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May 19, 2009

A very quick, easy to embed, web management interface for Java

I've been trying to come up with a very simple way of managing a Java-based server application i've written.

My first port of call was JMX, which worked very well locally (using JConsole)  but it seems RMI requires ports both-ways and this limits it's usefulness over the internet, as i'd ideally like to manage the server (should the need arise) from my G1.

Next step was to try using the HttpAdaptor from MX4J, which worked fairly well but meant I really needed to code up a web interface to connect to it and that was a little more work than i'd anticipated.

On a side note, an awful lot of projects dealing with JMX seem to have been discontinued or abandoned. Even Sun's own OpenDMK seems to have been last released in 2007.

With those options discarded, I present, Trivial Manager!

It's designed to be very easy to embed (the servlet is a single Java class). Essentially, you create two things:

# A Java Interface to describe the methods you wish to present in the management app
# A Java class implementing the above management app

You then create the Servlet, passing the interface and an instance of the object to it in the constructor.

You may ask, how is embedding a servlet in to your application a quick solution? That's where Jetty comes to the rescue.

As an example of embedding Jetty and using TrivialManager, here is a few bits of code:

public interface TestInterface
   public void doSomething() throws Exception;
   public Collection<String> getSomethings();
   public int startParty(String name);
   public void countPeople(int whiskers);
   public Map<String,Integer> getIDs();

public class TestClass implements TestInterface
   public void countPeople(int whiskers)
       System.out.println("Whiskers: " + whiskers);

   public void doSomething() throws Exception
       System.out.println("Call to doSomething");
       throw new Exception();

   public Collection<String> getSomethings()
       List<String> vals = Arrays.asList("Testing", "Lalala", "1231223523", "Foomoo");
       return vals;

   public int startParty(String name)
       return 42;

   public Map<String, Integer> getIDs()
       Map<String,Integer> map = new HashMap<String,Integer>();
       map.put("foo", 123);
       map.put("rgaehre", 426432643);
       return map;

and finally, here's what goes in to your main code:

Server server = new Server(8080);
Context root = new Context(server, "/", Context.SESSIONS);
root.addServlet(new ServletHolder(new TrivialManagerServlet<TestInterface>(TestInterface.class, new TestClass())), "/*");

The end result is:

Trivial Manager screenshot

TrivialManager currently supports taking Integer, Double and String parameters.. and returning anything with a String representation, as well as Maps and Collections, which it renders as tables. I leave security and authorisation as an exercise to the reader.

The code is available:

You'll want to grab Jetty too (jetty.jar and jetty-uti.jar will need to be in your classpath).

The TrivialManager code is under MIT. Enjoy.

Most recent comments

  • yeah agree with jules need some cover may b some plants or rock work or those fry will quickly b eat… by carl on this entry
  • well by the time u get this they should of hatched lol …. id put some cover in ur tank looks abit … by Jules on this entry

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