Reading xls file in gwt - gwt

Question

I am looking to read xls file using the gwt RPC and when I am using the code which excecuted fine in normal file it is unable to load the file and giving me null pointer exception.
Following is the code
{
{
import com.arosys.readExcel.ReadXLSX;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;
import org.Preview.client.GWTReadXL;
import java.io.InputStream;
import com.arosys.customexception.FileNotFoundException;
import com.arosys.logger.LoggerFactory;
import java.util.Iterator;
import org.apache.log4j.Logger;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
/**
*
* #author Amandeep
*/
public class GWTReadXLImpl extends RemoteServiceServlet implements GWTReadXL
{
private String fileName;
private String[] Header=null;
private String[] RowData=null;
private int sheetindex;
private String sheetname;
private XSSFWorkbook workbook;
private XSSFSheet sheet;
private static Logger logger=null;
public void loadXlsxFile() throws Exception
{
logger.info("inside loadxlsxfile:::"+fileName);
InputStream resourceAsStream =ClassLoader.getSystemClassLoader().getSystemResourceAsStream("c:\\test2.xlsx");
logger.info("resourceAsStream-"+resourceAsStream);
if(resourceAsStream==null)
throw new FileNotFoundException("unable to locate give file");
else
{
try
{
workbook = new XSSFWorkbook(resourceAsStream);
sheet = workbook.getSheetAt(sheetindex);
}
catch (Exception ex)
{
logger.error(ex.getMessage());
}
}
}// end loadxlsxFile
public String getNumberOfColumns() throws Exception
{
int NO_OF_Column=0; XSSFCell cell = null;
loadXlsxFile();
Iterator rowIter = sheet.rowIterator();
XSSFRow firstRow = (XSSFRow) rowIter.next();
Iterator cellIter = firstRow.cellIterator();
while(cellIter.hasNext())
{
cell = (XSSFCell) cellIter.next();
NO_OF_Column++;
}
return NO_OF_Column+"";
}
}
}
I am calling it in client program by this code:
final AsyncCallback<String> callback1 = new AsyncCallback<String>() {
public void onSuccess(String result) {
RootPanel.get().add(new Label("In success"));
if(result==null)
{
RootPanel.get().add(new Label("result is null"));
}
RootPanel.get().add(new Label("result is"+result));
}
public void onFailure(Throwable caught) {
RootPanel.get().add(new Label("In Failure"+caught));
}
};
try{
getService().getNumberOfColumns(callback1);
}catch(Exception e){}
}
Pls tell me how can I resolve this issue as the code runs fine when run through the normal java file.

Answer 1

Why are using using the system classloader, rather than the normal one?
But, If you still want to use then look at this..
As you are using like a web application. In that case, you need to use the ClassLoader which is obtained as follows:
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
This one has access to the all classpath paths tied to the webapplication in question and you're not anymore dependent on which parent classloader (a webapp has more than one!) has loaded your class.
Then, on this classloader, you need to just call getResourceAsStream() to get a classpath resource as stream, not the getSystemResourceAsStream() which is dependent on how the webapplication is started. You don't want to be dependent on that as well since you have no control over it at external hosting:
InputStream input = classLoader.getResourceAsStream("filename.extension");
The location of file should in your CLASSPATH.