This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
BLOB implies bytes rather than characters. Since JSP is entirely oriented to making character pages, you should use a servlet to send byte data. In addition to the extension you would have to set content type and length headers. If you want Excel to read text, use comma delimited or tab delimited lines. Bill