php-java-bridge-users

[Php-java-bridge-users] LinkageException and remedy

[<php...@li...>]

Hi there!

Running (the otherwise excellent) php-java-bridge-4.1.8 I encountered a bug=
.

I had the following java-class structure

Class A
Class B extends A

>From php I referenced a remote EJB and called a method with the
following signature:

public A getA();

Where the method in fact returns an instance of  class B.

In php I then tried to figure out whether it was an instance of Class
A or B by using
java_instance_of:

$obj =3D $bean->getA();
$clazz =3D new JavaClass("org.test.B");
if ($clazz instanceof Java && java_instanceof($address, $clazz)){
  //...
} else {
 //...
}

However, this raised a LinkageException on the JVM, claiming that
Class B  already was loaded by the classloader.
If "$clazz =3D new JavaClass("org.test.B");" was performed before
"$bean->getA();" everything worked out fine, so I figured that
something was buggy in the dynamic classloading scheme.

I've attached a patch to the DynamicJavaBridgeClassLoader which
addresses this, by checking findLoadedClass(name) before
doLoadClass(name) but after verifying that it isn't in the cache.

/Sincerely
P-a B=E4ckstr=F6m
Sweden

Re: [Php-java-bridge-users] LinkageException and remedy

[<php...@li...>]

Hi,

this sounds like a bug to me.

Presumably java_instanceof() has never been tested with the DynamicClassLoader. Please see
ticket#1824173
(=>http://sourceforge.net/tracker/index.php?func=detail&aid=1824173&group_id=117793&atid=679233)
for details.

I haven't received your attachment, but I think we are able to reproduce this problem.


Regards,
Jost Boekemeier



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Re: [Php-java-bridge-users] LinkageException and remedy

[<php...@li...>]

php...@li... wrote:
> Hi,
>
> this sounds like a bug to me.
>
> Presumably java_instanceof() has never been tested with the DynamicClassLoader. Please see
> ticket#1824173
> (=>http://sourceforge.net/tracker/index.php?func=detail&aid=1824173&group_id=117793&atid=679233)
> for details.
>
> I haven't received your attachment, but I think we are able to reproduce this problem.
>
>
> Regards,
> Jost Boekemeier
>
>
>
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> php...@li...
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>
>   
Ok, I will monitor bug #1824173 then.

In the meantime, here's the small patch I wrote:

--- DynamicJavaBridgeClassLoader.java   2007-09-26 09:51:30.000000000 +0200
+++ 
php-java-bridge-4.1.8/server/php/java/bridge/DynamicJavaBridgeClassLoader.java  
2007-09-26 09:52:26.000000000 +0200
@@ -36,7 +36,6 @@
 import java.util.Set;
 import java.util.jar.JarFile;
 import java.util.jar.Manifest;
-
 /**
  * The bridge class loader which uses the DynamicClassLoader when 
possible.
  * @author jostb
@@ -217,12 +216,14 @@
                    if (c != null)
                    return (Class) c;
                    try {
-                   result = doLoadClass(name);
+                   result = findLoadedClass(name);
+                   if (result == null)
+                       result = doLoadClass(name);
                    cache.put(name, result);
                    return result;
                    } catch (ClassNotFoundException cnfe) {
                    cache.put(name, nf);
-                   }
+                   } 
                                }
                throw new ClassNotFoundException(name);
                }
~                 

Thanks a lot,
P-a Bäckström

Re: [Php-java-bridge-users] LinkageException and remedy

[<php...@li...>]

Hi,

I am sorry, but I could not reproduce this problem. Can you please attach a test case 
to the ticket #1824173
(http://sourceforge.net/tracker/index.php?func=detail&aid=1824173&group_id=117793&atid=679233)?


> However, this raised a LinkageException on the JVM, claiming that
> Class B  already was loaded by the classloader.

Yes, that's the expected behaviour when the same class is loaded twice by two different class
loaders.


> If "$clazz = new JavaClass("org.test.B");" was performed before
> "$bean->getA();" everything worked out fine

I don't think so. If you compare B@beanClassLoader with B@dynamicJavaBridgeClassLoader, you will
see that both classes are assignment incompatible.


> something was buggy in the dynamic classloading scheme.

There may be a bug in the dynamic class loader. But I fail to see it.


> I've attached a patch to the DynamicJavaBridgeClassLoader which
> addresses this, by checking findLoadedClass(name) before

The patch is incorrect. An attempt to load the same class twice must throw an exception. Otherwise
we will get ClassCastExceptions later on.

The problem, as I understand it, is, that you load the same class from two different locations.


Regards,
Jost Boekemeier



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