detail

getAppletInfo

public String getAppletInfo()

This method provides the standard mechanism to identify this applet.

Overrides:

getAppletInfo in class Applet

Returns:

The identification string for this applet.

getParameterInfo

public String[][] getParameterInfo()

When running as an applet, this method describes the optional client parameters. There are five such parameters which can be specified:

• The proxyName parameter is the name of the proxy server item registered in the server's rmiregistry. Unspecified it will be "main".
• The proxyPort parameter is the outbound port number on which to contact the proxy server. Unspecified it will be 1099. If the client is operating behind a firewall, the must be a permitted outbound port.
• The clientHost parameter is the external domain name or IP address the server must use to callback its proxy. It may need to be specified if the client is operating behind a NAT router. Unspecified it will be the client's default host address.
• The clientPort parameter is the external inbound port number on which the server can contact its proxy. It may need to be specified if the client is behind NAT, to map to the correct local port. If a firewall is being used, it must be a permitted inbound port. Unspecified, it will be the same as the local port value below.
• The localPort parameter is the internal inbound port number on which the server can contact its proxy. It may need to be specified if the client is behind NAT, to map to the correct remote port. Unspecified, it will be anonymous.

Overrides:

getParameterInfo in class Applet

Returns:

The parameter / information array.

init

public void init()

When running as an applet, this method will connect back to its hosting server and request the item from the server's rmiregistry. Next it will invoke a getProxy(null) on the remote reference to request its proxy item. If the item returns the proxy in a MarshalledObject, it will be extracted automatically. If the returned object is a proxy, the client will invoke its init method, passing it a remote reference itself, and to obtain its primary graphical representation, which will then be added into the applet's panel. The proxy can pass its remote reference back to its hosting item, or to other remote items, on which they can asynchronously call it back.

Overrides:

init in class Applet

start

public void start()

This method is called from the AppleContext, each time the applet becomes visible. It will attempt to invoke a no-arg start method on the proxy, in the event that it supports one. Support of the method by the proxy is optional.

Overrides:

start in class Applet

stop

public void stop()

This method is called from the AppleContext, each time the applet becomes invisible. It will attempt to invoke a no-arg stot method on the proxy, in the event that it supports one. Support of the method by the proxy is optional.

Overrides:

stop in class Applet

destroy

public void destroy()

This method is called from the AppleContext, when the applet is being disposed. It will attempt to invoke a no-arg destroy method on the proxy, in the event that it supports one. Support of the method by the proxy is optional.

Overrides:

destroy in class Applet

update

public void update(Graphics g)

The update method double buffers the applet's paint method, to reduce flicker from the default background repainting.

Overrides:

update in class Container

frame

public static Frame frame(Component component,
          String title)

This method is used by items to create a frame containing the AWT or Swing component. If the component implements WindowListener, it will be added to its display frame, before being made visible. For AWT components, the frame will be automatically double buffered, for JComponents.

Parameters:

component - The AWT/Swing component, typically returned from a proxy initialization, to be framed.

Returns:

the AWT Frame or Swing JFrame containing the component, already visible.

main

public static void main(String[] args)
                 throws Exception

The application creates a graphical proxy hosting VM. With the URL argument provided, it will use the static getItem method of the Remote class to contact the server. It will then invoke a null-argument getProxy on the resulting reference to request the primary proxy object of the item. If the proxy is a Swing JComponent, it will be displayed in a JFrame. If it is an AWT Component, it will be displayed in a Frame.

When using Client from the command line, it is possible to set the Client frame explicitly. To do this, simply type:

java -cp cajo.jar -Dgnu.cajo.invoke.Client.title="My Frame Title" gnu.cajo.invoke.Client //myHost:1198/test

Note: When running as an application (except via WebStart) it will load a NoSecurityManager, therefore, if no external SecurityManager is specified in the startup command line; the arriving proxies will have full permissions on this machine!

To restrict client proxies permissions, use a startup invocation similar to the following:

java -cp cajo.jar -Djava.security.manager -Djava.security.policy=client.policy ... gnu.cajo.invoke.Client ...

See the project client documentation, for more details.

The startup can take up to five additional optional configuration parameters, in this order:

• args[0] - The URL where to get the graphical proxy item:
  file:// http:// ftp:// ..., //host:port/name (rmiregistry), /path/name (serialized), or path/name (class).
  If unspecified, a graphical loader utility will be launched.
• args[1] - The optional external client port number, if using NAT.
• args[2] - The optional external client host name, if using NAT.
• args[3] - The optional internal client port number, if using NAT.
• args[4] - The optional internal client host name, if multi home/NIC.

Throws:

Exception