Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

11.2 The contentType Attribute

255

Figure 11 6 Result of Excel.jsp on system that has Excel installed.

A second way to format Excel content is to use a normal HTML table,

which recent versions of Excel can interpret properly as long as the page is

marked with the proper MIME type. This capability suggests a simple

method of returning either HTML or Excel content, depending on which

the user prefers: just use an HTML table and set the content type to

application/vnd.ms excel

 only if the user requests the results in Excel.

Unfortunately, this approach brings to light a small deficiency in the 

page

directive: attribute values cannot be computed at run time, nor can 

page

directives be conditionally inserted as can template text. So, the following

attempt results in Excel content regardless of the result of the 

checkUser 

Request

 method.

<% boolean usingExcel = checkUserRequest(request); %>

<% if (usingExcel) { %>

<%@ page contentType="application/vnd.ms excel" %>

<% } %>

Fortunately, there is a simple solution to the problem of conditionally set 

ting the content type: just use scriptlets and the normal servlet approach of

response.setContentType

, as in the following snippet:

<% 

String format = request.getParameter("format");

if ((format != null) && (format.equals("excel"))) { 

  response.setContentType("application/vnd.ms excel");

}  

%>

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.