Question

How to make an excel file (and txt file) filled with data from a table on the html page in a servlet and send it to a browser?

Answer 1

Firstly you need to generate the actual content (e.g. an Excel file). Apache POI can generate Excel spreadsheets easily. Alternatively you can simply generate a .csv file.

Secondly you need to return it with the correct content type. See this Javaworld tip for more info. Briefly, you set the content type on the response thus.

// MIME type for Excel
res.setContentType( "application/vnd.ms-excel" ); 

will set an Excel MIME type. text/csv would work if you generate a CSV file.

You may also want to set the filename for downloading.

res.setHeader("Content-disposition",
                  "attachment; filename=Example.xls" );

uses the content-disposition header to achieve this.