Java EE (Java Enterprise Edition) General Discussion

Hi,

I am writer a JSP site for displaying JFreeChart. The main JSP page gets some parameters then the second page out put the chart as binary data with a Java class.

I've located the part which generated the error, as follows:

Code:
OutputStream os = response.getOutputStream(); <--- this line cause the error
response.setContentType("image/png");
ChartUtilities.writeChartAsPNG(os, chart, 400, 300);

(other than it, the JSP does nothing with response or out)

Error:
Servlet.service().for servlet jsp threw exception java.lang.IllegalStateException
at org.apache.jasper.runtime.ServletResponseWrapperInclude.getOutputStream(ServletResponseWrapperInclude.java:62)
at org.apache.jsp.build005f005.seriesChart_jsp.jspService(org.apache.jsp.build_005f005.seriesChart_jsp:110)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:99)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWarpper.java:325)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:245)
.....

I've searched this forum and google and seeking for solution for thousands times. But sadly, ways such as adding out.reset(); doesn't work.
Would any one has some suggestion for me? Your help is very appreciated. Thanks!