How to invoke a servlet generating an image ?

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fabien.moquet@gmail.com - 17 May 2007 10:33 GMT

Hello,

I am using a Servlet that generates a PNG image using JFreeChart on a
Tomcat 6.0 server.

I would like to test the servlet but in don't know how to invoke it
from my brower. I tried to open the URL http://localhost:8080/myapp/ServletBarChart
but Tomcat displays an error saying that the file could not be found.

Here is my servlet file :

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import org.jfree.chart.*;
import org.jfree.chart.plot.*;
import org.jfree.data.*;
import org.jfree.data.category.*;

public class ServletBarChart extends HttpServlet {

protected void service(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {

DefaultCategoryDataset dataset = new DefaultCategoryDataset();
dataset.addValue(120000.0, "Produit 1", "2000");
dataset.addValue(550000.0, "Produit 1", "2001");
dataset.addValue(180000.0, "Produit 1", "2002");
dataset.addValue(270000.0, "Produit 2", "2000");
dataset.addValue(600000.0, "Produit 2", "2001");
dataset.addValue(230000.0, "Produit 2", "2002");
dataset.addValue(90000.0, "Produit 3", "2000");
dataset.addValue(450000.0, "Produit 3", "2001");
dataset.addValue(170000.0, "Produit 3", "2002");

JFreeChart barChart = ChartFactory.createBarChart("Evolution des
ventes", "",
"Unite vendue", dataset, PlotOrientation.VERTICAL, true, true,
false);
OutputStream out = response.getOutputStream();
response.setContentType("image/png");
ChartUtilities.writeChartAsPNG(out, barChart, 400, 300);
}
}

What am I doing wrong ?

Fabzy

Reply to this Message

Nino - 17 May 2007 18:56 GMT

On May 17, 2:33 am, fabien.moq...@gmail.com wrote:

> Hello,
>
[quoted text clipped - 4 lines]
> from my brower. I tried to open the URLhttp://localhost:8080/myapp/ServletBarChart
> but Tomcat displays an error saying that the file could not be found.

Perhaps you do not have Tomcat set up correctly? Where did you put the
compiled file? Did you properly set up the configuration for that
folder? Is your "myapp" context set to reload when a new file is added
or do you need to restart Tomcat?

I have only worked with Tomcat 4 (and a little with 5), but I'm
assuming they are fairly similar. Everything else looks okay.

Nino

Reply to this Message

Carl - 17 May 2007 23:16 GMT

On May 17, 2:33 am, fabien.moq...@gmail.com wrote:

> Hello,
>
[quoted text clipped - 6 lines]
>
> Here is my servlet file :

--Code cut out--

> What am I doing wrong ?

Hello,

What does your web.xml look like and where is your servlet located?

For testing, I would place the servlet class in:
(note: you should really define a package for your servlet)

myapp/WEB-INF/classes/ServletBarChart.class

And add the following to your web.xml inside the <web-app> block:

<servlet>
<servlet-name>TestImage</servlet-name>
<servlet-class>ServletBarChart</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>TestImage</servlet-name>
<url-pattern>/showImage.do</url-pattern>
</servlet-mapping>

Restart the server, and you should be able to see your image using the
url:
http://localhost:8080/myapp/showImage.do

Hope that helps,
Carl.

Reply to this Message

How to invoke a servlet generating an image ?

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