Array Class Literals

[hlovatt]

Hi,

The following code fails in the Javassist compiler:

if ( $3 instanceof Object[].class )
 return $3.length;

Instead I have to use:

Class array = java.lang.reflect.Array.newInstance( Object.class, 0 ).getClass();
if ( array.isInstance( $3 ) )
 return $3.length;

Are there plans to add array class literals?

Is there a better work around?

Keep up the good work - Howard.

[hlovatt]

Ignore - I forgot to watch the topic :)

[chiba]

Let me make sure.
Javassist 3 can compile Object[].class.

Chiba

[hlovatt]

3 couldn't when I tried the above example.

Howard.

[chiba]

Really?
Can you post a complete test case?
Thanks!

[hlovatt]

First two appologies: I don't seem to be able to watch this thread so I missed your post and secondly my test class is a little long :( . Take a look at lines 75 to 90 which demonstrate the problem I am having with array class literals and also with testing for null on primitive arrays (see seperate post to this forum for null problems).

package examples.javassisttests.poolget;

import javassist.*;
import pec.compile.*;
import java.io.*;
import java.lang.reflect.*;

public class Test {
 static class Y {}
 static class X extends Y {}
 public static void main( final String[] notUsed ) throws Exception {
 // Test of assignment compatability
 final X[] xs = new X[ 1 ];
 final Y[] ys = xs;
 ys[ 0 ] = new X(); // OK
 // ys[ 0 ] = new Y(); // ArrayStoreException
 final ClassPool pool = ClassPool.getDefault();
 final CtClass intClass = pool.get( "int" );
 final CtClass longClass = pool.get( "long" );
 System.out.println( "Class: " + long.class.isAssignableFrom( int.class ) );
 System.out.println( "CtClass: " + longClass.subtypeOf( intClass ) );

 // get classes
 System.out.println( "int = " + intClass );
 final CtClass intArrayClass = pool.get( "int[]" );
 System.out.println( "int[] = " + intArrayClass );
 final CtClass objectArrayClass = pool.get( "java.lang.Object[]" );
 System.out.println( "Object[] = " + objectArrayClass );

 // class definition (AbstractTest)
 final CtClass clazz = pool.makeClass( "examples.javassisttests.poolget.AbstractTest" );
 clazz.setModifiers( javassist.Modifier.ABSTRACT );
 clazz.setModifiers( javassist.Modifier.PUBLIC );

 // protected constructor definition
 final CtConstructor constructor = CtNewConstructor.defaultConstructor(
 clazz );
 constructor.setModifiers( javassist.Modifier.PROTECTED );
 clazz.addConstructor( constructor );

 // abstract method definition
 final CtClass[] arguments = new CtClass[] { intClass, intArrayClass, objectArrayClass };
 final CtMethod method = CtNewMethod.abstractMethod(
 intClass,
 "f",
 arguments,
 null,
 clazz );
 clazz.addMethod( method );

 // write the abstract class
 clazz.writeFile( "C:\\Personal\\Java" );

 // print the abstract class
 final Class classOfClazz = Class.forName( "examples.javassisttests.poolget.AbstractTest" );
 System.out.println();
 Utilities.printSignature( classOfClazz, null );

 // class definition (DerivedTest)
 final CtClass derivedClass = pool.makeClass(
 "examples.javassisttests.poolget.DerivedTest", clazz );
 derivedClass.setModifiers( javassist.Modifier.PUBLIC );

 // public constructor definition
 final CtConstructor derivedConstructor = CtNewConstructor.defaultConstructor(
 derivedClass );
 derivedClass.addConstructor( derivedConstructor );

 // method definition
 final CtMethod derivedMethod = CtNewMethod.make(
 intClass,
 "f",
 arguments,
 null,
 /*"{\n" +
 " if ( $2 != null )\n" +
 " return $2.length;\n" +
 " if ( $3 instanceof Object[].class )\n" +
 " return $3.length;\n" +
 " return $1;\n" +
 "}",*/
 "{\n" +
 " if ( System.identityHashCode( $2 ) != 0 )\n" +
 " return $2.length;\n" +
 " Class array = java.lang.reflect.Array.newInstance( Object.class, 0 ).getClass();\n" +
 " if ( array.isInstance( $3 ) )\n" +
 " return $3.length;\n" +
 " return $1;\n" +
 "}",
 derivedClass );
 derivedClass.addMethod( derivedMethod );

 // write the derived class
 derivedClass.writeFile( "C:\\Personal\\Java" );

 // print derived class
 final Class classOfDerivedClazz = Class.forName( "examples.javassisttests.poolget.DerivedTest" );
 System.out.println();
 Utilities.printSignature( classOfDerivedClazz, null );

 // Test DerivedTest
 System.out.println();
 final Method methodF = classOfDerivedClazz.getMethod( "f", new Class[] { int.class, int[].class, Object[].class } );
 final Object dt = classOfDerivedClazz.newInstance();
 int value;
 value = ((Integer) methodF.invoke( dt, new Object[] { new Integer( 1 ), null, null } )).intValue();
 System.out.println( "f() = " + value );
 value = ((Integer) methodF.invoke( dt, new Object[] { new Integer( 1 ), new int[ 2 ], null } )).intValue();
 System.out.println( "f() = " + value );
 value = ((Integer) methodF.invoke( dt, new Object[] { new Integer( 1 ), null, new Object[ 3 ] } )).intValue();
 System.out.println( "f() = " + value );
 }
}