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Editorial Team
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Asked: 2026-06-04T15:55:17+00:00

OK, here is the problem I have. I have a servlet that dynamically creates

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OK, here is the problem I have. I have a servlet that dynamically creates an image (not based on parameters) which I do NOT want to save on the HDD.

I also have a HTML template (JSP) where I want to show that picture.

I create my image as following:

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    PieDataset dataset = createDataset();
    JFreeChart chart = createChart(dataset, "OS Usage");

    resp.setContentType("image/png");
    ChartUtilities.writeChartAsPNG(resp.getOutputStream(), chart, 500, 400);

    req.getRequestDispatcher("report.jsp").forward(req, resp);
}

My JSP looks like this:

<body>
    <h1>OS usage</h1>
    <p>Here are the results of OS usage in survey that we completed.<br>
    <p><img alt="OS usage" src="/reportImage">
</body>

When that code is executed, I get what I expected, from the way I wrote my code, a image only, without any html.

My question is how to do it so the HTML renders as well.

Thx.

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1 Answer

  1. Editorial Team

    You should have two servlets:

    • One to generate the HTML page (by forwarding to a JSP). This generated page contains <img src="/reportImage" .../>. When the browser sees this tag, it sends a second request, to the URL /reportImage.
    • One to generate the image, mapped to the /reportImage URL. This servlet should only send the bytes of the image to the response output stream. It must not forward to a JSP.
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