gecko-dev/js/rhino
norris%netscape.com 600d365e30 Patch from Matthias Radestock <rade@logee.com>:
Subject:
             JavaAdapter return type conversion
        Date:
             Wed, 19 Apr 2000 12:12:47 +0100
       From:
             Matthias Radestock <rade@logee.com>
 Organization:
             Logee
         To:
             norris@netscape.com
         CC:
             mccabe@netscape.com, beard@netscape.com, rogerl@netscape.com




Dear Rhino team,

When returning an array from a scripted Java object (i.e. a JS object
that implements a Java interface), no type conversion is performed, ie.
a NativeArray is returned instead of a Java array. Example:

Java:
interface Foo {
        public String[] boo();
        }

JS:
FooI = {
        boo: function() { return ["Boo"];}
        }
myFoo = new Packages.Foo(FooI);
myFoo.boo(); //==> breaks with a ClassCastException


Looking at the JavaAdapter code, there is no code for array conversion.
This is particularly bad because precisely such a conversion *does*
happen when calling a Java method from JS. So we end up with a
discrepancy.

See attachment for a patch to fix this and little test program. The
patch works by calling the coerceType function on NativeJavaObject,
which is the function responsible for doing the conversion when calling
from JS to Java. I've simplified the code so that this function gets
called for all non-primitive return type, not just arrays. There are
probably more efficient solutions but I'm not a Java bytecode hacker.


Matthias
PS: I didn't open a bug for this because I wasn't sure whether you guys
would agree that this is indeed a problem ;)





public interface JSReturnTest {

  public boolean returnBoolean();
  public char returnChar();
  public int returnInt();
  public String returnString();
  public org.mozilla.javascript.Scriptable returnScriptable();
  public Object returnObject();
  public boolean[] returnBooleanA();
  public char[] returnCharA();
  public int[] returnIntA();
  public String[] returnStringA();
  public org.mozilla.javascript.Scriptable[] returnScriptableA();
  public Object[] returnObjectA();
  public Object[][] returnObjectAA();
}




Index: JavaAdapter.java
===================================================================
RCS file: /cvsroot/mozilla/js/rhino/org/mozilla/javascript/JavaAdapter.java,v
retrieving revision 1.21
diff -r1.21 JavaAdapter.java
54c54,59
<
---
>
>     public static Object convertResult(Object result, String classname)
>     throws ClassNotFoundException {
>         return NativeJavaObject.coerceType(Class.forName(classname),
>                                            result);
>     }
467,474c472,474
<         } else  if (retType.equals(String.class)) {
<             cfw.add(ByteCode.INVOKESTATIC,
<                     "org/mozilla/javascript/Context",
<                     "toString", "(Ljava/lang/Object;)",
<                     "Ljava/lang/String;");
<             cfw.add(ByteCode.ARETURN);
<         } else if (retType.equals(Scriptable.class)) {
<             cfw.add(ByteCode.ALOAD_0);  // load 'this' to find scope from
---
>         } else {
>             String retTypeStr = retType.getName();
>             cfw.addLoadConstant(retTypeStr);
476,477c476,477
<                     "org/mozilla/javascript/Context",
<                     "toObject",
---
>                     "org/mozilla/javascript/JavaAdapter",
>                     "convertResult",
479,500c479,480
<                      "Lorg/mozilla/javascript/Scriptable;)",
<                     "Lorg/mozilla/javascript/Scriptable;");
<             cfw.add(ByteCode.ARETURN);
<         } else {
<             // If it is a wrapped type, cast to Wrapper and call unwrap()
<             cfw.add(ByteCode.DUP);
<             cfw.add(ByteCode.INSTANCEOF, "org/mozilla/javascript/Wrapper");
<             // skip 3 for IFEQ, 3 for CHECKCAST, and 5 for INVOKEINTERFACE
<             cfw.add(ByteCode.IFEQ, 11);
<             cfw.add(ByteCode.CHECKCAST, "org/mozilla/javascript/Wrapper");
<             cfw.add(ByteCode.INVOKEINTERFACE,
<                     "org/mozilla/javascript/Wrapper",
<                     "unwrap", "()", "Ljava/lang/Object;");
<
<             // If Undefined, return null
<             cfw.add(ByteCode.DUP);
<             cfw.add(ByteCode.INSTANCEOF, "org/mozilla/javascript/Undefined");
<             // skip 3 for IFEQ, 1 for ACONST_NULL, 1 for ARETURN
<             cfw.add(ByteCode.IFEQ, 5);
<             cfw.add(ByteCode.ACONST_NULL);
<             cfw.add(ByteCode.ARETURN);
<
---
>                     "Ljava/lang/String;)",
>                     "Ljava/lang/Object;");
502,503c482
<             String retTypeStr = retType.getName().replace('.', '/');
<             cfw.add(ByteCode.CHECKCAST, retTypeStr);
---
>             cfw.add(ByteCode.CHECKCAST, retTypeStr.replace('.', '/'));



   testpatch.js

               Name:
                     testpatch.js
                Type:
                     JavaScript Program (application/x-javascript)
             Encoding:
                     7bit
2000-04-24 19:36:51 +00:00
..
examples
macbuild
org/mozilla Patch from Matthias Radestock <rade@logee.com>: 2000-04-24 19:36:51 +00:00
src/org/mozilla Patch from Matthias Radestock <rade@logee.com>: 2000-04-24 19:36:51 +00:00
toolsrc/org/mozilla/javascript/tools
Makefile
manifest
README.html

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<h1>
<span CLASS=LXRSHORTDESC>
Rhino: JavaScript in Java<p>
</span>
</h1>
<span CLASS=LXRLONGDESC>
Rhino is an implementation of JavaScript in Java. Documentation can be found 
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