final Bytecode code = new Bytecode( constPool, 2, 1 );
// aload_0 // load this
code.addAload( 0 );
// getfield // get field "$JAVASSIST_CALLBACK" defined already
code.addOpcode( Opcode.GETFIELD );
final int fieldIndex = constPool.addFieldrefInfo( thisClassInfo, HANDLER_FIELD_NAME, HANDLER_FIELD_DESCRIPTOR );
code.addIndex( fieldIndex );
// areturn // return the value of the field
code.addOpcode( Opcode.ARETURN );
getterMethodInfo.setCodeAttribute( code.toCodeAttribute() );
getterMethodInfo.setAccessFlags( AccessFlag.PUBLIC );