001/* java.beans.Beans
002   Copyright (C) 1998, 1999, 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
038package java.beans;
039
040import gnu.java.beans.DummyAppletStub;
041import gnu.java.io.ClassLoaderObjectInputStream;
042
043import java.applet.Applet;
044import java.beans.beancontext.BeanContext;
045import java.io.IOException;
046import java.io.ObjectInputStream;
047import java.net.URL;
048
049/**
050 * <code>Beans</code> provides some helper methods that allow the basic
051 * operations of Bean-ness.
052 *
053 * @author John Keiser
054 * @author Robert Schuster
055 * 
056 * @since 1.1
057 * @status updated to 1.4
058 *
059 */
060public class Beans
061{
062  static boolean designTime = false;
063  static boolean guiAvailable = true;
064
065  /**
066   * Once again, we have a java.beans class with only
067   * static methods that can be instantiated.  When
068   * will the madness end? :)
069   */
070  public Beans()
071  {
072    // Does intentionally nothing here.
073  }
074
075   /** Creates a bean.
076    * <p>This is a convenience method that calls <code>instantiate(cl, beanName, null, null)</code>.</p>
077    * 
078    * @see instantiate(ClassLoader, String, BeanContext, AppletInitializer)
079    * @param cl ClassLoader to be used or <code>null</code> for the system classloader.
080    * @param beanName Name of a serialized bean or class name.
081    * @return A newly created bean.
082    * @throws IOException If access of an IO resource failed.
083    * @throws ClassNotFoundException If the class name is not known or does not lead to a proper bean class. 
084    */
085    public static Object instantiate(ClassLoader cl, String beanName)
086        throws IOException, ClassNotFoundException
087    {
088        return instantiate(cl, beanName, null, null);
089    }
090
091   /** Creates a bean.
092    * 
093    * <p>This is a convenience method that calls <code>instantiate(cl, beanName, beanContext, null)</code>.</p>
094    * 
095    * @see instantiate(ClassLoader, String, BeanContext, AppletInitializer)
096    * @param cl ClassLoader to be used or <code>null</code> for the system classloader.
097    * @param beanName Name of a serialized bean or class name.
098    * @param beanContext Context to which the newly created Bean should be added.
099    * @return A newly created bean.
100    * @throws IOException If access of an IO resource failed.
101    * @throws ClassNotFoundException If the class name is not known or does not lead to a proper bean class. 
102    */
103    public static Object instantiate(
104        ClassLoader cl,
105        String beanName,
106        BeanContext beanContext)
107        throws IOException, ClassNotFoundException
108    {
109        return instantiate(cl, beanName, beanContext, null);
110    }
111
112   /** Instantiates a bean according to Beans 1.0.
113    * 
114    * <p>In Beans 1.0 the instantiation scheme is as follows:</p>
115    * <p>The name should be dot-separated (e.g "place.for.beans.myBean") and indicate either a
116    * serialized object or a class name. In the first case all dots in the name are replaced with
117    * slashes ('/') and ".ser" is appended ("place.for.beans.myBean" becomes "place/for/beans/myBean.ser").
118    * The bean is then loaded as an application or system resource depending on whether a
119    * <code>ClassLoader</code> was provided.</p>
120    * 
121    * <p>If no such resource exists or if it contains no bean the name is interpreted as a class name of
122    * which an instance is then created.</p>
123    * 
124    * <p>If a <code>BeanContext</code> instance is available the created bean is added to it.</p>
125    * 
126    * <p>If the created Bean is an <code>Applet</code> or subclass and an <code>AppletInitializer</code>
127    * instance is available the applet is initialized and afterwards activated using the initializer. Additionally
128    * every instantiated <code>Applet</code> bean is initialized using the {@link Applet.init} method.
129    * Furthermore every applet gets a default <code>AppletStub</code>. The <code>Applet</code>'s
130    * document base is the location of the ".ser" file if it was deserialized or the location of its class
131    * file if it was instantiated.</p>
132    * 
133    * <p>A <code>ClassNotFoundException</code> is not only thrown when a class name was unknown
134    * but even when the class has public no-argument constructor
135    * (<code>IllegalAccessException</code> is wrapped) or an exception is thrown while
136    * invoking such a constructor (causing exception is wrapped).</p>
137    * 
138    * @param cl ClassLoader to be used or <code>null</code> for the system classloader.
139    * @param beanName Name of a serialized bean or class name.
140    * @param beanContext Context to which the newly created Bean should be added.
141    * @param initializer The AppletInitializer which is used for initializing <code>Applet</code> beans.
142    * @return A newly created bean.
143    * @throws IOException If access of an IO resource failed.
144    * @throws ClassNotFoundException If the class name is not known or does not lead to a proper bean class. 
145    */
146   public static Object instantiate(
147        ClassLoader cl,
148        String beanName,
149        BeanContext beanContext,
150        AppletInitializer initializer)
151        throws IOException, ClassNotFoundException
152   {
153        Object bean = null;
154        URL beanLocation = null;
155        URL classLocation = null;
156
157        // Converts bean name into a resource name (eg. "a.b.c" -> "a/b/c").  
158        String resourceName = beanName.replace('.', '/');
159
160        /* Tries to get an input stream of the Bean, reading it as a system resource
161         * if no ClassLoader is present or as an application resource if a classloader
162         * is given. 
163         */
164        beanLocation =
165            (cl == null)
166                ? ClassLoader.getSystemResource(resourceName + ".ser")
167                : cl.getResource(resourceName + ".ser");
168
169        // Reads the serialized Bean from the returned URL.
170        if (beanLocation != null)
171        {
172            // Deserializes the bean instance.
173            ObjectInputStream ois =
174                (cl == null)
175                    ? new ObjectInputStream(beanLocation.openStream())
176                    : new ClassLoaderObjectInputStream(
177                        beanLocation.openStream(),
178                        cl);
179
180            bean = ois.readObject();
181
182            /* Implementation note: The result of ObjectInputStream.readObject()
183            * may have been null at this point (its a valid value to deserialize)
184            * and we explicitly want to try instantiation in such a case
185            * (this is important for compatibility).
186            */
187        }
188
189        // Instantiates the Bean using reflective instantiation if it has not been created yet.
190        if (bean == null)
191        {
192            // Makes sure that the deserialization was NOT done.
193            beanLocation = null;
194
195            Class beanClass;
196            if (cl == null)
197            {
198                beanClass = Class.forName(beanName);
199                classLocation =
200                    ClassLoader.getSystemResource(resourceName + ".class");
201            }
202            else
203            {
204                beanClass = cl.loadClass(beanName);
205                classLocation = cl.getResource(resourceName + ".class");
206            }
207
208            // Instantiates and optionally registers the new bean.
209            try
210            {
211                bean = beanClass.newInstance();
212            }
213            catch(Exception e) {
214                /* Wraps all kinds of Exceptions in a ClassNotFoundException (this behavior
215                 * matches with official >= 1.5, this was different for <=1.4)
216                 */
217                throw new ClassNotFoundException(null, e);
218            }
219        }
220
221        /* Applet beans are treated in the following way:
222         * - all AppletS get a default AppletStub
223         * - all AppletS are initialized using the AppletInitializer instance (if it is available)
224         * - as every other Bean Applets are added to a BeanContext if one is available
225         * - each instantiated Applet is initialized using Applet.init() (this is not done for deserialized ones)
226         * - finally AppletS get activated using the AppletInitializerS activate-Method
227         * 
228         * The order of operations is important for compatibility.    
229         */
230        Applet applet = null;
231        if (bean instanceof Applet)
232        {
233            // Makes a second instanceof call unneccessary (instanceof is expensive).
234            applet = (Applet) bean;
235
236            /* The AppletStub's code and document base is set as follows:
237             * The code base is always the URL from where the class data originated
238             * (without the package name).
239             * If the Applet was deserialized the document base is the location of
240             * the serialized instance (usually the ".ser" file) otherwise its the URL
241             * from where the class data originated (usually the absolute directory
242             * location of the ".class" file).
243             */
244            applet.setStub(
245                new DummyAppletStub(
246                    applet
247                        .getClass()
248                        .getProtectionDomain()
249                        .getCodeSource()
250                        .getLocation(),
251                    (beanLocation == null) ? classLocation : beanLocation));
252
253            // Runs the Applet's initialization using an AppletInitializer.
254            if (initializer != null)
255            {
256                initializer.initialize(applet, beanContext);
257            }
258        }
259
260        // Adds the new bean to its BeanContext.
261        if (beanContext != null)
262        {
263            beanContext.add(bean);
264        }
265
266        if (applet != null)
267        {
268
269            // Initializes an instantiated (not deserialized) Applet using its own method.
270            if (beanLocation == null)
271            {
272                applet.init();
273            }
274
275            // Runs the Applet's activation using an AppletInitializer.
276            if (initializer != null)
277            {
278                initializer.activate(applet);
279            }
280        }
281
282        return bean;
283   }
284
285   /**
286    * Returns the Bean as a different class type.
287    * This should be used instead of casting to get a new
288    * type view of a Bean, because in the future there may
289    * be new types of Bean, even Beans spanning multiple
290    * Objects.
291    *
292    * @param bean the Bean to cast.
293    * @param newClass the Class to cast it to.
294    *
295    * @return the Bean as a new view, or if the operation
296    *         could not be performed, the Bean itself.
297    */
298   public static Object getInstanceOf(Object bean, Class<?> newClass)
299   {
300        return bean;
301   }
302
303   /**
304    * Determines whether the Bean can be cast to a different
305    * class type.
306    * This should be used instead of instanceof to determine
307    * a Bean's castability, because in the future there may
308    * be new types of Bean, even Beans spanning multiple
309    * Objects.
310    *
311    * @param bean the Bean to cast.
312    * @param newBeanClass the Class to cast it to.
313    *
314    * @return whether the Bean can be cast to the class type
315    *         in question.
316    */
317   public static boolean isInstanceOf(Object bean, Class<?> newBeanClass)
318   {
319       return newBeanClass.isInstance(bean);
320   }
321
322   /**
323    * Returns whether the GUI is available to use.
324    * <p>Defaults to true.</p>
325    *
326    * @return whether the GUI is available to use.
327    */
328   public static boolean isGuiAvailable()
329   {
330       return guiAvailable;
331   }
332
333   /**
334    * Returns whether it is design time.  Design time means
335    * we are in a RAD tool.
336    * <p>Defaults to false.</p>
337    *
338    * @return whether it is design time.
339    */
340   public static boolean isDesignTime()
341   {
342       return designTime;
343   }
344
345   /**
346    * Sets whether the GUI is available to use.
347    * 
348    * @param guiAvailable whether the GUI is available to use.
349    */
350   public static void setGuiAvailable(boolean guiAvailable)
351       throws SecurityException
352   {
353        Beans.guiAvailable = guiAvailable;
354   }
355
356   /**
357    * Sets whether it is design time.  Design time means we
358    * are in a RAD tool.
359    *
360    * @param designTime whether it is design time.
361    */
362   public static void setDesignTime(boolean designTime)
363       throws SecurityException
364   {
365       Beans.designTime = designTime;
366   }
367
368}