001/* Applet.java -- Java base applet class 002 Copyright (C) 1999, 2002, 2004, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package java.applet; 040 041import java.awt.Component; 042import java.awt.Dimension; 043import java.awt.GraphicsEnvironment; 044import java.awt.HeadlessException; 045import java.awt.Image; 046import java.awt.Panel; 047import java.io.IOException; 048import java.io.ObjectInputStream; 049import java.net.MalformedURLException; 050import java.net.URL; 051import java.util.Locale; 052 053import javax.accessibility.AccessibleContext; 054import javax.accessibility.AccessibleRole; 055import javax.accessibility.AccessibleState; 056import javax.accessibility.AccessibleStateSet; 057import javax.sound.sampled.AudioSystem; 058import javax.sound.sampled.Clip; 059import javax.sound.sampled.LineUnavailableException; 060import 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 */ 076public 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><APPLET></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