libjava/java/beans/Beans.java

   1 /* java.beans.Beans
   2    Copyright (C) 1998, 1999 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.beans;
  40
  41 import java.io.*;
  42 import java.applet.*;
  43 import gnu.java.io.*;
  44
  45 /**
  46  * <code>Beans</code> provides some helper methods that allow the basic operations of Bean-ness.
  47  *
  48  * @author John Keiser
  49  * @since JDK1.1
  50  * @version 1.1.0, 29 Jul 1998
  51  *
  52  */
  53 public class Beans {
  54         static boolean designTime = false;
  55         static boolean guiAvailable = true;
  56
  57
  58         /**
  59          * Once again, we have a java.beans class with only
  60          * static methods that can be instantiated.  When
  61          * will the madness end? :)
  62          */
  63         public Beans() {
  64         }
  65
  66         /**
  67          * Allows you to instantiate a Bean.  This method takes
  68          * a ClassLoader from which to read the Bean and the
  69          * name of the Bean.<P>
  70          *
  71          * The Bean name should be a dotted name, like a class.
  72          * It can represent several things.  Beans will search
  73          * for the Bean using the name like this:<P>
  74          * <OL>
  75          * <LI>Searches for a serialized instance of the Bean
  76          * using getResource(), mangling the Bean name by
  77          * replacing the dots with slashes and appending .ser
  78          * (for example, gnu.beans.BlahDeBlah would cause
  79          * Beans to search for gnu/beans/BlahDeBlah.ser using
  80          * getResource()).</LI>
  81          * <LI>Searches for the Bean class using the beanName,
  82          * and then instantiates it with the no-arg constructor.
  83          * At that point, if it is an Applet, it provides it
  84          * with AppletContext and AppletStub, and then calls
  85          * init().</LI>
  86          * </OL>
  87          * @param cl the ClassLoader to use, or <CODE>null</CODE>
  88          *        to use the default ClassLoader.
  89          * @param beanName the name of the Bean.
  90          * @return the Bean.
  91          * @XXX
  92          */
  93         public static Object instantiate(ClassLoader cl, String beanName) throws IOException, ClassNotFoundException {
  94                 Object bean;
  95
  96                 InputStream serStream;
  97                 if(cl == null) {
  98                         serStream = ClassLoader.getSystemResourceAsStream(beanName.replace('.','/')+".ser");
  99                 } else {
 100                         serStream = cl.getResourceAsStream(beanName.replace('.','/')+".ser");
 101                 }
 102                 if(serStream != null) {
 103                         if(cl == null) {
 104                                 ObjectInputStream ois = new ObjectInputStream(serStream);
 105                                 bean = ois.readObject();
 106                         } else {
 107                                 ClassLoaderObjectInputStream ois = new ClassLoaderObjectInputStream(serStream, cl);
 108                                 bean = ois.readObject();
 109                         }
 110                 } else if(cl == null) {
 111                         Class beanClass = Class.forName(beanName);
 112                         try {
 113                                 bean = beanClass.newInstance();
 114                         } catch(IllegalAccessException E) {
 115                                 bean = null;
 116                         } catch(InstantiationException E) {
 117                                 bean = null;
 118                         }
 119                 } else {
 120                         Class beanClass = cl.loadClass(beanName);
 121                         try {
 122                                 bean = beanClass.newInstance();
 123                         } catch(IllegalAccessException E) {
 124                                 bean = null;
 125                         } catch(InstantiationException E) {
 126                                 bean = null;
 127                         }
 128                 }
 129
 130                 if(bean instanceof Applet) {
 131                         Applet a = (Applet)bean;
 132                         //a.setAppletContext(???);
 133                         //a.setStub(???);
 134                         if(serStream == null) {
 135                                 a.init();
 136                         }
 137                 }
 138
 139                 return bean;
 140         }
 141
 142         /**
 143          * Get the Bean as a different class type.
 144          * This should be used instead of casting to get a new
 145          * type view of a Bean, because in the future there may
 146          * be new types of Bean, even Beans spanning multiple
 147          * Objects.
 148          * @param bean the Bean to cast.
 149          * @param newClass the Class to cast it to.
 150          * @return the Bean as a new view, or if the operation
 151          *         could not be performed, the Bean itself.
 152          */
 153         public static Object getInstanceOf(Object bean, Class newClass) {
 154                 return bean;
 155         }
 156
 157         /**
 158          * Determine whether the Bean can be cast to a different
 159          * class type.
 160          * This should be used instead of instanceof to determine
 161          * a Bean's castability, because in the future there may
 162          * be new types of Bean, even Beans spanning multiple
 163          * Objects.
 164          * @param bean the Bean to cast.
 165          * @param newClass the Class to cast it to.
 166          * @return whether the Bean can be cast to the class type
 167          *         in question.
 168          */
 169         public static boolean isInstanceOf(Object bean, Class newBeanClass) {
 170                 return newBeanClass.isInstance(bean);
 171         }
 172
 173         /**
 174          * Find out whether the GUI is available to use.
 175          * Defaults to true.
 176          * @return whether the GUI is available to use.
 177          */
 178         public static boolean isGuiAvailable() {
 179                 return guiAvailable;
 180         }
 181
 182         /**
 183          * Find out whether it is design time.  Design time means
 184          * we are in a RAD tool.
 185          * Defaults to false.
 186          * @return whether it is design time.
 187          */
 188         public static boolean isDesignTime() {
 189                 return designTime;
 190         }
 191
 192         /**
 193          * Set whether the GUI is available to use.
 194          * @param guiAvailable whether the GUI is available to use.
 195          */
 196         public static void setGuiAvailable(boolean guiAvailable) throws SecurityException {
 197                 Beans.guiAvailable = guiAvailable;
 198         }
 199
 200         /**
 201          * Set whether it is design time.  Design time means we
 202          * are in a RAD tool.
 203          * @param designTime whether it is design time.
 204          */
 205         public static void setDesignTime(boolean designTime) throws SecurityException {
 206                 Beans.designTime = designTime;
 207         }
 208 }