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   1  /* -*- Mode: Java; tab-width: 8; c-basic-offset: 4 -*-
   2  
   3      This program is free software; you can redistribute it and/or
   4      modify it under the terms of the GNU General Public License
   5      as published by the Free Software Foundation; either version 2
   6      of the License, or (at your option) any later version.
   7  
   8      This program is distributed in the hope that it will be useful,
   9      but WITHOUT ANY WARRANTY; without even the implied warranty of
  10      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11      GNU General Public License for more details.
  12  
  13      You should have received a copy of the GNU General Public License
  14      along with this program; if not, write to the Free Software
  15      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA. */
  16  
  17  /* more doc todo:
  18   *  threads
  19   *  gc
  20   *  
  21   *
  22   */
  23  
  24  package netscape.javascript;
  25  
  26  import java.applet.Applet;
  27  
  28  /**
  29   * JSObject allows Java to manipulate objects that are
  30   * defined in JavaScript.
  31   * Values passed from Java to JavaScript are converted as
  32   * follows:<ul>
  33   * <li>JSObject is converted to the original JavaScript object
  34   * <li>Any other Java object is converted to a JavaScript wrapper,
  35   *   which can be used to access methods and fields of the java object.
  36   *   Converting this wrapper to a string will call the toString method
  37   *   on the original object, converting to a number will call the
  38   *   doubleValue method if possible and fail otherwise.  Converting
  39   *   to a boolean will try to call the booleanValue method in the
  40   *   same way.
  41   * <li>Java arrays are wrapped with a JavaScript object that understands
  42   *   array.length and array[index]
  43   * <li>A Java boolean is converted to a JavaScript boolean
  44   * <li>Java byte, char, short, int, long, float, and double are converted
  45   *   to JavaScript numbers
  46   * </ul>
  47   * Values passed from JavaScript to Java are converted as follows:<ul>
  48   * <li>objects which are wrappers around java objects are unwrapped
  49   * <li>other objects are wrapped with a JSObject
  50   * <li>strings, numbers and booleans are converted to String, Double,
  51   *   and Boolean objects respectively
  52   * </ul>
  53   * This means that all JavaScript values show up as some kind
  54   * of java.lang.Object in Java.  In order to make much use of them,
  55   * you will have to cast them to the appropriate subclass of Object,
  56   * e.g. <code>(String) window.getMember("name");</code> or
  57   * <code>(JSObject) window.getMember("document");</code>.
  58   */
  59  public final class JSObject {
  60      /* the internal object data */
  61      private int                               internal;
  62      private long                              long_internal;
  63  
  64      /**
  65       * initialize
  66       */
  67      private static native void initClass();
  68      static {
  69          // On MRJ, this property won't exist, because the library is preloaded.
  70          String liveConnectLibrary = System.getProperty("netscape.jsj.dll", null);
  71          if (liveConnectLibrary != null) {
  72              System.loadLibrary(liveConnectLibrary);
  73              initClass();
  74          }
  75      }
  76  
  77      /**
  78       * it is illegal to construct a JSObject manually
  79       */
  80      private JSObject(int jsobj_addr) {
  81          internal = jsobj_addr;
  82      }
  83  
  84      private JSObject(long jsobj_addr) {
  85          long_internal = jsobj_addr;
  86      }
  87  
  88      /**
  89       * Retrieves a named member of a JavaScript object. 
  90       * Equivalent to "this.<i>name</i>" in JavaScript.
  91       */
  92      public native Object    getMember(String name);
  93  
  94      /**
  95       * Retrieves an indexed member of a JavaScript object.
  96       * Equivalent to "this[<i>index</i>]" in JavaScript.
  97       */
  98  //    public Object        getMember(int index) { return getSlot(index); }
  99      public native Object    getSlot(int index);
 100  
 101      /**
 102       * Sets a named member of a JavaScript object. 
 103       * Equivalent to "this.<i>name</i> = <i>value</i>" in JavaScript.
 104       */
 105      public native void         setMember(String name, Object value);
 106  
 107      /**
 108       * Sets an indexed member of a JavaScript object. 
 109       * Equivalent to "this[<i>index</i>] = <i>value</i>" in JavaScript.
 110       */
 111  //    public void         setMember(int index, Object value) {
 112  //        setSlot(index, value);
 113  //    }
 114      public native void         setSlot(int index, Object value);
 115  
 116      /**
 117       * Removes a named member of a JavaScript object.
 118       */
 119      public native void         removeMember(String name);
 120  
 121      /**
 122       * Calls a JavaScript method.
 123       * Equivalent to "this.<i>methodName</i>(<i>args</i>[0], <i>args</i>[1], ...)" in JavaScript.
 124       */
 125      public native Object    call(String methodName, Object args[]);
 126  
 127      /**
 128       * Evaluates a JavaScript expression. The expression is a string 
 129       * of JavaScript source code which will be evaluated in the context
 130       * given by "this".
 131       */
 132      public native Object    eval(String s);
 133  
 134      /**
 135       * Converts a JSObject to a String.
 136       */
 137      public native String        toString();
 138  
 139      // should use some sort of identifier rather than String
 140      // is "property" the right word?
 141    //    native String[]                         listProperties();
 142  
 143  
 144      /**
 145       * get a JSObject for the window containing the given applet
 146       */
 147      public static native JSObject    getWindow(Applet applet);
 148  
 149      /**
 150       * Finalization decrements the reference count on the corresponding
 151       * JavaScript object.
 152       */
 153      protected native void    finalize();
 154  
 155      /**
 156       * Override java.lang.Object.equals() because identity is not preserved
 157       * with instances of JSObject.
 158       */
 159      public native boolean equals(Object obj);
 160  }
 161  
 162