wt.util
Class WTContext

java.lang.Object
  java.util.Dictionary<K,V>
      java.util.Hashtable
          wt.util.WTContext

All Implemented Interfaces:

AppletContext, AppletStub, Serializable, Cloneable, Map

public class WTContext
extends Hashtable
implements AppletStub, AppletContext

This class holds static state partitioned by applet or application instance. It is a specialized Hashtable for accessing static state via thread groups which correspond to applet or application instances.

This class is useful when there is a need for semi-global static state partitioned by applet or application. Using Java static fields is insufficient for this purpose since a class loaded from the local class path will share static state among applets from all codebases, and even classes loaded from a remote codebase may share static state between multiple applets from that codebase.

During applet initialization or application startup, a call to WTContext.init associates the calling thread group to a WTContext object and stores associated application arguments or the applet instance as part of the context. Later, static access is provided by looking up the applicable WTContext object according to the current thread's thread group.

This class implements the AppletStub and AppletContext interfaces to provide uniform access to these methods in the context of both applications and applets. It also enables applets to be treated as reusable components by allowing a parent applet or application context to be used as the stub for a new child applet instance.

This class includes applet start, stop, and destroy methods which can be used to invoke the corresponding methods on all registered listeners. applets should use these methods so that any child applets or frames that are registered as listeners can respond to these methods accordingly.

Since untrusted applets cannot set a default locale, this class also has convenience methods for setting and retrieving a Locale object associated with a WTContext object. Applets that wish to use a non-default locale should call setLocale with the desired Locale object, and any code that wishes to use this non-default locale can call getLocale to retrieve the locale that applies to their context. Likewise, similar methods are available to associate a timezone with a context.

This class also has convenience methods for loading class files and opening class resource files using the applicable applet class loader and URL connections. These methods should be used when classes which may have been loaded from the local classpath need to dynamically load additional classes or open resource files which may not reside in the local class path. For example, if core classes are deployed in the local class path, but an applet class is loaded from a Web server, any calls to Class.forName in the locally loaded classes will not find classes or files associated with the applet that do not also exist in the local class path.

Some Windchill classes perform static class initialization based on local properties obtained from the WTProperties class. Therefore, the WTContext.init method will implicitly call WTProperties.getLocalProperties to guarantee that the local properties will be available. If not, an ExceptionInInitializerError is thrown to abort application or applet startup. This is a safety measure since it is unlikely that static class initialization errors will be handled gracefully later on.

Example application main:

 public static void main (String args)
 {
    // Initialize WTContext with command line arguments
    WTContext.init(args);

    // Do application stuff
    ...
 }
 

Example applet init:

public void init ()
 {
    // Initialize WTContext for this applet
    WTContext.init(this);

    // Do applet init stuff
    ...
 }

 public void destroy ()
 {
    // Destroy WTContext for this applet
    WTContext.getContext(this).destroy(this);
 }
 

If context sensitive operations are performed from a thread group that does not map to an initialized context, it may be necessary to temporarily force mapping of the current thread to the desired context's thread group. The setContext and setContextGroup methods exist for this purpose.

In Microsoft's Internet Explorer browser, Java's AWT event dispatching may take place in a thread group that is shared by multiple applet contexts. The following example illustrates explicitly setting context in a actionPerformed method:

 public void actionPerformed (ActionEvent e)
 {
    try
    {
       // Set context to parent applet while processing
       WTContext.setContext(applet);

       // Do action stuff
       ...
    }
    finally
    {
       WTContext.setContext((applet)null);
    }
 }
 

If not explicitly set, context lookup will fail over to any context corresponding to a child thread group of the current group. If none is found, a new empty context is implicitly created. This failover behavior is intended for fault tolerance in single-user applications or web browsers. It can be explicitly controlled in multi-user applications using the setLookupTolerance method.

NOTE: For performance of context lookup, nested context's are not supported. Stand alone applications usually have a single context, and applets should have one context per applet thread group created by the browser. If an application wants to manage multiple contexts for different thread groups, the application initialization methods should be called with a null argument array rather than calling the application initialization method with command line arguments. This is because the application initialization method creates a context that applies to the highest parent thread group reachable when it is called with the command line arguments. If an application starts out with a single context, but later wishes to transform into a container of multiple contexts, the initial context should be destroyed to break this high level thread group association.

Supported API: true
Extendable false

See Also:

WTProperties, Serialized Form

Method Summary

void	addAppletListener(Applet listener) Add a Applet to the AppletListener list.
void	addAppletListener(AppletListener listener) Add a AppletListener to the listener list.
static void	addGlobalAppletListener(AppletListener listener) Add a global AppletListener to the listener list.
void	addPropertyChangeListener(PropertyChangeListener listener) Add a PropertyChangeListener to the listener list.
void	appletResize(int width, int height) Called when the applet wants to be resized.
static ThreadGroup	currentThreadGroup() Get the current thread group of the calling thread.
void	destroy() Destroy this WTContext object.
void	destroy(Applet applet) Destroy this WTContext only if the given Applet object is the parent Applet for this context.
static WTContext	findContext(Component component) Find the WTContext object currently associated with the given component's top-most parent applet.
static WTContext	findContext(ThreadGroup group) Find the WTContext object currently associated with the given thread group.
Applet	getApplet() Get the applet corresponding to this context.
Applet	getApplet(String name) Finds and returns the applet in the document represented by this applet context with the given name.
AppletContext	getAppletContext() Gets a handler to the applet's context.
Enumeration	getApplets() Finds all the applets in the document represented by this applet context.
String[]	getArgs() Get the argument array for this context.
AudioClip	getAudioClip(String name) Creates an audio clip from a resource file.
AudioClip	getAudioClip(URL url) Creates an audio clip.
ClassLoader	getClassLoader() Returns the Class loader of this context's top-most applet.
URL	getCodeBase() Gets the base URL.
static WTContext	getContext() Get the WTContext object associated with the current thread group.
static WTContext	getContext(Component component) Get the WTContext object currently associated with the given component's top-most parent applet.
static WTContext	getContext(ThreadGroup group) Get the WTContext object currently associated with the given thread group.
static ThreadGroup	getContextGroup() Return WTContext thread group associated with the current thread.
URL	getDocumentBase() Gets the document URL.
Image	getImage(String name) Get an image from a resource file.
Image	getImage(URL url) Returns an Image object that can then be painted on the screen.
Locale	getLocale() Get locale for this context.
String	getParameter(String name) Returns the value of the named parameter in the HTML tag.
Frame	getParentFrame() Get the parent frame for this context.
URL	getResource(String name) Find a resource with a given a name.
URL	getResource(URL codebase, String name) Find a resource with a given a name.
InputStream	getResourceAsStream(Class cls, String name) Get an InputStream for a given resource name after applying a naming convention based on the supplied class name: if the resource name starts with "/", it is used as is.
InputStream	getResourceAsStream(String name) Get an InputStream for a given resource name.
InputStream	getResourceAsStream(String name, URL[] url) Get an InputStream for a given resource name.
InputStream	getResourceAsStream(URL codebase, String name) Get an InputStream for a given resource name by opening a URL connection relative to the given codebase.
URL	getServerResource(String name) Find a server resource with a given name.
InputStream	getServerResourceAsStream(String name) Get an InputStream for a given server resource name by opening a URL connection relative to this context's codebase.
InputStream	getStream(String key) Returns the stream to which specified key is associated within this context.
Iterator	getStreamKeys() Finds all the keys of the streams in this context.
Clipboard	getSystemClipboard() Get the system clipboard.
InputStream	getSystemResourceAsStream(String name) Get an InputStream for a given system resource name.
ThreadGroup	getThreadGroup() Get the thread group corresponding to this context.
TimeZone	getTimeZone() Get time zone for this context.
static void	init(Component component) Initialize WTContext for an applet or applet component.
static void	init(String[] args) Initialize WTContext for an application.
static void	init(String[] args, boolean local_resources_only) Initialize WTContext for a server application.
void	interrupt() Interrupt all active threads in this context's thread group and its subgroups.
boolean	isActive() Determines if the applet is active.
Class	loadClass(String name) Returns the Class object associated with the class with the given string name.
Object	put(Object key, Object value) Override Hashtable.put to add property change support.
Object	remove(Object key) Override Hashtable.remove to add property change support.
void	removeAppletListener(Applet listener) Remove a Applet from the AppletListener list.
void	removeAppletListener(AppletListener listener) Remove a AppletListener from the listener list.
static void	removeGlobalAppletListener(AppletListener listener) Remove a global AppletListener from the listener list.
void	removePropertyChangeListener(PropertyChangeListener listener) Remove a PropertyChangeListener from the listener list.
static void	setContext(Component component) Temporarily set the WTContext object associated with the current thread to the WTContext object associated with the given component's top-most parent applet.
static void	setContextGroup(ThreadGroup group) Temporarily set the WTContext object associated with the current thread to the one associated with the given thread group.
static void	setDefaultTimeZone(TimeZone timezone) Set default time zone.
static void	setLenientLookup(boolean lenient) Set whether context lookup should be lenient with respect to context initialization.
void	setLocale(Locale locale) Set locale for this context.
void	setParentFrame(Frame parent_frame) Set the parent frame for this context.
void	setStream(String key, InputStream stream) Associates the specified stream with the specified key in this context.
void	setTimeZone(TimeZone timezone) Set time zone for this context.
static void	setVerbose(boolean verbose) Set verbose mode for debugging.
void	showDocument(URL url) Replaces the Web page currently being viewed with the given URL.
void	showDocument(URL url, String target) Requests that the browser or applet viewer show the Web page indicated by the url argument.
void	showStatus(String status) Requests that the argument string be displayed in the "status window".
void	start() Report a Applet.start call to any registered listeners.
void	start(Applet applet) Report a Applet.start call to any registered listeners only if the given Applet object is the parent Applet for this context.
void	stop() Report a Applet.stop call to any registered listeners.
void	stop(Applet applet) Report a Applet.stop call to any registered listeners only if the given Applet object is the parent Applet for this context.
boolean	useLocalResourcesOnly() Return whether local resources should be used as server resources for this context.

Methods inherited from class java.util.Hashtable

clear, clone, contains, containsKey, containsValue, elements, entrySet, equals, get, hashCode, isEmpty, keys, keySet, putAll, rehash, size, toString, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

init

public static void init(String[] args)

Initialize WTContext for an application. Associates a context having the given argument array with the top-most parent thread group of the current thread group.

Supported API: true

Parameters:

args - the args array passed to the application's main method.

init

public static void init(String[] args,
                        boolean local_resources_only)

Initialize WTContext for a server application. Associates a context having the given argument array with the top-most parent thread group of the current thread group. If local_resources_only is true, this is a server application for which server resources are available as local (class path) resources. Server resources for a context are otherwise accessed using URLs relative to the server codebase as determined by the wt.util.WTProperties class.

Supported API: true

Parameters:

args - the args array passed to the applicaion's main method.

local_resources_only - use local resources as server resources

See Also:

WTProperties

init

public static void init(Component component)

Initialize WTContext for an applet or applet component. This associates the given component's top-most parent Applet with the current thread group. A corresponding call to destroy should be called when the applet is destroyed to guarantee timely garbage collection of the Applet object.

If a context already exist for the current thread group and there is already an applet associated with that context, this call is ignored.

Supported API: true

Parameters:

component - the Applet or Component object

See Also:

destroy()

destroy

public void destroy()

Destroy this WTContext object. This should be called to guarantee timely garbage collection of objects referenced by the WTContext object. If not called, the objects will remain referenced until a new WTContext object is created, at which time the WTContext class will automatically destroy contexts associated with destroyed thread groups.

Any registered AppletListener objects will be informed about of this destroy call.

Applets should call the version of this method that accepts an Applet argument to guarantee that this context is only destroyed if the Applet object is the parent Applet for this context.

Supported API: true

See Also:

init(java.lang.String[]), addAppletListener(wt.util.AppletListener)

destroy

public void destroy(Applet applet)

Destroy this WTContext only if the given Applet object is the parent Applet for this context.

Supported API: true

See Also:

init(java.lang.String[])

getContext

public static WTContext getContext()

Get the WTContext object associated with the current thread group. If no association has been created by an explicit call to init or setContext, then an empty context is created.

Supported API: true

Returns:

the current WTContext object

See Also:

init(java.lang.String[])

getContext

public static WTContext getContext(ThreadGroup group)

Get the WTContext object currently associated with the given thread group. If no context exists for the given thread group, an empty context is created.

Supported API: true

Returns:

the WTContext object

See Also:

init(java.lang.String[])

findContext

public static WTContext findContext(ThreadGroup group)

Find the WTContext object currently associated with the given thread group.

Supported API: true

Parameters:

group - the thread group

Returns:

the current WTContext object or null if none

See Also:

init(java.lang.String[])

getContext

public static WTContext getContext(Component component)

Get the WTContext object currently associated with the given component's top-most parent applet. If the given component does not have a parent applet or if no context is currently associated with the applet, the current thread group's context is returned.

Supported API: true

Parameters:

component - the Component object

Returns:

the WTContext object

See Also:

init(java.lang.String[])

findContext

public static WTContext findContext(Component component)

Find the WTContext object currently associated with the given component's top-most parent applet. If the given component does not have a parent applet or if no context is currently associated with the applet, null is returned.

Supported API: true

Parameters:

component - the Component object

Returns:

the current WTContext object or null if none

See Also:

init(java.lang.String[])

setContext

public static void setContext(Component component)

Temporarily set the WTContext object associated with the current thread to the WTContext object associated with the given component's top-most parent applet. If the given component does not have a parent applet or if no context is currently associated with the applet, the call is ignored.

This method is typically called within the AWT event dispatching thread which may be executing in a thread group that is a parent of multiple applet thread groups (e.g. IE4.0). It should be used in a try/finally block to reset the association to null when processing for the given component is complete.

Supported API: true

Parameters:

component - the Component object

See Also:

init(java.lang.String[])

setContextGroup

public static void setContextGroup(ThreadGroup group)

Temporarily set the WTContext object associated with the current thread to the one associated with the given thread group.

This method can be used by an application which explicitly manages thread groups with different contexts. It should be used in a try/finally block to reset the association to the previous value or null when processing is complete.

Supported API: true

Parameters:

group - the ThreadGroup object

See Also:

init(java.lang.String[]), getContextGroup()

getContextGroup

public static ThreadGroup getContextGroup()

Return WTContext thread group associated with the current thread. Returns null if no explicit association has been set using setContextGroup.

Supported API: true

Returns:

the current mapping or null if none

See Also:

setContextGroup(java.lang.ThreadGroup)

getArgs

public String[] getArgs()

Get the argument array for this context. Returns the argument array that was specified when init was called for this context. If no argument array was specified, or it was null, an empty array is returned. This allows the return to be treated just like the argument array passed to an application's main method, which is never null.

Supported API: true

Returns:

the argument array

See Also:

init(java.lang.String[])

getApplet

public Applet getApplet()

Get the applet corresponding to this context. Returns the Applet object associated with this context when it was initialized. If no applet is associated with this context, null is returned.

Supported API: true

Returns:

the Applet object

See Also:

init(java.lang.String[])

getParentFrame

public Frame getParentFrame()

Get the parent frame for this context. A parent frame is useful for displaying modal dialogs, but objects that are not part of a component containment hierarchy need a way obtain a frame reference. This method returns the frame set by a call to setParentFrame. If no parent frame has been explicitly set for this context, the parent frame of the applet associated with this context is returned. If no applet is associated with this context, or it is not currently contained in a frame, null is returned.

Supported API: true

Returns:

the parent frame

See Also:

init(java.lang.String[])

setParentFrame

public void setParentFrame(Frame parent_frame)

Set the parent frame for this context.

Supported API: true

See Also:

init(java.lang.String[])

getThreadGroup

public ThreadGroup getThreadGroup()

Get the thread group corresponding to this context. Returns the ThreadGroup associated with this context when it was initialized.

Supported API: true

Returns:

the ThreadGroup object

See Also:

init(java.lang.String[])

currentThreadGroup

public static ThreadGroup currentThreadGroup()

Get the current thread group of the calling thread. First checks to see if the currentThread has been mapped to a specific thread group and if so returns the mapped thread group. This mapping occurs through calls to setContext or setContextGroup. Otherwise, if a security manager is present, it is called to get the thread group into which any new thread being constructed in this thread would be assigned. By default, it returns the thread group of the current thread, but this could be overriden by specific security manager to return the appropriate thread group if called from within a system thread. If no security manager is present, the current thread's thread group is returned.

Supported API: true

Returns:

the ThreadGroup object

setVerbose

public static void setVerbose(boolean verbose)

Set verbose mode for debugging. When true, this class will display trace messages when contexts are created or destroyed and when resources are being loaded via the WTContext class.

Supported API: true

Parameters:

verbose - the verbose setting

interrupt

public void interrupt()

Interrupt all active threads in this context's thread group and its subgroups. The calling thread, if included, is not interrupted.

Note: a bug in JDK 1.1 prevents applications from terminating properly if their main thread is interrupted, even after the run method has returned. Therefore, all threads named "main" are also skipped.

Supported API: true

useLocalResourcesOnly

public boolean useLocalResourcesOnly()

Return whether local resources should be used as server resources for this context.

Supported API: true

Returns:

the local_resources_only flag used on the init method.

setLenientLookup

public static void setLenientLookup(boolean lenient)

Set whether context lookup should be lenient with respect to context initialization. When true (default), lookup for a thread group that does not correspond to an initialized context will fail over to any context initialized for a child thread group. Applications managing multiple contexts for different users may wish to disable this fault tolerance since it may lead to unexpected context sharing. Implicit creation of contexts is still allowed, but only if there is no context already initialized for a child thread group (which would result in nested contexts, which are not allowed).

Supported API: true

Parameters:

lenient -

addPropertyChangeListener

public void addPropertyChangeListener(PropertyChangeListener listener)

Add a PropertyChangeListener to the listener list. Property change events will be fired to all registered listeners whenever a value in this hashtable is added, changed, or removed.

Supported API: true

Parameters:

listener - the PropertyChangeListener to be added

removePropertyChangeListener

public void removePropertyChangeListener(PropertyChangeListener listener)

Remove a PropertyChangeListener from the listener list.

Supported API: true

Parameters:

listener - the PropertyChangeListener to be removed

put

public Object put(Object key,
                  Object value)

Override Hashtable.put to add property change support.

Supported API: true

Specified by:

put in interface Map

Overrides:

put in class Hashtable

Parameters:

key - the hashtable key

value - the value

Returns:

the previous value of the specified key in this hashtable, or null if it did not have one.

See Also:

Hashtable

remove

public Object remove(Object key)

Override Hashtable.remove to add property change support.

Supported API: true

Specified by:

remove in interface Map

Overrides:

remove in class Hashtable

Parameters:

key - the key that needs to be removed

Returns:

the value to which the key had been mapped in this hashtable, or null if the key did not have a mapping.

See Also:

Hashtable

addAppletListener

public void addAppletListener(AppletListener listener)

Add a AppletListener to the listener list.

Supported API: true

Parameters:

listener - the AppletListener to be added

addAppletListener

public void addAppletListener(Applet listener)

Add a Applet to the AppletListener list. This method allows child applets to be listeners without declaring that they implement the AppletListener interface.

Supported API: true

Parameters:

listener - the Applet to be added

removeAppletListener

public void removeAppletListener(AppletListener listener)

Remove a AppletListener from the listener list.

Supported API: true

Parameters:

listener - The AppletListener to be removed

removeAppletListener

public void removeAppletListener(Applet listener)

Remove a Applet from the AppletListener list.

Supported API: true

Parameters:

listener - The Applet to be removed

addGlobalAppletListener

public static void addGlobalAppletListener(AppletListener listener)

Add a global AppletListener to the listener list. Global listeners will receive AppletListener calls for all contexts. Application code may issue a WTContext.stop() to signal a panic shutdown. This method allows adding a single listener within applications that may have multiple multi contexts active simultaneously.

Supported API: true

Parameters:

listener - the AppletListener to be added

removeGlobalAppletListener

public static void removeGlobalAppletListener(AppletListener listener)

Remove a global AppletListener from the listener list.

Supported API: true

Parameters:

listener - The AppletListener to be removed

start

public void start()

Report a Applet.start call to any registered listeners.

Supported API: true

start

public void start(Applet applet)

Report a Applet.start call to any registered listeners only if the given Applet object is the parent Applet for this context.

Supported API: true

See Also:

init(java.lang.String[])

stop

public void stop()

Report a Applet.stop call to any registered listeners.

Supported API: true

stop

public void stop(Applet applet)

Report a Applet.stop call to any registered listeners only if the given Applet object is the parent Applet for this context.

Supported API: true

See Also:

init(java.lang.String[])

isActive

public boolean isActive()

Determines if the applet is active. An applet is active just before its start method is called. It becomes inactive immediately after its stop method is called.

Supported API: true

Specified by:

isActive in interface AppletStub

Returns:

true if the applet is active; false otherwise.

getDocumentBase

public URL getDocumentBase()

Gets the document URL.

Supported API: true

Specified by:

getDocumentBase in interface AppletStub

Returns:

the URL of the document containing the applet.

getCodeBase

public URL getCodeBase()

Gets the base URL.

Supported API: true

Specified by:

getCodeBase in interface AppletStub

Returns:

the URL of the applet.

getParameter

public String getParameter(String name)

Returns the value of the named parameter in the HTML tag. For example, if an applet is specified as

<applet code="Clock" width=50 height=50>
<param name=Color value="blue">
</applet>

then a call to getParameter("Color") returns the value "blue".

Supported API: true

Specified by:

getParameter in interface AppletStub

Parameters:

name - a parameter name.

Returns:

the value of the named parameter.

getAppletContext

public AppletContext getAppletContext()

Gets a handler to the applet's context.

Supported API: true

Specified by:

getAppletContext in interface AppletStub

Returns:

the applet's context.

appletResize

public void appletResize(int width,
                         int height)

Called when the applet wants to be resized.

Supported API: true

Specified by:

appletResize in interface AppletStub

Parameters:

width - the new requested width for the applet.

height - the new requested height for the applet.

getAudioClip

public AudioClip getAudioClip(URL url)

Creates an audio clip.

Supported API: true

Specified by:

getAudioClip in interface AppletContext

Parameters:

url - an absolute URL giving the location of the audio clip.

Returns:

the audio clip at the specified URL.

getAudioClip

public AudioClip getAudioClip(String name)

Creates an audio clip from a resource file.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

Returns:

the audio clip

getImage

public Image getImage(URL url)

Returns an Image object that can then be painted on the screen. The url argument that is passed as an argument must specify an absolute URL.

This method always returns immediately, whether or not the image exists. When the applet attempts to draw the image on the screen, the data will be loaded. The graphics primitives that draw the image will incrementally paint on the screen.

Supported API: true

Specified by:

getImage in interface AppletContext

Parameters:

url - an absolute URL giving the location of the image.

Returns:

the image at the specified URL.

See Also:

Image

getImage

public Image getImage(String name)

Get an image from a resource file. For resources with corresponding HTTP or FILE URLs, the normal getImage method is called. For system resources, the resource is loaded into a byte array and converted to an image from there. This is due to problems Netscape and Microsoft VMs have dealing with system resource URLs.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

Returns:

the image

See Also:

Image

getApplet

public Applet getApplet(String name)

Finds and returns the applet in the document represented by this applet context with the given name. The name can be set in the HTML tag by setting the name attribute.

Supported API: true

Specified by:

getApplet in interface AppletContext

Parameters:

name - an applet name.

Returns:

the applet with the given name, or null if not found.

getApplets

public Enumeration getApplets()

Finds all the applets in the document represented by this applet context.

Supported API: true

Specified by:

getApplets in interface AppletContext

Returns:

an enumeration of all applets in the document represented by this applet context.

showDocument

public void showDocument(URL url)

Replaces the Web page currently being viewed with the given URL. If this context has an applet, it is passed to the applet context's showDocument method. If this context is an application and can execute commands, an attempt is made to launch a browser to view the page. On Windows platforms this is done using rundll32.exe to open the URL in the user's default browser. On unix, this is done by trying to execute netscape. To allow the commands to be configured, a property named wt.context.showDocument. can be set where os_name is the value of the os.name Java system property with any space characters replaced by underscore. The value is a MessageFormat pattern where "{0}" will be replaced by the URL. If the value contains more than one command separated by newline, each line is executed until one finishes without writing anything to stderr.

Supported API: true

Specified by:

showDocument in interface AppletContext

Parameters:

url - an absolute URL giving the location of the document.

showDocument

public void showDocument(URL url,
                         String target)

Requests that the browser or applet viewer show the Web page indicated by the url argument. The target argument indicates where to display the frame. The target argument is interpreted as follows:

"_self"	show in the current frame
"_parent"	show in the parent frame
"_top"	show in the topmost frame
"_blank"	show in a new unnamed top-level window
name	show in a new top-level window named name

An applet viewer or browser is free to ignore showDocument.

Supported API: true

Specified by:

showDocument in interface AppletContext

Parameters:

url - an absolute URL giving the location of the document.

target - a String indicating where to display the page.

showStatus

public void showStatus(String status)

Requests that the argument string be displayed in the "status window". Many browsers and applet viewers provide such a window, where the application can inform users of its current state.

Supported API: true

Specified by:

showStatus in interface AppletContext

Parameters:

status - a string to display in the status window.

setStream

public void setStream(String key,
                      InputStream stream)
               throws IOException

Associates the specified stream with the specified key in this context. If the context previously contained a mapping for this key, the old value is replaced.

Supported API: true

Specified by:

setStream in interface AppletContext

Parameters:

key - key with which the specified value is to be associated.

stream - stream to be associated with the specified key. If this parameter is null, the specified key is removed in this context.

Throws:

IOException - if the stream size exceeds a size limit. For applets this is determined by applet's implementation; for applications, this is 65536 bytes.

getStream

public InputStream getStream(String key)

Returns the stream to which specified key is associated within this context. Returns null if the context contains no stream for this key.

Supported API: true

Specified by:

getStream in interface AppletContext

Parameters:

key - key with which the specified value is to be associated.

Returns:

the stream to which this context maps the key.

getStreamKeys

public Iterator getStreamKeys()

Finds all the keys of the streams in this context.

Supported API: true

Specified by:

getStreamKeys in interface AppletContext

Returns:

an Iterator of all the names of the streams in this context.

setLocale

public void setLocale(Locale locale)

Set locale for this context. Setting to null returns the locale to the default returned by Locale.getDefault. If this context corresponds to an applet, the applet's locale is set so it can affect the getLocale method of components contained in the applet.

Supported API: true

Parameters:

locale - the Locale object

getLocale

public Locale getLocale()

Get locale for this context. If locale has not been explicitly set using setLocale, the locale defined by a parameter named wt.context.locale is returned. If this parameter is not set, then the default locale returned by the context's applet or by Locale.getDefault is returned.

Supported API: true

Returns:

the Locale object

setTimeZone

public void setTimeZone(TimeZone timezone)

Set time zone for this context. Setting to null returns the time zone to the default.

Supported API: true

Parameters:

timezone - the TimeZone object

setDefaultTimeZone

public static void setDefaultTimeZone(TimeZone timezone)

Set default time zone. Setting to null returns the time zone to the default returned by TimeZone.getDefault.

Supported API: true

Parameters:

timezone - the TimeZone object

getTimeZone

public TimeZone getTimeZone()

Get time zone for this context. If time zone has not been explicitly set using setTimeZone, the default time zone is returned.

Supported API: true

Returns:

the TimeZone object

getClassLoader

public ClassLoader getClassLoader()

Returns the Class loader of this context's top-most applet.

Supported API: true

loadClass

public Class loadClass(String name)
                throws ClassNotFoundException

Returns the Class object associated with the class with the given string name. Given the fully-qualified name for a class or interface, this method attempts to locate, load and link the class. This method delegates to the class loader of this context's top-most applet.

Supported API: true

Throws:

ClassNotFoundException - if context's class loader can't find the class file

getSystemResourceAsStream

public InputStream getSystemResourceAsStream(String name)

Get an InputStream for a given system resource name. This is similar to ClassLoader.getSystemResourceAsStream but attempts to work around Netscape security exceptions. Returns null if no resource by this name is found. The returned InputStream is buffered if necessary for reading efficiency.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

url - a single element URL array to receive the URL corresponding to the stream

Returns:

an InputStream for the resource, or null if not found

getResourceAsStream

public InputStream getResourceAsStream(String name)

Get an InputStream for a given resource name. If the WTContext class was loaded from the local class path, this method first attempts to open the resource as a local system resource. If not found, or unable to access local resources due to security restrictions, this method delegates to the class loader of this context's top-most applet. If that class loader is unable to open the resource, a URL connection is attempted relative to this context's codebase. Null is returned if no resource by this name is found. The returned InputStream is buffered if necessary for reading efficiency.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

url - a single element URL array to receive the URL corresponding to the stream

Returns:

an InputStream for the resource, or null if not found

getResourceAsStream

public InputStream getResourceAsStream(String name,
                                       URL[] url)

Get an InputStream for a given resource name. If the WTContext class was loaded from the local class path, this method first attempts to open the resource as a local system resource. If not found, or unable to access local resources due to security restrictions, this method delegates to the class loader of this context's top-most applet. If that class loader is unable to open the resource, a URL connection is attempted relative to this context's codebase. Null is returned if no resource by this name is found. The returned InputStream is buffered if necessary for reading efficiency.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

url - a single element URL array to receive the URL corresponding to the stream

Returns:

an InputStream for the resource, or null if not found

getResourceAsStream

public InputStream getResourceAsStream(Class cls,
                                       String name)

Get an InputStream for a given resource name after applying a naming convention based on the supplied class name: if the resource name starts with "/", it is used as is. Otherwise, the name of the class's package is prepended, after converting "." to "/". This method first attempts to open the resource as a local system resource. If not found, or unable to access local resources due to security restrictions, this method delegates to the class loader of this context's top-most applet. If that class loader is unable to open the resource, a URL connection is attempted relative to this context's codebase. Null is returned if no resource by this name is found. The returned InputStream is buffered if necessary for reading efficiency.

Supported API: true

Parameters:

cls - the class to fully qualify relative resource names

name - the name of the resource (full path, may include leading "/")

Returns:

an InputStream for the resource, or null if not found

getResourceAsStream

public InputStream getResourceAsStream(URL codebase,
                                       String name)
                                throws IOException

Get an InputStream for a given resource name by opening a URL connection relative to the given codebase. This method could be static except for the need to use this context's Netscape security privileges. The returned InputStream is buffered if necessary for reading efficiency.

Supported API: true

Parameters:

codebase - the codebase URL

name - the name of the resource (full path, may include leading "/")

Returns:

an InputStream for the resource, or null if not found

Throws:

IOException

getResource

public URL getResource(String name)

Find a resource with a given a name. The return is a URL to the resource. Doing a getContent() on the URL may return an Image, an AudioClip, or an InputStream. The method delegates to the class loader of this context's top-most applet. If that class loader is unable to open the resource, a URL is built relative to this context's codebase.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

Returns:

a URL for the resource

getResource

public URL getResource(URL codebase,
                       String name)

Find a resource with a given a name. The return is a URL to the resource. This method builds a URL relative to a given codebase URL.

Supported API: true

Parameters:

codebase - the codebase URL

name - the name of the resource (full path, may include leading "/")

Returns:

a URL for the resource

getServerResourceAsStream

public InputStream getServerResourceAsStream(String name)

Get an InputStream for a given server resource name by opening a URL connection relative to this context's codebase. This is similar to getResourceAsStream but won't find resources in the local class path. The returned InputStream is buffered if necessary for reading efficiency.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

Returns:

an InputStream for the resource, or null if not found

getServerResource

public URL getServerResource(String name)

Find a server resource with a given name. The return is a URL to the resource. This method builds a URL relative to this context's server codebase. This is similar to getResource but doesn't return URLs to local class path resources.

Supported API: true

Parameters:

name - the name of the resource (full path, may include leading "/")

Returns:

a URL for the resource

getSystemClipboard

public Clipboard getSystemClipboard()

Get the system clipboard.

Supported API: true

Returns:

the system clipboard.