iText - generating files on the fly without needin

问题:

I am trying to use iText for pdf file generation and I have a question regarding the generation. I would like to serve the PDF to the browser so that the browser displays it, without actually creating a file.

What would be the best approach to achieve this?

One limitation is that I would need to use it from a JSP page - something that would circumvent the "getOutputStream has already been called once" error is what I am looking for.

回答1:

I would like to serve the PDF to the browser so that the browser displays it, without actually creating a file.

Just pass responsegetOutputStream() instead of new FileOutputStream to PdfWriter.

PdfWriter pdfWriter = PdfWriter.getInstance(document, response.getOutputStream());
// ...

---

One limitation is that I would need to use it from a JSP page - something that would circumvent the "getOutputStream has already been called once" error is what I am looking for.

Just remove any whitespace outside <% %> in JSP, including newlines. They are implicitly sent to the response by the response writer.

I.e. do NOT

<% page import="foo" %>
<% page import="bar" %>

<%
   for (int i = 0; i < 1000; i++) {
       out.println("I should not use scriptlets.");
   }
%>

(newline here)

but more so

<% page import="foo" %><% page import="bar" %><%
   for (int i = 0; i < 1000; i++) {
       out.println("I should use servlets.");
   }
%>

Or better, don't put Java code in JSP files. JSP files are designed to present template text like HTML, not to do entirely different things. Do that in a normal Java class like a servlet.

回答2:

Write it to the servlet output stream, remembering to set the encoding to the correct value

回答3:

This http://onjava.com/onjava/2003/06/18/dynamic_files.html explains how to do it