Sunday, April 8, 2012

Jamon : a quick and easy way to monitor Java web applications' performances

In this post, I would like to introduce a very handy way to monitor a Java web application's performance, using Jamon (click on the link to get to the Jamon project homepage). 

There are numerous ways to monitor the performances from a Java web application, but how easy it is set up and what kind of information you need in return, will determine the solution you'll choose. This could go from printing out (or logging) execution time, which has been explicitly calculated (stop time - start time), on the standard exit, to AOP using Spring Aspect or AspectJ.

The most interesting feature Jamon provides, is a web application showing you the monitoring's result.


  • Apache Tomcat 6.0.32
  • Jamon 2.73

How to use it (basic usage)

  1. Download Jamon distribution file
  2. Copy the jamon-2.73.jar library into the classpath of the project for which you want to enable monitoring.

    Actually, you would rather copy this library to the directory from you web server, that contains the libraries that are shared across all the deployed applications. In my case, as I deployed a sample application on a Tomcat server, I copied the jamon-2.73.jar library into the %TOMCAT_HOME%/lib directory. Also, if you intend to use the provided monitoring console, you should definitely shared the library across all the applications.
  3. Deploy the provided monitoring console by copying the jamon.war file from the Jamon distribution to the %TOMCAT_HOME%/webapps directory.
  4. Add monitoring instructions to the code section you want to watch. As an example, here's some code to illustrate a practical use of Jamon : 


import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.jamonapi.Monitor;
import com.jamonapi.MonitorFactory;

 * Servlet implementation class JamonDemoServlet
public class JamonDemoServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
 private static final Random RANDOM = new Random();
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  doGet(req, resp);

 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  String action = req.getParameter("action");

  if (action.equalsIgnoreCase("LOGIN")) {
   login(req, resp);
  } else if (action.equals("CHECKOUT")) {
   checkoutCart(req, resp);

 private void login(HttpServletRequest req, HttpServletResponse resp) throws IOException {
  Monitor mon = MonitorFactory.start("login");

  // simulating login process
  long randomProcessTime = (long) (RANDOM.nextDouble() * 1000.0);
  resp.getWriter().print("PROCESSED LOGIN REQUEST");
  try {
  } catch (InterruptedException e) {


 private void checkoutCart(HttpServletRequest req, HttpServletResponse resp) throws IOException {
  Monitor mon = MonitorFactory.start("checkout");

  // simulating cart checkout process
  long randomProcessTime = (long) (RANDOM.nextDouble() * 3000.0);
  resp.getWriter().print("PROCESSED CHECKOUT REQUEST");
  try {
  } catch (InterruptedException e) {


As you can see,  it's very simple to use Jamon : first, you'll retrieve and start a Monitor object by executing MonitorFactory.start(String label). The "label" argument designates the name under which the code section to monitor will be identified within the monitoring console. 

At the end of the code section that you're monitoring, just call the stop( ) method on the Monitor object. 

And voilĂ ...

I've deployed this sample servlet and had it process a few requests (some with the "action" parameter = LOGIN, some otheres with the value CHECKOUT. 

Monitoring console

Finally, open the Jamon monitoring console which is deployed at the following address : http://localhost:8080/jamon

Click on the "JAMon Admin Page" link and you'll be brought to the page from which you could access all the monitoring info : 

Among all the infos, you'll have the number of times your monitored code has been executed, the average execution time, the longest/shortest execution time, and so on.


You might think that Jamon is only useful during development but from my personal experience, you could deploy it along with your application into production : 
  • its footprint is practically non significative
  • you can disable/enable monitoring in one click, from the administration console
  • you can filter the monitor that you want to display in the list
That was just a slight overview of Jamon's features, you should definitely take a look at its documentation, as it provides some other monitoring functionalities.