What a Year! Phew..

-- Art by Baran

Happy Holidays!

I am a Hindu by faith. but I love christmas, for the sense of good it cultivates in you (or atleast thats what it attempts). I am big sucker for those 25 days to Chirstmas on ABC, and the movies of that genre..

Having said that I have my own (small) list for Santa..

Love, Peace, Harmony, Health and Success.

For

Me, My Family, Friends, My Country, and the whole World.

I am sure I have been nice all year, and Santa Obliges..

So be good for Goodness sake..

Happy Holidays!

image by mcgraths

Using Equinox CommandProvider to make OSGi console interactive.

After fiddling with the First Bundles that "Hello World"-ed upon Activation, You want to see more interactivity in OSGi. Although Using OSGi for an interactive Command Line Application would be like this one would be, well, a callable over-kill, I am going to start with an example and Expand it in later posts. So, please Welcome CommandProvider.

CommandProvider is an EQUINOX specific API for extending the Console. This basic Example illustrates how to get a command from console and do something in java and also gets your feet wet on Service Registry

package com.so.examples.commandconsole;

import org.eclipse.osgi.framework.console.CommandInterpreter;
import org.eclipse.osgi.framework.console.CommandProvider;

public class DisplayMessageCommand implements CommandProvider {

 public void _say(CommandInterpreter ci) {
  ci.print("You said:" + ci.nextArgument());
 }

 @Override
 public String getHelp() {
  return "\tsay - repeats what you say\n";
 }

}

This provider class implements CommandProvider, which is actually just a marker interface, except that getHelp is a helper to print out additional help data when user types in help. The actual commands follow the java reflection pattern as a method that starts with an underscore(_), takes CommandInterpeter as parameter and returns void. So there can be more than one command provided by one CommandProvider Class. Important thing here is, this could have been easily(, better) achieved with annotations, but OSGi inherently is for ALL java platforms, so its implemented this way.

Next step is to tell the framework to commands from this CommandProvider. To do that, We have to "bind" this to framework as a service. You could do it anytime you have access to the bundle context, but the easiest place is when starting the bundle. An Activator like the one below should do.

public class CommandBundleActivator implements BundleActivator {

 @Override
 public void start(BundleContext context) throws Exception {
  context.registerService(CommandProvider.class.getName(),
    new DisplayMessageCommand(), null);

 }
//stripped ...

Notice that we are using equinox specific packages, so in our manifest, we add, along with the Activator

Bundle-Activator: com.so.examples.commandconsole.CommandBundleActivator
Import-Package: org.osgi.framework,
 org.eclipse.osgi.framework.console

What happens under the hood: Equinox when started with -console parameter, starts the framework also initiating a default CommandProvider Service Implementation (ignoring -console will not start the console, hence exitting back to shell). Which is the one that accepts the commands and performs actions. And EQUINOX, provides a way to extend it by adding other Implementations of CommandProvider to the ServiceRegistry.

Now start up the framework, install the new bundle, and start it,

osgi> help
 say - repeats what you say
---Eclipse Runtime commands---
 diag - Displays unsatisfied constraints for the specified bundle(s).
 enableBundle - enable the specified bundle(s)
#stripped off..
osgi> say Sarath
You said:Sarath

This brings to the next topic, which I will discuss in the next post, The Service Registry. The example project is available here.

OSGi: Starters Guide for Install, Update and Refresh Bundles

In OSGi, with a Bundle you could Install, Update or Refresh. There is a subtle difference in all these three. Just enough for a beginner to entangle the mind. To help, This post gives an a practical insight. I recorded the commands and thier out puts.

To Begin with, Install puts a bundle in the framework runtime. It also records the file location (on FileSystem or URL). It doesnot start or resolve dependents on it.

sarath@sar-akshaya:~/zbin/equinox$ ls
bundles  equinox.jar  org.eclipse.osgi_3.4.0.v20080605-1900.jar
sarath@sar-akshaya:~/zbin/equinox$ ls bundles/
FirstBundle-1.0.0.jar   SecondBundle-1.0.0.jar  
sarath@sar-akshaya:~/zbin/equinox$ java -jar equinox.jar -console

osgi> ss

Framework is launched.

id State       Bundle
0 ACTIVE      org.eclipse.osgi_3.4.0.v20080605-1900

osgi>  install file:bundles/FirstBundle-1.0.0.jar
Bundle id is 1

//Try starting 
osgi> start 1
org.osgi.framework.BundleException: The bundle could not be resolved. Reason: Missing Constraint: Import-Package: com.so.samples.osgi.second; version="0.0.0"
 at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:305)
 at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:265)
 at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:257)
 at org.eclipse.osgi.framework.internal.core.FrameworkCommandProvider._start(FrameworkCommandProvider.java:257)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.eclipse.osgi.framework.internal.core.FrameworkCommandInterpreter.execute(FrameworkCommandInterpreter.java:150)
 at org.eclipse.osgi.framework.internal.core.FrameworkConsole.docommand(FrameworkConsole.java:302)
 at org.eclipse.osgi.framework.internal.core.FrameworkConsole.console(FrameworkConsole.java:287)
 at org.eclipse.osgi.framework.internal.core.FrameworkConsole.run(FrameworkConsole.java:223)
 at java.lang.Thread.run(Thread.java:619)

osgi> diag 1
file:bundles/FirstBundle-1.0.0.jar [1]
  Direct constraints which are unresolved:
    Missing imported package com.so.samples.osgi.second_0.0.0.

osgi> install file:bundles/SecondBundle-1.0.0.jar
Bundle id is 2

osgi> ss

Framework is launched.

id State       Bundle
0 ACTIVE      org.eclipse.osgi_3.4.0.v20080605-1900
1 INSTALLED   com.so.samples.osgi.FirstBundle_1.0.0
2 INSTALLED   com.so.samples.osgi.SecondBundle_1.0.0

//Try starting Again
osgi> start 1
org.osgi.framework.BundleException: The bundle could not be resolved. Reason: Missing Constraint: Import-Package: com.so.samples.osgi.second; version="0.0.0"
 at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:305)
 at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:265)
 at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:257)
 at org.eclipse.osgi.framework.internal.core.FrameworkCommandProvider._start(FrameworkCommandProvider.java:257)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.eclipse.osgi.framework.internal.core.FrameworkCommandInterpreter.execute(FrameworkCommandInterpreter.java:150)
 at org.eclipse.osgi.framework.internal.core.FrameworkConsole.docommand(FrameworkConsole.java:302)
 at org.eclipse.osgi.framework.internal.core.FrameworkConsole.console(FrameworkConsole.java:287)
 at org.eclipse.osgi.framework.internal.core.FrameworkConsole.run(FrameworkConsole.java:223)
 at java.lang.Thread.run(Thread.java:619)

osgi> diag 1
file:bundles/FirstBundle-1.0.0.jar [1]
  Direct constraints which are unresolved:
    Missing imported package com.so.samples.osgi.second_0.0.0.

Refresh resolves dependencies. If run on a bundle with an active dependent, it refreshes the dependents too. If a bundle has an activator, It stops and restarts.

osgi> refresh 1

osgi> ss   

Framework is launched.

id State       Bundle
0 ACTIVE      org.eclipse.osgi_3.4.0.v20080605-1900
1 RESOLVED    com.so.samples.osgi.FirstBundle_1.0.0
2 RESOLVED    com.so.samples.osgi.SecondBundle_1.0.0

osgi> start 1
Started Bundle:From Second 1.0.0

osgi> shutdown
Stopped Bundle:From Second 1.0.0

osgi> close

sarath@sar-akshaya:~/zbin/equinox$ java -jar equinox.jar -console

osgi> Started Bundle:From Second 1.0.0

osgi> ss

Framework is launched.

id State       Bundle
0 ACTIVE      org.eclipse.osgi_3.4.0.v20080605-1900
1 ACTIVE      com.so.samples.osgi.FirstBundle_1.0.0
2 RESOLVED    com.so.samples.osgi.SecondBundle_1.0.0

osgi> packages 1
No exported packages

osgi> packages 2
com.so.samples.osgi.second; version="0.0.0"
  file:bundles/FirstBundle-1.0.0.jar [1] imports

//make change 1.0.1
osgi> install file:bundles/SecondBundle-1.0.0.jar        
Bundle id is 2

osgi> stop 1
Stopped Bundle:From Second 1.0

osgi> start 1
Started Bundle:From Second 1.0

osgi> refresh 2
Stopped Bundle:From Second 1.0
Started Bundle:From Second 1.0

osgi> stop 1
Stopped Bundle:From Second 1.0

Update just RE-puts the bundle into framework. This is slightly different from install, that you can ONLY update a bundle with same [Bundle-SymbolicName:Bundle-Version] combination. Meaning-- You cannot Install a same jar (same uri or different) or an updated jar(new code) with the same combination. You only have to UPDATE it in the framework. Update can be done by the BundleId in the runtime. To update with a Different jar (uri is different)

osgi> update 2 

osgi> refresh 2

osgi> Stopped Bundle:From Second 1.0
Started Bundle:From Second - 1.0.0 update

osgi> update 1
Stopped Bundle:From Second - 1.0.0 update
Started Bundle:From Second - 1.0.0 update

osgi>update 1 file:bundles/newfirst.jar //with same symname:version combo
Stopped Bundle:From Second - 1.0.0 update 
Started Bundle:From Second - 1.0.0 update 

Hope this helps.. Read more on Osgi

Days after Nov 26 2008

I wish this long weekend never happened in time. No less than 200 people were reported killed in terror attacks in Mumbai, India. I was driving to new york when I first heard about the reports on NPR at around 3 in the after noon. The death toll reported was ~50. For a year like 2008, in which there had been blasts almost every fortnight, this initially did not come to strike me as hard as it did with every 10 minutes of passing time. The number slowly jumped to 70s and then to 100 by the time I lost NPR signal on my car.


By the end of the evening, I reached New Jersey, stayed over at my uncles place. From then, till late night, I was glued to Indian news channels on TV. NDTV and IBN live on the internet. Words cant explain the state of mind watching those gory initial pictures and videos of the happenings. State of dismay, panic and confusion reined through out the night. All the while, There was only one question. What in the world is a Country doing when handful terrorists have been doing so much so fast?

Every one likes to point fingers. TV channels on Govt. Govt on Pakistan. WHERE is Accountability? TV channels have a lot easier job to stand on the ring and comment. They have emotional voice over guys just in time to describe the even as they happen. They even go as far as showing NSG operations LIVE! One Channel has been quick enough to get animations and background sound to get viewers *into it*. NO discretion what so ever.

Govt. The less I talk the better. They gave the worst answer to this frenzy situation. Dumb stuck, Clue less and USELESS.

Last but not the least, The Intelligence. These people's JOB is to get to this situations in timely manner. To be prepared for counter attacks. To negotiate. TO get the crooks to negotiate. To be prepared with Contingency. A, B and C. To protect as many people as they can. To catch the evidence live if possible. NOTHING. With all due respect to all the policemen who were fighting and Sincere devotion to those who laid down thier lives in the line of duty, The heads, chiefs and stragergiest, You FAILED. The Administration You FAILED. The Elected Governments at State and Center you FAILED.

217, as of now. Only 10 inhumans to do it all. FARMERS in US can take them down in no time (some commenter in another board). The so called PRASASAN, Shame on you for not having the mettle. Shame on you for being lethargic. Shame on you for not understanding the gravity of the situation. There is only one thing that separates you and the terrorists themselves - MOTIVE. You are as much responsible, until you pay back.

May Peace Prevail.