Output a binary stream from a JSPTag(s): Servlet/JSP


You can't.

From JSP, only character stream should be used.

JSP pages were designed for *text* output. The "out" object is a Writer, which means it will play games with text encoding.

For binary output, like PDF or dynamically generated GIF, it's a better idea to use a servlet.

Having said that, since a JSP will be converted to a servlet, it's possible to modifed the output stream.

You must be careful to format your JSP to emit no whitespace

[image.jsp]

<%@ page import="java.io.*" %>
<%@ page import="java.net.*" %>
<%@page contentType="image/gif" %><%
    OutputStream o = response.getOutputStream();
    InputStream is = 
      new URL("http://myserver/myimage.gif").getInputStream();
    byte[] buf = new byte[32 * 1024]; // 32k buffer
    int nRead = 0;
    while( (nRead=is.read(buf)) != -1 ) {
        o.write(buf, 0, nRead);
    }
    o.flush();
    o.close();// *important* to ensure no more jsp output
    return; 
%>
Thanks to Benjamin Grant for the bug fix.

There is a trimWhiteSpaces directive that should help to remove the whitespaces form the generated JSP.

In your JSP code :

<%@ page trimDirectiveWhitespaces="true" %>
Or in the jsp-config section your web.xml
<jsp-config>
  <jsp-property-group>
    <url-pattern>*.jsp</url-pattern>
    <trim-directive-whitespaces>true</trim-directive-whitespaces>
  </jsp-property-group>
</jsp-config>
If you really have a required space in the generated JSP then you need use the HTML non-breaking space entity : &nbsp; .
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