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2. Excel Data Population using Java

4. Code for transfering data from JSP to Excel Sheet

Do you need to preserve whatever formatting (fonts, bold, alignment, etc.) is used as well? If so, a library like POI is indeed your only choice. If it's only the actual values you're interested in, you might as well just create a CSV file and stream that to the client (using one of the many available Java CSV libraries).

6. Jsp and data in Excel