radioAe6rt

Here are some lite mods to the Apache XML-RPC v3 code that allow you to take explicit control of initializing your user handlers when used inside a Java servlet.

In this new scheme, a handler artifact declared in XmlRpcServlet.properties

artifact=mypackage.Handler

must implement the (new, proposed) UserHandler interface

package org.apache.xmlrpc.server;

import javax.servlet.http.HttpServlet;

public interface UserHandler {
   public void init(HttpServlet s);
}

In your servlet init() method, we acquire the reference to the handler and allow it to do whatever configuration it should do before requests are made of it.

public class MyServlet extends XmlRpcServlet {
   ...
   public void init() {
      // put useful stuff in ServletContext here...
      // then init the handler
      getUserHandler("artifact").init(this);
      ...
   }
   ...
}
 

Without the init hooks, and because the Handler is instantiated within the parent class servlet constructor, you have no way of preparing the handler in a special way before the servlet begins taking requests.

The model I’ve hinted at here suggests that prior to calling init() on the user handler, you have put useful things in the servlet context for handler.init()’s consumption and use. Acquiring inherited Log4J logger instances and DataSource instances come to mind.

There may be a good way to do what my mods do — without the mods — but I couldn’t immediately see it.

[tags]xmlrpc,xmlrpcservlet,servlet[/tags]

There is Good News in the IP voice services world this morning. It’s not new news to some of us, but to many I know it is.

The Good News is that the rest of us have been invited into The Big House. The Big House where you don’t need Session Border Controllers, Media Gateways, or a room-filling Advanced Intelligent Network platform. Or captive customers. You don’t need any of these to be a member of the Voice 2.0 producer economy.

All you need is an XML-RPC server process. And Java or Perl or Python or Ruby or Groovy, or whatever scripting language in which you think and which makes you happy.

Then, implement your philosophy.

Take an award winning company like Televolution, to whom I consult [disclaimer], that wants to send you as a developer voice event and signalling data, and award winning Iotum with their call relevance brainchild, and we’ve two companies with complementary services who have shown the way.

And it goes like this: Bob is a customer of both PhoneGnome and Iotum. Bob as an Iotum subscriber is continuously relaying his state and availability information to his Iotum service, via a network plugin that monitors his Outlook calendaring and MSN Messenger state. Bob has also configured call routing rules in his Iotum service. When a call comes in for Bob on his PhoneGnome line, PhoneGnome sends a short XML-RPC message to the Iotum server indicating who is calling Bob. The Iotum server applies Bob’s rules to his realtime state, and instructs PhoneGnome in a simple XML-RPC response in how to dispose of the call: desk phone, mobile phone, or voicemail. Bob takes control of where, when, and under what conditions his calls are terminated.

Because we are programmers, let’s look at the two messages that pass between the PhoneGnome and Iotum platforms on the wire.

Given an inbound call from 9185551212 to Bob at 8165551212, PhoneGnome sends, in realtime

<?xml version="1.0"?>
<methodCall>
  <methodName>theMethod</methodName>
  <params>
    <param>
      <value>
        <struct>
          <member>
            <name>From</name>
            <value>
              <string>"9185551212" <sip:9185551212@televolution.net></string>
            </value>
          </member>
          <member>
            <name>Contact</name>
            <value>
              <string>PHONEGNOME TEST</string>
            </value>
          </member>
          <member>
            <name>To</name>
            <value>
              <string>8165551212</string>
            </value>
          </member>
        </struct>
      </value>
    </param>
  </params>
</methodCall>

and after applying Bob’s rules, Iotum replies

<?xml version="1.0"?>
<methodResponse>
  <params>
    <param>
      <value>
        <struct>
          <member>
            <name>action</name>
            <value>
              <string>ACCEPT</string>
            </value>
          </member>
        </struct>
      </value>
    </param>
  </params>
</methodResponse>

In this ACCEPT example, Iotum tells Phonegnome to put the call through its normal processing. But it could have been REDIRECTed had Bob’s rules indicated it.

That’s it. PhoneGnome doing what it does best, Iotum doing what it does best, and both doing that best extremely well because the technology and federation allow that focus.

Two text messages announce the Good News: if you know any language for which there exists an XML-RPC implementation — and they are many — you are a member of the modern Voice over IP developer community.

For the first hundred years of voice telephony, you were not invited. You didn’t have the money. You didn’t own a Network.

Welcome. You are now invited — we have running code to prove it.

[tags]phonegnome,iotum,voip,xmlrpc[/tags]

A user interested in the PhoneGnome midlet pointed out something interesting and quite useful today: how to induce a Java MIDP2.0 phone to dial out under MIDlet control.

The Javadoc for MIDlet.platformRequest(String URL) says

See also this link for additional discussion.

Very cool.

Thanks, Richard.

[tags]jme,j2me,midp,phonegnome[/tags]

Roll your own XML-RPC servlet using Apache XML-RPC v3.0.

The essentials:

The servlet.

The build.xml file.

The web.xml file.

The XmlRpcServlet.properties file, which defines which of your classes handle which remote method calls.

The handler class for this example.

And finally, the Log4J log4j.properties file, which I always deploy early in this sort of project - because I know I will eventually want it. See initLogger() in servlet.init(). The log4j.properties and initLogger() method immediately allow for the creation of rolling appenders for log output to a disk file.

You will also need the ws-commons jar file. This is an unsettling URL, what with the string literal SNAPSHOT in it. If anyone has a better version that bespeaks stability, I would appreciate knowing. It was the only jar of its type I could find to satisfy the VM (argh).

Here is what the war file looks like after ant dist

images/
META-INF/
META-INF/MANIFEST.MF
WEB-INF/
WEB-INF/classes/
WEB-INF/classes/org/
WEB-INF/classes/org/apache/
WEB-INF/classes/org/apache/xmlrpc/
WEB-INF/classes/org/apache/xmlrpc/webserver/
WEB-INF/classes/org/apache/xmlrpc/webserver/XmlRpcServlet.properties
WEB-INF/classes/org/carpediem/
WEB-INF/classes/org/carpediem/phonegnome/
WEB-INF/classes/org/carpediem/phonegnome/crm/
WEB-INF/classes/org/carpediem/phonegnome/crm/Handler.class
WEB-INF/classes/org/carpediem/phonegnome/crm/log4j.properties
WEB-INF/classes/org/carpediem/phonegnome/crm/PGXMLRPCServer.class
WEB-INF/lib/
WEB-INF/lib/log4j-1.2.13.jar
WEB-INF/lib/ws-commons-util-1.0-SNAPSHOT.jar
WEB-INF/lib/xmlrpc-3.0a1.jar
WEB-INF/web.xml

The war file is copied, of course, into /webapps of your servlet container (e.g., Tomcat, jetty), and the container started.

The resulting example servlet can service a remote call of the form crm.inBound(string1,string2).

[tags]xmlrpc,xml-rpc,servlet,tomcat[/tags]

Something that deserves more attention that it gets: running Tomcat in a chroot jail.

Update: 5/11/2006

Some notes on following the Brittain/Darwin procedure from their fine book referenced above.

The platform: SuSe 8.2

• In addition to what ldd java outputs, I needed /lib/libm.so.6 because libjvm.so needed it. I also needed /lib/libnsl.so.1.
• I had to do cd /usr/local/chroot; mkdir proc; mount –bind /proc proc. This is unsettling, but the jvm needs access to /proc to start. Otherwise you get find_vma failed when the vm attempts to start. I’m not sure this mount step is staying in my process, but for now it’s there. I’d love to hear from anyone who knows of a better way to deal with this.

/usr/local/bin/jbchroot -U tomcat -- /usr/local/chroot /strace /usr/local/jdk1.5.0_06/bin/java -version > /tmp/strace.out 2>&1

#!/usr/bin/perl -w

use Uniq;  #  See http://search.cpan.org/~syamal/Uniq-0.01/Uniq.pm

while( ) {
   if( /^open\(\"(.*)\".*ENOENT/ ) {
     push @files, "$1";
   }
}

foreach $j (uniq (sort @files) ) {
   if ( -e $j ) {
      print "$j ";
      $r = `file $j`;
      chop($r);
      print $r . "\n";
   }
}