VerifyError when instanciating a generated class (Bad type i

[kromate]

Dear all,

I'm using javassist to generate access class for reflection, following this tutorial:
http://www.ibm.com/developerworks/java/library/j-dyn0610/index.html?S_TACT=105AGX02&S_CMP=EDU

Everything works fine with my version, but it is not working with field without getter/setter. I need my generated access class to be able to access field directly in some case.

So I wrote the following piece of code:

....
protected static byte[] createAccess(final Class targetJavaClass, final String field, final String generatedClassName)
 throws Exception {

//... code to get read/write method

 String targetName = targetJavaClass.getName();
 ClassPool pool = ClassPool.getDefault();
 CtClass accessClass = pool.makeClass(generatedClassName);
 CtClass targetClass = pool.get(targetName);
 final CtClass ctFieldClass = pool.get("java.lang.Object");
 final CtClass[] ctFieldClassParam = new CtClass[]{ctFieldClass};
 CtMethod meth;

 // add target object field to class
 accessClass.addField(new CtField(targetClass, "target", accessClass));

 // add public default constructor method to class
 CtConstructor cons = new CtConstructor(CT_NO_ARGS, accessClass);
 cons.setBody(";");
 accessClass.addConstructor(cons);

 // add public <code>setTarget</code> method
 meth = new CtMethod(CtClass.voidType, "setTarget", ctFieldClassParam, accessClass);
 meth.setBody("target = (" + targetJavaClass.getName() + ") $1;");
 accessClass.addMethod(meth);


 String src;

 // add public <code>setValue</code> method
 meth = new CtMethod(CtClass.voidType, "setValue", ctFieldClassParam, accessClass);
 final Class<?> fieldType = writer.getParameterTypes()[0];
 String cast$1 = "(" + fieldType.getName() + ") $1";
 if(directWriteField) src = "target." + field + " = " + " $1;";
 else src = "target." + writer.getName() + "(" + cast$1 + ");";
 meth.setBody(src);
 accessClass.addMethod(meth);

 // add public <code>getValue</code> method
 meth = new CtMethod(ctFieldClass, "getValue", CT_NO_ARGS, accessClass);
 if(directReadField) src = field;
 else src = reader.getName() + "()";
 meth.setBody("return (java.lang.Object) target." + src + ";");
 accessClass.addMethod(meth);

 // return binary representation of completed class
 accessClass.addInterface(pool.get(IAccess.class.getName()));
 accessClass.writeFile();
 return accessClass.toBytecode();
 }
...

Execution of this code throws an exception after class generation, when calling newInstance on it:

java.lang.VerifyError: (class: Accessor$com/bnpparibas/eqd/fish/fwk/introspection/TestCachedIntrospectionInfo$SampleBean_secret, method: setValue signature: (Ljava/lang/Object;)V) Bad type in
putfield/putstatic
at java.lang.Class.getDeclaredConstructors0(Native Method)
 at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
 at java.lang.Class.getConstructor0(Class.java:2671)
 at java.lang.Class.newInstance0(Class.java:321)
 at java.lang.Class.newInstance(Class.java:303)

The part of the code responsible of this is the following part of code:

f(directWriteField) src = "target." + field + " = " + " $1;";

If I remove this line, there are no error.

Here is the decompiled code of the faulty generated class:

package Accessor$com.bnpparibas.eqd.fish.fwk.introspection;

import com.bnpparibas.eqd.fish.fwk.introspection.IAccess;
import com.bnpparibas.eqd.fish.fwk.introspection.SampleBean;

public class SampleBean_directAccessField
 implements IAccess {

 SampleBean target = null;

 public SampleBean_directAccessField() {
 }

 public void setTarget(Object obj) {
 target = (SampleBean)obj;
 }

 public void setValue(Object obj) {
 target.directAccessField = ((java.util.Date) (obj));
 }

 public Object getValue() {
 return (Object)target.directAccessField;
 }
}

And the directAccesField of the target object is a java.util.Date.

I've spend to much time on this problem and I can't figure what the problem is.

Thanks for any help you can provide.

Regards.
K.

[jaikiran]

public class SampleBean_directAccessField
implements IAccess {

SampleBean target = null;


public void setValue(Object obj) {
target.directAccessField = ((java.util.Date) (obj));
}

Is the "directAccessField" in SampleBean a public field? If it's not, then it won't be accessible.

[kromate]

Yes this is a public field.

In this case the error will much be something like an IllegalAccessException.

It's like there is a type problem.

The strange thing is that this line is not working:

if(directWriteField) src = "target." + field + " = " + " $1;";

but this one is:

if(directWriteField) src = "target." + field + " = new java.util.Date();";

[kromate]

The last line of my previous post is not easy to read. It is:
if(directWriteField) src = "target." + field + " = new java.util.Date();";

[kromate]

By the way I re-post the error I get with this code. The one I've posted is was not matching.

Caused by: java.lang.VerifyError: (class: Accessor$com/bnpparibas/eqd/fish/fwk/introspection/SampleBean_directAccessField, method: setValue signature: (Ljava/lang/Object;)V) Bad type in putfield/putstatic
 at java.lang.Class.getDeclaredConstructors0(Native Method)
 at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
 at java.lang.Class.getConstructor0(Class.java:2671)
 at java.lang.Class.newInstance0(Class.java:321)
 at java.lang.Class.newInstance(Class.java:303)

(out of topic) his there an edit post tool ? I've looked for one, but I did not see any.

Thanks.

[jaikiran]

Looking at this code:

String cast$1 = "(" + fieldType.getName() + ") $1";
if(directWriteField) src = "target." + field + " = " + " $1;";

I think you have a typo. You should be having this:

String cast$1 = "(" + fieldType.getName() + ") $1";
 if(directWriteField) src = "target." + field + " = " + cast$1 + ";";

(out of topic) his there an edit post tool ?

No, there's no edit option.