Re: ASM-based class transformation affect class loading?

  Have you specified COMPUTE_FRAMES flag in the ClassWriter's accept()
method? If so, remove it, or overwrite its getCommonSuperClass(..)
method that won't load classes.

  regards,
  Eugene


On Tue, Aug 3, 2010 at 11:48 AM, Sai Zhang <[email protected]> wrote:
> Hi all:
>
> I met a strange problem when using ASM to transform my client code at load
> time (excluding all JDK code already).
>
> It seems that my transformer is highly likely to affect the class loading
> process. Please refer to the simple code below
> for illustration:
>
> Here is my simple ClassFileTransformer for load time class transformation,
> all transformation operations are
> in the treeAPITransform(byte[]) method. It is actually a fairly simple
> intra-method transformation based on the "tree api"
> of ASM (just adding tracing method at the begin/end of each method call)
>
>
> @Override
>     public byte[] transform(ClassLoader loader, String className,  Class<?>
> clazz, ProtectionDomain domain,   byte[] bytes) {
>          //code omitted here, for excluding all JDK classes
>
>            /*I print each loaded class for debugging */
> (1)   System.err.println("---- load class: " + className);
>
>         try {
> (2)          return this.treeAPITransform(bytes);   //my simple
> transformation implementation
>         } catch (Exception e) {
>             e.printStackTrace();
>             return null;
>         }
>     }
>
> The weird thing is that statement (1) does not print out some obviously
> loaded classes (which has definitely been initialized and executed).
> If I remove statement (2), or change that to "return null", every thing OK.
> all classes loaded are printed out at statement (1).
> I feel very confused on this point. I am wondering will ASM-based
> intra-method transformation affect the class loading? or
> did I instrument some extra classes by accident? or I should not use the
> tree api? or there is any tricks on this point?
> P.S. I use the ClassCheckerAdapter in ASM to check the validity of
> transformed bytecode after transformation. and no error messages
> are issued.
> thanks. Any comments are highly appreciated!!!
> -Sai
>
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