Saving a PNG file on a server in a Java bean, using JSTL

Question

I am writing an update page in JSTL where the user inputs some numbers. I then call a java bean - passing the numbers as parameters - which, using JFreeChart, creates a PNG

Answer 1

Write it to the directory path returned from System.getProperty("java.io.tmpdir");

Answer 2

I would suggest that you use the ServletUtilities class. It saves in the java tempdir AND cleans up when the session is invalidated. :) Another hint for then displaying the file is to use the DisplayChart servlet to get your images. This goes in web.xml

      <servlet>
    <servlet-name>DisplayChart</servlet-name>
    <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
  </servlet>
   <servlet-mapping>
        <servlet-name>DisplayChart</servlet-name>
        <url-pattern>/servlet/DisplayChart</url-pattern>
    </servlet-mapping>

This is then how you display the image using jstl:

<img src="<c:url value='/servlet/DisplayChart?'><c:param name='filename' value='${yourFileNameHERE}' /></c:url>" alt=""/>