Develop Reference

Does OSGi-as-a-Service exist?

Are there any Java PaaS solutions out there that offer OSGi containers as a service?
Google App Engine --> has their own GAE server which is modified Jetty
CloudBees --> has their own RUN#Cloud container which is modified Tomcat
OpenShift --> uses JBoss/Wildfly
??? --> uses, say, Karaf or Equinox
If not a full-blown PaaS, just a clusterable/scalable OSGi host. Google turned up nothing, so I'm assuming there isn't anything like this. Thanks in advance!

(In contrast to the other answers:) No, there is no OSGi-as-a-Service in the cloud, yet.
I am currently writing my master thesis about porting an OSGi application on a PaaS, so I did my own researches about PaaS and OSGi. I did not find any satisfying solution based on OSGi in the cloud (however I did find other solutions ;). The problem is that OSGi is pretty unpopular and the cloud is notoriously trendy.
As the other questions mentioned, OSGi is a Java library. So you could set it up pretty much everywhere where Java is supported. But that would be more a IaaS solution as a PaaS solution (which you seem to look for, as you are asking for OSGi-as-a-service). You would need to setup a OSGi framework on your own and you would have no support for deploying bundles. Which degenerates this solution pretty much. So no, there is no special cloud offer for OSGi, despite there are many for Java.
However, there is a nice book called Modular Cloud Apps with OSGi from Paul Baker and Bert Ertman published by O’Reilly. The book describes their PaaS-like solution to use OSGi in the cloud. The basically setup a repository of OSGi bundles, where they stored all their stuff. Then they created a cloud image, which only contains an empty OSGi framework/server (just like Apache Karaf, but they wrote their own tool called Apache ACE for what reason ever...). They were able to boot those images and as soon as the machine was up, they just deployed the bundles from their repository to the instance (via a web interface).
There is also a video of their demo on youtube: https://www.youtube.com/watch?v=oN3jYKOQ1Tk
I think this strategy is the best PaaS-like solution you could get. But - unfortunately - this is not supported by any cloud vendor out of the box. But you could set it up on (for exmaple) Amazon very easily.
EDIT
There also exists a Build Pack for Cloud Foundry to setup a Virgo server which can run OSGi apps: https://github.com/glyn/virgo-buildpack

Take a look at Gyrex. It's not a service yet but can be used to build you're own OSGi PaaS cluster. It uses Equinox, p2 for provisioning and Jetty.
http://eclipse.org/gyrex
Disclaimer: I'm a committer and heavy user of it.

There is a commercial provider of OSGi cloud services - Paremus. They have 2 cloud products - Nimble and Service Fabric. You might want to check them out. The Nimble product is available in a limited free edition for trial.

OSGi can be used on pretty much any cloud provider that offers Java support, since it is essentially just a Java library.
The exception to this would be Google App Engine, since they don't just modify Jetty, they modify Java itself and remove the ability to create threads and classloaders, both of which are required for full OSGi support.

OSGi is basically a Java library that can run on a virtual machine that has a JDK/JRE support. But remember one stuff, out of the box support is what you are looking for and you need to customize the PaaS you choose to run your app. I think to do this, you need to choose the provider that is easiest to configure and scale. Try out Jelastic. It is easiest of the lot to cinfigure and get started. Check their jar uploads, and I think it will suffice your needs.
Let me know what you think and if this answer is of any help.
Surya

JSP tools for a Ruby/Rails developer?

I am a full time rubyist, really enjoying rails, Sinatra, etc. Currently, however, I find myself working on a Java/TomCat/JSP project.
I was hoping someone could help me find tools, articles, books, and any other resources that will make me more comfortable?
I'm aware that Java is very different from Ruby, and the communities, likewise, are very different. That being said, all of the documentation around Java (that I have found) is a mess, and discovery is very difficult in this community.
Things I'm specifically looking for:
development environment setup tips
logger, logging, colorful output, best practice, etc
library resources and documentation
easy to navigate documentation for Java SE 6
anything you have found that makes your daily life better
Thanks!

If you are joining an existing Java project then you probably want to take a look at the tools already in use and get an existing developer / co-worker to bring you up to speed with them as a first port of call.
Having said that, here are my top tips:
Get comfortable with one of the main Java IDEs. Eclipse (my personal choice), Netbeans or IntelliJ are all excellent and very powerful tools once you get to know them. The refactoring / code navigation tools are probably better than anything you are used to in the Ruby world, they will help you a lot. Java is a lot less painful with a good IDE setup.
Learn Maven - this will take some time investment but it is extremely powerful for automating your dependency management and build process. Once you get it working you will save a huge amount of time on project / build management. Maven also provides automated access to the equivalent of Ruby gems through the various public Maven repositories.
And here are some particularly useful resources:
Java tutorials - good to get an introductory feel for the core Java libraries.
Java 6 API - useful as a reference resource for all the classes and functionality available in core Java (a lot of this is also provided via the IDEs)
JSP Documentation - for the JSP / Java EE aspects

As a little side note don't forget to learn about JSTL and Expression Language.

first of all you are on the right road to discover how elegant Java EE is. since you adressed various topics i will divide my answer into different parts :
Development environment:
Without further talk i will advise you to directly go and pick your eclipse Java EE Juno (last release) version, however if you'd like to have a look at other IDEs you can either check NetBeans 7.2 (last release) or IntelliJIDEA 11.2 Ultimate (last release i know of and that I have). Basically Eclipse has tons of plugins and features and backed up by a very great, large and passionate community.
[ i personally tried NetBeans, and IntellijIDEA, but felt more comfortable with Eclipse because of its look, features, cool color theme etc]
For JSP and HTML, CSS ,JS stuff, i however recommend the great IDE of Jetbrains Webstorm it has zen coding as well as many many other things like fast auto completion and support for many frameworks.
Lastly, pick up Sublime Text 2 as a text editor for quick edits or to just check a source file, it has a very beautiful layout and support for many languages as well as tons of plugins.
Ressources and documentations :
All the Java API specifications are available for offline viewing for free in Oracle's website and come packaged with the various SDK that are available there.
The easy to navigate documentation :
Eclipse IDE makes it very easy to attach JavaDoc and Source to the different jar files that make up a JDK, that said, your learning and coding experience will be greatly increased once you've set that up.So when you type Connection for example in IDE, you can simple hold Ctrl command then right click on it and the source code of the class implementation would be opened in a different tab. yes yes it's the power of the open source world :)
Concerning tips and tricks :
I'll recommend you use //TODO comments as Eclipse has support for them and you can setup your own TODO comments in settings, also you can use TASK comments, you've Mylyn too to manage your bugs, tasks either locally or connect to your favorite bug and issue tracker through a connector since many connectors are available for such purpose. Add to this list the possibility to configure bookmarks to help you manage your source files when they become full of lines.
About Tomcat:
Well if your goal is to make Java EE applications that do not require the advanced features of the Java EE specification, then you can use the sweet Tomcat, it's easy to use and configure and a well known web container.
However if that's not the case, and you wanna specialize in Java and spend lots of time to try to understand the ins and outs of this huge specification, you are likely to need a certified Application Server that supports all Java EE components. There are lot of them available, but since you asked for advise and I am here giving my modest suggestions I would advise you to pick the GlassFish Application Server, it's Open Source, and once you install it on Eclipse IDE for example, it will be bundled with both Java EE 5 and Java EE 6 API doc. This means no time to be wasted on browsing different tools and tabs, you will have everything grouped inside your Eclipse IDE so that you are 100% on the tasks at hand.
p.s: if you've any more questions please feel free to ping me.
Any good tip or trick :
Have fun with Java, because you will be learning everyday something new :)
p.s: i didn't mention any framework, because by the time you get used to Java EE you will be in position to pick the one that suits your needs. Also forgot to mention JUnit (Testing Framework) and a great eclipse plugin EClemma for code coverage (much better than Cobertura/eCobertura and easier to use), and of course you can try Maven as the other post mentioned, or try Apache Ant as build tool.

If you're coming from a Rails background, I'd be prepared for some initial frustration. Setting up projects in an IDE can be time consuming, and generally it's going to be more painful to get things like a basic web+app server up and running using Tomcat than using Ruby.
For a REPL, I would recommend Groovy (and indeed it comes pre-installed on Intellij) but you can also use BeanShell. Grails, or groovy on rails, is probably the closest thing we have to a Rails-like environment.
As others have said, with Java, using an IDE is really best. I like Intellij IDEA, but eclipse and NetBeans are also good.
For build and dependency management, Maven is probably as close as we have to standard, although I have heard nice things about Gradle.
There are entirely too many logging frameworks in java, use whatever your project currently uses, probably log4j or SLF4J. learn how to change log levels across the board, and also at a package level.
In terms of libraries, Google's Guava makes my life better on a daily basis.
The best "tips, tricks and general best practices" book on java is Josh Bloch's Effective Java. For documentation, the Javadoc is the authoritative source. Learn to read and write good javadocs.
For Test Driven Development, jUnit is probably the most widely used library, a very popular library is mockito, which also happens to be my favorite.

Kaazing vs jWebsocket

Can somebody please compare these two websocket servers. I have to select one of them; I need an expert opinion due to newbie in multiplayer "online" gaming. I would probably have the flash client. What challenges I could face using one over other.
thanks in advance.

Full disclosure: I work for Kaazing and I have not used jWebSocket myself.
A couple of quick points:
0) Production vs. Beta
Kaazing is production-quality software. The download link on the jWebSocket web page points me to a beta version of the product.
1) Client Technologies
Kaazing provides WebSocket libraries for multiple client technologies (JavaScript, Java, .NET/Silverlight, and Flash), It looks like jWebSocket provides JavaScript and Java. You mention you would need a Flash client and AFAIK only Kaazing provides that. jWebSocket uses Flash for emulation (see the next point).
Note: Kaazing now provides AngularJS, ReactJS, Objective-C (iOS), Xamarin (.NET with support for iOS and Android), Java, .NET, and Android clients. However support for SilverLight and Flash have been deprecated.
2) Emulation (for browsers that do not support WebSocket)
jWebSocket requires Flash, Kaazing does not.
Note that Flash emulation for secure WebSocket (wss://) requires you to open a separate port for the Flash x-domain policy file. In many enterprises this is a non-starter.
3) Protocol Support
Kaazing offers a wide range of higher-level protocols on top of WebSocket: JMS (can run against any back-end JMS message broker), STOMP, AMQP, XMPP, etc. I don't know what jWebSocket does in this space.
4) Enterprise Deployment
It is easy to configure the Kaazing WebSocket Gateway in conjunction with existing Directory services (LDAP). It supports Single Sign-On, and the gateway can easily be clustered for HA purposes (again, not quite sure what jWebSocket does here.)
Please take a look at the documentation for these features:
Security configuration:
Using the Gateway to Support High Availability
Secure Network Traffic with the Gateway
5) Open Source
jWebSocket is open source, Kaazing has both an open source Community Edition and an Enterprise Edition.
Hope this helps for now!

I am a jWebSocket developer, we are currently working in the first production version of jWebSocket, I will just mention some advantages of jWebSocket:
- Multiple clients ( JavaScript, C#, Java OS, BlackBerry, Android, GWT(In process), and some others ).
- Multiple WebSocket engines, just switch and run in the configuration, among them (Grizzly-GlassFish, Tomcat, TCP, NIO...) in order to become jWebSocket more widely used and make applications easier to be migrated.
- NFC and SmartCards, Arduino and other technologies.
- A very variated set of Demos in the client side (Games, Chat, sms, WebSocket-Captcha, Sencha, Jquery & jQuery Mobile plugIns, Arduino, Smartcard, SessionStorage, SSH-Remote Shell Control RT in the web, a Ping Pong Game demo, Channels to create full client side applications without need a server side plug-ins, etc... )
We have been working during a long time in a new Documentation, a new Web Site and a new Production release of jWebSocket for our community, jWebSocket is a project created by people from all the world who dedicate their free time to contribute and create a really usable product to be used by all the opensource community. We are trying to give our best to the community.
I wouldn't establish a comparison between Kaazing and jWebSocket, they both have different communities, goals and LICENSES.

For a gaming platform you might want to check out http://www.pubnub.com/. I met their CTO at a developer conference and for your stated purpose, you might just win big with not having to manage the infrastructure on your own. Check out their http://www.pubnub.com/customers/showcase for details on who is using their infrastructure and for what purpose.

For me, the main point is Kaazing has a proprietary license and it's payed. jWebSocket is LGPL and free. If you are developing an application with an ROI that allows you to pay for a service like Kazzing, I think it is a good option (like pubnub.com and pusher.com), but if you want to build a complete solution and host it or you want to contribute with OS community to create a new websocket alternative, jWebSocket is an excellent option.

There are two things I would add to Peter's comment, one is that Kaazing's emulation solution exposes identical APIs to the native WebSocket APIs, so you only have to learn WebSocket not some other proprietary API. You can check out the demos and the doc that Peter referred to for more information.
Secondly, Kaazing just announced the availability of Kaazing WebSocket Gateway AMIs on Amazon EC2 - http://kaazing.com/cloud
Best,
Jonas

I've been working with jWebSockets for the past 3 months or so, and this is the first I hear of Kaazing.
I will describe how I feel about jWebSocket so far to the best of my ability in the hope that it will help.
Setting up the developing environment and getting started wasn't easy but developing using it is rather comfortable. The entire system makes sense and it is quite easy to understand. You program with Java on the server side and js on the client using json based tokens, it makes it very easy to send and receive data.
It is however very lacking in support. There are a lot of missing documentation and the support forum is nearly dead. There is payed support from the developers but I've never tried it.
There are a lot of open source demos that you can use to understand and get started. Most of them were working smoothly. Something I cannot say about kaazing after a brief visit to their demo site.
In the few months I've been working with jWebSocket I've yet to encounter a single bug, The system works smoothly and my only disappointment is the lack of support and documentation.

If you are looking for a pure open source project, look at the Atmosphere Framework. License is Apache 2.
-- Jeanfrancois (creator of Atmosphere)

jWebSocket is a good framework and support almost all servers. It has support of jetty too. Only problem with jWebSocket is slow development and zero support. Websocket specification are changing very rapidly and jWebSocket releases are very slow. I would prefer to wait and watch jWebSocket framework for some time.

Spring surf and webscripts projects disambiguation

I recently came across spring surf project and Spring webscripts .
Both these technologies (I guess) seem to come from Alfresco developers
Web Scripts
Surf
Is it correct ?
As I was investigating both of them couple of hours, it seems to be very clever technology. Little bit focused on CMS, but it makes better impression and sense than JSPs, Icefaces (which I haven't liked for many years, but I've been forced to use them).
It's a shame that both technologies are in state of incubation within springsource.
Could please anybody who has experience with them tell us some stories from production use ?
I noticed that Surf can be used together with Spring Roo. Is there any other support, like maven, IDE etc ?

Yes, those technologies were developed by Alfresco and then donated to Springsource to detach them from Alfresco and become first-class web development libraries.
I'm not aware of any remarkable use of those libraries out of the Alfresco scope, but that's most likely because of my current focus being on Alfresco, or because they are still quite new as standalone projects.
Have a look at Alfresco Share or the Web QuickStart to see how web scripts and Surf are used to create fully functional and standalone applications.
Spring Surf and web scripts are built with maven and deployed into Alfresco maven repository, which should give you enough support for your maven builds. I'm not aware of any maven archetype for Surf or web scripts.
As per developer tools, I'm only aware of Spring Roo. The official documentation could bring some more information, though.

Java EE App Server Hello World

I am fairly comfortable with standalone Java app development, but will soon be working on a project using a Java EE application server.
Does anyone know of a straightforward how-to tutorial to getting a hello-world type application working in an application server? I'm (perhaps naievly) assuming that the overall approach is similar between different frameworks, so I'm more interested in finding out the approach rather than getting bogged down in differences between the different frameworks.
If you are not aware of a good guide, then could you post bullet-point type steps to getting a hello-world running?, i.e.
Download XX
Write some code to do YY
Change file ZZ
Other steps...
Note: Just because I have a windows machine at home, I would prefer to run if this could be run on windows, but in the interest of a better answer, linux/mac based implementations are welcome.

I would choose JBoss AS or GlassFish for a start. However I'm not sure what you mean by Java EE "Hello World". If you just want to deploy some JSP you could use this tutorial (for JBoss):
http://www.centerkey.com/jboss/
If you want to get further and do the EJB stack and/or deploy an ear-file, you could read the very good JBoss documentation:
Installation Guide
Getting started
Configuration Guide
In general you could also just do the basic installation and change or try the pre-installed example applications.
I currently have JBoss installed (on windows). I develop with Eclipse and use the Java EE server integration to hot deploy or debug my code. After you get your first code running you realy should have a look at the ide integration since it makes development/deploy roundtrips so much faster.

The JavaEE (they dropped the 2) space is pretty big. A good tutorial to start is the one from Sun. For a simple hello world application, the web container only would suffice. A well known servlet jsp container is tomcat. See here for installation instructions. Try installing it with eclipse and create a web project. This will generate some files for you that you can look at and edit. Also starting and stopping the application server is simpler.

Another option is to get Oracle JDeveloper (free to download and use - it's a full featured IDE that includes some neat extras like the SQL workbench and BPEL designer).
As a learning tool, it is quite good, not only for the tutorials available from Oracle, but it includes a range of "cue-card" lessons in the tool itself to teach many common techniques.
cue card view http://tardate.heroku.com/images/jdev-cuecards.jpg

If you haven't gone near NetBeans in a while its catching up with Eclipse very fast and worth a look, especially when starting Java EE.
Version 6.x installs Tomcat and/or Glassfish for you and then provides wizards to create/deploy/redeploy applications.
The initial tutorial on Web Applications is here and a more complex example here.

As JeroenWyseur puts it, Java EE is a fairly big space. In addition to what he said, you should try to get more details of what exactly you'll be doing: servelts & co, EJB (entity, session, message beans?) and try to get familiar with that.
It should be clear for you that your code runs in a managed environment, which imposes a lot of constraints. in order to make sure you understand what happens you should get familiar with the concept of deployment. Then, if you do EJBs, transaction management is important too. If you don't understand exactly what happens when a bean or a servlet is deployed, how transactions are managed, how beans are invoked, you're going to have a hard time.
A book that helped me a lot back in the time is Mastering EJB, by Ed Roman.
Also, getting familiar with RMI will help you understand EJBs.