Question

I need to provide a feature where user can download reports in excel/csv format in my web application. Once i made a module in web application which creates excel and then read it and sent to browser. It was working correctly. This time i don’t want to generate excel file, as i don’t have that level of control over file systems. I guess one way is to generate appropriate code in StringBuffer and set correct contenttype(I am not sure about this approach). Other team also has this feature but they are struggling when data is very large. What is the best way to provide this feature considering size of data could be very huge. Is it possible to send data in chunk without client noticing(except delay in downloading).
One issue i forgot to add is when there is very large data, it also creates problem in server side (cpu utilization and memory consumption). Is it possible that i read fixed amount of records like 500, send it to client, then read another 500 till completed.

Answer 1

You can also generate HTML instead of CSV and still set the content type to Excel. This is nice for colouring and styled text.

You can also use gzip compression when the client accepts that compression. Normally there are standard means, like a servlet filter.

Never a StringBuffer or the better StringBuilder. Better streaming it out. If you do not (cannot) call setContentength, the output goes chunked (without predictive progress).