java.lang.NoClassDefFoundError coming while reading .xlsx file in java project

[shubham pateriya]

Hi,
I am using following code in my project to process .xlsx file

                OPCPackage pkg = OPCPackage.open(fileName);
 	XSSFReader r = new XSSFReader( pkg );
	SharedStringsTable sst = r.getSharedStringsTable();
                XMLReader parser = fetchSheetParser(sst);
                     

I have added follwoing jar files in my classpath:
(1) poi-3.6-20091214
(2) dom4j-1.6.1
(3) ooxml-schemas-1.0
(4) xerces-2.2.1
(5) poi-ooxml-3.6-20100309
(6) xmlbeans-2.3.0
(7) log4j-1.2.9

still I am getting "java.lang.ClassCastException: java.lang.NoClassDefFoundError cannot be cast to java.lang.Exception."
I have noticed that when control is coming on

OPCPackage pkg = OPCPackage.open(fileName);

line, it throws exception, and come out of try- catch block.
Please help.