001    /* java.beans.Beans
002       Copyright (C) 1998, 1999, 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    package java.beans;
039    
040    import gnu.java.beans.DummyAppletStub;
041    import gnu.java.io.ClassLoaderObjectInputStream;
042    
043    import java.applet.Applet;
044    import java.beans.beancontext.BeanContext;
045    import java.io.IOException;
046    import java.io.ObjectInputStream;
047    import 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     */
060    public 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    }