001    /* Applet.java -- Java base applet class
002       Copyright (C) 1999, 2002, 2004, 2005  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package java.applet;
040    
041    import java.awt.Component;
042    import java.awt.Dimension;
043    import java.awt.GraphicsEnvironment;
044    import java.awt.HeadlessException;
045    import java.awt.Image;
046    import java.awt.Panel;
047    import java.io.IOException;
048    import java.io.ObjectInputStream;
049    import java.net.MalformedURLException;
050    import java.net.URL;
051    import java.util.Locale;
052    
053    import javax.accessibility.AccessibleContext;
054    import javax.accessibility.AccessibleRole;
055    import javax.accessibility.AccessibleState;
056    import javax.accessibility.AccessibleStateSet;
057    import javax.sound.sampled.AudioSystem;
058    import javax.sound.sampled.Clip;
059    import javax.sound.sampled.LineUnavailableException;
060    import javax.sound.sampled.UnsupportedAudioFileException;
061    
062    /**
063     * This is the base applet class.  An applet is a Java program that
064     * runs inside a web browser or other applet viewer in a restricted
065     * environment.
066     *
067     * <p>To be useful, a subclass should override at least start(). Also useful
068     * are init, stop, and destroy for control purposes, and getAppletInfo and
069     * getParameterInfo for descriptive purposes.
070     *
071     * @author Aaron M. Renn (arenn@urbanophile.com)
072     * @author Eric Blake (ebb9@email.byu.edu)
073     * @since 1.0
074     * @status updated to 1.4
075     */
076    public class Applet extends Panel
077    {
078      /**
079       * Compatible with JDK 1.0+.
080       */
081      private static final long serialVersionUID = -5836846270535785031L;
082    
083      /** The applet stub for this applet. */
084      private transient AppletStub stub;
085    
086      /** Some applets call setSize in their constructors.  In that case,
087          these fields are used to store width and height values until a
088          stub is set. */
089      private transient int width;
090      private transient int height;
091    
092      /**
093       * The accessibility context for this applet.
094       *
095       * @serial the accessibleContext for this
096       * @since 1.2
097       */
098      private AccessibleContext accessibleContext;
099    
100      /**
101       * Default constructor for subclasses.
102       *
103       * @throws HeadlessException if in a headless environment
104       */
105      public Applet()
106      {
107        if (GraphicsEnvironment.isHeadless())
108          throw new HeadlessException();
109      }
110    
111      /**
112       * The browser calls this method to set the applet's stub, which is the
113       * low level interface to the browser. Manually setting this to null is
114       * asking for problems down the road.
115       *
116       * @param stub the applet stub for this applet
117       */
118      public final void setStub(AppletStub stub)
119      {
120        this.stub = stub;
121    
122        if (width != 0 && height != 0)
123          stub.appletResize (width, height);
124      }
125    
126      /**
127       * Tests whether or not this applet is currently active. An applet is active
128       * just before the browser invokes start(), and becomes inactive just
129       * before the browser invokes stop().
130       *
131       * @return <code>true</code> if this applet is active
132       */
133      public boolean isActive()
134      {
135        return stub.isActive();
136      }
137    
138      /**
139       * Returns the basename URL of the document this applet is embedded in. This
140       * is everything up to the final '/'.
141       *
142       * @return the URL of the document this applet is embedded in
143       * @see #getCodeBase()
144       */
145      public URL getDocumentBase()
146      {
147        return stub.getDocumentBase();
148      }
149    
150      /**
151       * Returns the URL of the code base for this applet.
152       *
153       * @return the URL of the code base for this applet
154       */
155      public URL getCodeBase()
156      {
157        return stub.getCodeBase();
158      }
159    
160      /**
161       * Returns the value of the specified parameter that was specified in
162       * the <code>&lt;APPLET&gt;</code> tag for this applet.
163       *
164       * @param name the parameter name
165       * @return the parameter value, or null if the parameter does not exist
166       * @throws NullPointerException if name is null
167       */
168      public String getParameter(String name)
169      {
170        return stub.getParameter(name);
171      }
172    
173      /**
174       * Returns the applet context for this applet.
175       *
176       * @return the applet context for this applet
177       */
178      public AppletContext getAppletContext()
179      {
180        return stub.getAppletContext();
181      }
182    
183      /**
184       * Requests that the applet window for this applet be resized.
185       *
186       * @param width the new width in pixels
187       * @param height the new height in pixels
188       */
189      public void resize(int width, int height)
190      {
191        if (stub == null)
192          {
193            this.width = width;
194            this.height = height;
195          }
196        else
197          stub.appletResize(width, height);
198      }
199    
200      /**
201       * Requests that the applet window for this applet be resized.
202       *
203       * @param dim the requested dimensions
204       * @throws NullPointerException if dim is null
205       */
206      public void resize(Dimension dim)
207      {
208        resize(dim.width, dim.height);
209      }
210    
211      /**
212       * Displays the specified message in the status window if that window
213       * exists.
214       *
215       * @param message the status message, may be null
216       */
217      public void showStatus(String message)
218      {
219        getAppletContext().showStatus(message);
220      }
221    
222      /**
223       * Returns an image from the specified URL.  Note that the image is not
224       * actually retrieved until the applet attempts to display it, so this
225       * method returns immediately.
226       *
227       * @param url the URL of the image
228       * @return the retrieved image
229       * @throws NullPointerException if url is null
230       */
231      public Image getImage(URL url)
232      {
233        return getAppletContext().getImage(url);
234      }
235    
236      /**
237       * Returns an image from the specified absolute URL, and relative path
238       * from that URL.  Note that the image is not actually retrieved until the
239       * applet attempts to display it, so this method returns immediately.
240       * This calls <code>getImage(new URL(url, name))</code>, but if building
241       * the new URL fails, this returns null.
242       *
243       * @param url the base URL of the image
244       * @param name the name of the image relative to the URL
245       * @return the retrieved image, or null on failure
246       * @see #getImage(URL)
247       */
248      public Image getImage(URL url, String name)
249      {
250        try
251          {
252            return getImage(new URL(url, name));
253          }
254        catch (MalformedURLException e)
255          {
256            return null;
257          }
258      }
259    
260      /**
261       * Returns an audio clip from the specified URL. This clip is not tied to
262       * any particular applet.
263       *
264       * @param url the URL of the audio clip
265       * @return the retrieved audio clip
266       * @throws NullPointerException if url is null
267       * @see #getAudioClip(URL)
268       * @since 1.2
269       */
270      public static final AudioClip newAudioClip(URL url)
271      {
272        return new URLAudioClip(url);
273      }
274    
275      /**
276       * Returns an audio clip from the specified URL. Note that the clip is not
277       * actually retrieved until the applet attempts to play it, so this method
278       * returns immediately.
279       *
280       * @param url the URL of the audio clip
281       * @return the retrieved audio clip
282       * @throws NullPointerException if url is null
283       */
284      public AudioClip getAudioClip(URL url)
285      {
286        return getAppletContext().getAudioClip(url);
287      }
288    
289      /**
290       * Returns an audio clip from the specified absolute URL, and relative path
291       * from that URL.  Note that the clip is not actually retrieved until the
292       * applet attempts to play it, so this method returns immediately. This
293       * calls <code>getAudioClip(new URL(url, name))</code>, but if building
294       * the new URL fails, this returns null.
295       *
296       * @param url the base URL of the audio clip
297       * @param name the name of the clip relative to the URL
298       * @return the retrieved audio clip, or null on failure
299       * @see #getAudioClip(URL)
300       */
301      public AudioClip getAudioClip(URL url, String name)
302      {
303        try
304          {
305            return getAudioClip(new URL(url, name));
306          }
307        catch (MalformedURLException e)
308          {
309            return null;
310          }
311      }
312    
313      /**
314       * Returns a descriptive string with applet defined information.  The
315       * implementation in this class returns <code>null</code>, so subclasses
316       * must override to return information.
317       *
318       * @return a string describing the author, version, and applet copyright
319       */
320      public String getAppletInfo()
321      {
322        return null;
323      }
324    
325      /**
326       * Returns the locale for this applet, if it has been set.  If no applet
327       * specific locale has been set, the default locale is returned.
328       *
329       * @return the locale for this applet
330       * @see Component#setLocale(Locale)
331       * @since 1.1
332       */
333      public Locale getLocale()
334      {
335        return super.getLocale();
336      }
337    
338      /**
339       * Returns a list of parameters this applet supports.  Each element of
340       * the outer array is an array of three strings with the name of the
341       * parameter, the data type or valid values, and a description.  This
342       * method is optional and the default implementation returns null.
343       *
344       * @return the list of parameters supported by this applet
345       */
346      public String[][] getParameterInfo()
347      {
348        return null;
349      }
350    
351      /**
352       * Loads and plays the audio clip pointed to by the specified URL. This does
353       * nothing if the URL does not point to a valid audio clip.
354       *
355       * @param url the URL of the audio clip
356       * @throws NullPointerException if url is null
357       * @see #getAudioClip(URL)
358       */
359      public void play(URL url)
360      {
361        AudioClip ac = getAudioClip(url);
362        try
363          {
364            ac.play();
365          }
366        catch (Exception ignored)
367          {
368          }
369      }
370    
371      /**
372       * Loads and plays the audio clip pointed to by the specified absolute URL,
373       * and relative path from that URL. This does nothing if the URL cannot be
374       * constructed, or if it does not point to a valid audio clip.
375       *
376       * @param url the base URL of the audio clip
377       * @param name the name of the audio clip relative to the URL
378       * @see #getAudioClip(URL, String)
379       * @see #play(URL)
380       */
381      public void play(URL url, String name)
382      {
383        try
384          {
385            getAudioClip(url, name).play();
386          }
387        catch (Exception ignored)
388          {
389          }
390      }
391    
392      /**
393       * This method is called when the applet is first loaded, before start().
394       * The default implementation does nothing; override to do any one-time
395       * initialization.
396       *
397       * @see #start()
398       * @see #stop()
399       * @see #destroy()
400       */
401      public void init()
402      {
403      }
404    
405      /**
406       * This method is called when the applet should start running.  This is
407       * normally each time a web page containing it is loaded.  The default
408       * implemention does nothing; override for your applet to be useful.
409       *
410       * @see #init()
411       * @see #stop()
412       * @see #destroy()
413       */
414      public void start()
415      {
416      }
417    
418      /**
419       * This method is called when the applet should stop running.  This is
420       * normally when the next web page is loaded.  The default implementation
421       * does nothing; override for your applet to stop using resources when
422       * it is no longer visible, but may be restarted soon.
423       *
424       * @see #init()
425       * @see #start()
426       * @see #destroy()
427       */
428      public void stop()
429      {
430      }
431    
432      /**
433       * This method is called when the applet is being unloaded.  The default
434       * implementation does nothing; override for your applet to clean up
435       * resources on exit.
436       *
437       * @see #init()
438       * @see #start()
439       * @see #stop()
440       */
441      public void destroy()
442      {
443      }
444    
445      /**
446       * Gets the AccessibleContext associated with this applet, creating one if
447       * necessary. This always returns an instance of {@link AccessibleApplet}.
448       *
449       * @return the accessibility context of this applet
450       * @since 1.3
451       */
452      public AccessibleContext getAccessibleContext()
453      {
454        if (accessibleContext == null)
455          accessibleContext = new AccessibleApplet();
456        return accessibleContext;
457      }
458    
459      /**
460       * Read an applet from an object stream. This checks for a headless
461       * environment, then does the normal read.
462       *
463       * @param s the stream to read from
464       * @throws ClassNotFoundException if a class is not found
465       * @throws IOException if deserialization fails
466       * @throws HeadlessException if this is a headless environment
467       * @see GraphicsEnvironment#isHeadless()
468       * @since 1.4
469       */
470      private void readObject(ObjectInputStream s)
471        throws ClassNotFoundException, IOException
472      {
473        if (GraphicsEnvironment.isHeadless())
474          throw new HeadlessException();
475        s.defaultReadObject();
476      }
477    
478      /**
479       * This class provides accessibility support for Applets, and is the
480       * runtime type returned by {@link #getAccessibleContext()}.
481       *
482       * @author Eric Blake (ebb9@email.byu.edu)
483       * @since 1.3
484       */
485      protected class AccessibleApplet extends AccessibleAWTPanel
486      {
487        /**
488         * Compatible with JDK 1.4+.
489         */
490        private static final long serialVersionUID = 8127374778187708896L;
491    
492        /**
493         * The default constructor.
494         */
495        protected AccessibleApplet()
496        {
497        }
498    
499        /**
500         * Get the role of this accessible object, a frame.
501         *
502         * @return the role of the object
503         * @see AccessibleRole#FRAME
504         */
505        public AccessibleRole getAccessibleRole()
506        {
507          return AccessibleRole.FRAME;
508        }
509    
510        /**
511         * Get the state set of this accessible object. In addition to the default
512         * states of a Component, the applet can also be active.
513         *
514         * @return the role of the object
515         * @see AccessibleState
516         */
517        public AccessibleStateSet getAccessibleStateSet()
518        {
519          AccessibleStateSet s = super.getAccessibleStateSet();
520          if (isActive())
521            s.add(AccessibleState.ACTIVE);
522          return s;
523        }
524      } // class AccessibleApplet
525    
526      private static class URLAudioClip implements AudioClip
527      {
528        // The URL we will try to play.
529        // This is null if we have already tried to create an
530        // audio input stream from this URL.
531        private URL url;
532    
533        // The real audio clip.  This is null before the URL is read,
534        // and might be null afterward if we were unable to read the URL
535        // for some reason.
536        private Clip clip;
537    
538        public URLAudioClip(URL url)
539        {
540          this.url = url;
541        }
542    
543        private synchronized Clip getClip()
544        {
545          if (url == null)
546            return clip;
547          try
548            {
549              clip = AudioSystem.getClip();
550              clip.open(AudioSystem.getAudioInputStream(url));
551            }
552          catch (LineUnavailableException _)
553            {
554              // Ignore.
555            }
556          catch (IOException _)
557            {
558              // Ignore.
559            }
560          catch (UnsupportedAudioFileException _)
561            {
562              // Ignore.
563            }
564          url = null;
565          return clip;
566        }
567    
568        public void loop()
569        {
570          Clip myclip = getClip();
571          if (myclip != null)
572            myclip.loop(Clip.LOOP_CONTINUOUSLY);
573        }
574    
575        public void play()
576        {
577          Clip myclip = getClip();
578          if (myclip != null)
579            myclip.start();
580        }
581    
582        public void stop()
583        {
584          Clip myclip = getClip();
585          if (myclip != null)
586            {
587              myclip.stop();
588              myclip.setFramePosition(0);
589            }
590        }
591      }
592    } // class Applet