Servlet error from ImageIO

Question

Does anyone know why the following call to createImageOutputStream works fine in a method called from a stand-alone main(), but generates a servlet error when the same method is called from a jsp using the same parameters?
try {
File f = new File(outputFile);
if (f != null) {
ImageOutputStream ios = ImageIO.createImageOutputStream(f);
No exception is thrown, just a stack dump to stdout.
Below is a partial stack trace.
Servlet Error: javax/imageio/ImageIO: java.lang.Exception: javax/imageio/ImageIO
at programs._testTemplate_jsp_45._jspService(_testTemplate_jsp_45.java:311)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:142)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.runtime.JspServlet$JspServletWrapper.service(JspServlet.java:323)
at org.apache.jasper.runtime.JspServlet.serviceJspFile(JspServlet.java:503)
at org.apache.jasper.runtime.JspServlet.service(JspServlet.java:651)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)

Answer 1

Actually, it does appear that an exception is thrown, but it's not descriptive.