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• Akka react vs receive

  - by Will I Am

  I am reading my way through Akka tutorials, but I'd like to get my feet wet with a real-life scenario. I'd like to write both a connectionless UDP server (an echo/ping-pong service) and a TCP server (also an echo service, but it keeps the connection open after it replies). My first question is, is this a good experimental use case for Akka, or am I better served with more common paradigms like IOCP? Would you do something like this with Akka in production? Although I understand conceptually the difference between react() and receive(), I struggle to choose one or the other for the two models. In the UDP model, there is no concept of who the sender is on the server, once the pong is sent, so should I use receive()? In the TCP model, the connection is maintained on the server after the pong, so should I use react()? If someone could give me some guidance, and maybe an opinion on how you'd design these two use cases, it would take me a long way. I have found a number of examples, but they didn't have explanations as to why they chose the paradigms they did.

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• System.out.println() does not operate in Akka actor

  - by faisal abdulai

  I am kind of baffled by this encointer. I am working an akka project that was created as a maven projecct and imported into eclipse using the mvn eclipse:eclipse command. the akka actor has the system println method just to make it easy to do read the functions and methods invoked. However any time I run the akka system, the println command does not print any thing to the eclipse console but I do not get any error messages. does any one have any idea about this. below is a code snippet. public class MasterActor extends UntypedActor { /** * */ ActorSystem system = ActorSystem.create("container"); ActorRef worker1; //public MasterActor(){} @Override public void onReceive(Object message) throws Exception { System.out.println(" Master Actor 5"); if(message instanceof GesturePoints) { //GesturePoints gp = (GesturePoints) message; System.out.println(" Master Actor 1"); try { worker1.tell(message, getSelf()); System.out.println(" Master Actor 2"); } catch (Exception e) { getSender().tell(new akka.actor.Status.Failure(e), getSelf()); throw e; } } else{ unhandled(message);} } public void preStart() { worker1 = getContext().actorFor("akka://[email protected]:2553/user/workerActor"); } } don't know whether it is a bug in eclipse. thank you.

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• Akka framework support for finding duplicate messages

  - by scala_is_awesome

  I'm trying to build a high-performance distributed system with Akka and Scala. If a message requesting an expensive (and side-effect-free) computation arrives, and the exact same computation has already been requested before, I want to avoid computing the result again. If the computation requested previously has already completed and the result is available, I can cache it and re-use it. However, the time window in which duplicate computation can be requested may be arbitrarily small. e.g. I could get a thousand or a million messages requesting the same expensive computation at the same instant for all practical purposes. There is a commercial product called Gigaspaces that supposedly handles this situation. However there seems to be no framework support for dealing with duplicate work requests in Akka at the moment. Given that the Akka framework already has access to all the messages being routed through the framework, it seems that a framework solution could make a lot of sense here. Here is what I am proposing for the Akka framework to do: 1. Create a trait to indicate a type of messages (say, "ExpensiveComputation" or something similar) that are to be subject to the following caching approach. 2. Smartly (hashing etc.) identify identical messages received by (the same or different) actors within a user-configurable time window. Other options: select a maximum buffer size of memory to be used for this purpose, subject to (say LRU) replacement etc. Akka can also choose to cache only the results of messages that were expensive to process; the messages that took very little time to process can be re-processed again if needed; no need to waste precious buffer space caching them and their results. 3. When identical messages (received within that time window, possibly "at the same time instant") are identified, avoid unnecessary duplicate computations. The framework would do this automatically, and essentially, the duplicate messages would never get received by a new actor for processing; they would silently vanish and the result from processing it once (whether that computation was already done in the past, or ongoing right then) would get sent to all appropriate recipients (immediately if already available, and upon completion of the computation if not). Note that messages should be considered identical even if the "reply" fields are different, as long as the semantics/computations they represent are identical in every other respect. Also note that the computation should be purely functional, i.e. free from side-effects, for the caching optimization suggested to work and not change the program semantics at all. If what I am suggesting is not compatible with the Akka way of doing things, and/or if you see some strong reasons why this is a very bad idea, please let me know. Thanks, Is Awesome, Scala

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• Is Akka a good solution for a concurrent pipeline/workflow problem?

  - by herpylderp

  Disclaimer: I am brand new to Akka and the concept of Actors/Event-Driven Architectures in general. I have to implement a fairly complex problem where users can configure a "concurrent pipeline": Pipeline: consists of 1+ Stages; all Stages execute sequentially Stage: consists of 1+ Tasks; all Tasks execute in parallel Task: essentially a Java Runnable As you can see above, a Task is a Runnable that does some unit of work. Tasks are organized into Stages, which execute their Tasks in parallel. Stages are organized into the Pipeline, which executes its Stages sequentially. Hence if a user specifies the following Pipeline: CrossTheRoadSafelyPipeline Stage 1: Look Left Task 1: Turn your head to the left and look for cars Task 2: Listen for cars Stage 2: Look right Task 1: Turn your head to the right and look for cars Task 2: Listen for cars Then, Stage 1 will execute, and then Stage 2 will execute. However, while each Stage is executing, it's individual Tasks are executing in parallel/at the same time. In reality Pipelines will become very complicated, and with hundreds of Stages, dozens of Tasks per Stage (again, executing at the same time). To implement this Pipeline I can only think of several solutions: ESB/Apache Camel Guava Event Bus Java 5 Concurrency Actors/Akka Camel doesn't seem right because its core competency is integration not synchrony and orchestration across worker threads. Guava is great, but this doesn't really feel like a subscriber/publisher-type of problem. And Java 5 Concurrency (ExecutorService, etc.) just feels too low-level and painful. So I ask: is Akka a strong candidate for this type of problem? If so, how? If not, then why, and what is a good candidate?

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• Scala 2.8 Actor design document? Akka design document?

  - by Stefan K.

  Is there a design document for Scala 2.8 Actors, like it is for 2.7? Scala Actors: Unifying Thread-based and Event-based Programming Is there one for Akka? The "Scala Improvement Documents Library" doesn't mention Actors.

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• Scala 2.8 Actors

  - by Dave

  Hi, We're looking at using actors in our Scala code quite soon. We're also thinking of moving to Scala 2.8 in the next few weeks. We've been keeping an eye on Akka but it doesn't currently support 2.8 and plans for it have slipped from the 0.7 release to 0.8 We would like distributed, supervised actors. Is there an alternative to Akka? Or does anyone know if Akka 0.8 will definitely have 2.8 support (and when it's scheduled for)? Perhaps it's possible to just use Scala actors for the time being and switch to Akka at a later stage? Thanks, Dave

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• Composing actors

  - by Brian Heylin

  I've implemented a Listenable/Listener trait that can be added to Actors. I'm wondering if it's possible to attach this style of trait to an actor without it having to explicitly call the listenerHandler method? Also I was expecting to find this functionality in the Akka library. Am I missing something or is there some reason that Akka would not not include this? trait Listenable { this: Actor => private var listeners: List[Actor] = Nil protected def listenerHandler: PartialFunction[Any, Unit] = { case AddListener(who) => listeners = who :: listeners } protected def notifyListeners(event: Any) = { listeners.foreach(_.send(event)) } } class SomeActor extends Actor with Listenable { def receive = listenerHandler orElse { case Start => notifyListeners(Started()) case Stop => notifyListeners(Stopped()) } }

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• Open Grid Engine or Akka/Something more fault tolerant?

  - by Mike Lyons

  My use case is that I have a pipeline of independent, stand alone programs, that I want to execute in a certain order on specific pieces of data that our output from previous pipeline stages. The pipeline is entirely linear and doesn't do anything in terms of alternate paths through the pipe. I'm currently using SGE to do this and it works OK, however occasionally a job will overstep it's memory bounds, fail, and all jobs that require that output data will fail. The pipe needs to be restarted in that case, and it seems that whatever is providing the fault tolerance in akka might solve that for me?

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• Scala - Enumeration vs. Case-Classes

  - by tzofia

  I've created akka actor called LogActor. The LogActors's receive method handling messages from other actors and logging them to the specified log level. I can distinguish between the different levels in 2 ways. The first one: import LogLevel._ object LogLevel extends Enumeration { type LogLevel = Value val Error, Warning, Info, Debug = Value } case class LogMessage(level : LogLevel, msg : String) The second: (EDIT) abstract class LogMessage(msg : String) case class LogMessageError(msg : String) extends LogMessage(msg) case class LogMessageWarning(msg : String) extends LogMessage(msg) case class LogMessageInfo(msg : String) extends LogMessage(msg) case class LogMessageDebug(msg : String) extends LogMessage(msg) Which way is more efficient? does it take less time to match case class or to match enum value? (I read this question but there isn't any answer referring to the runtime issue)

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• Different Scala Actor Implementations Overview

  - by Stefan K.

  I'm trying to find the 'right' actor implementation for my thesis. I realized there is a bunch of them and it's a bit confusing to pick one. Personally I'm especially interested in remote actors, but I guess a complete overview would be helpful to many others. This is a pretty general question, so feel free to answer just for the implementation you know about. I know about the following Scala Actor implementations (SAI). Please add the missing ones. Scala 2.7 (difference to) Scala 2.8 Akka (http://www.akkasource.org/) Lift (http://liftweb.net/) Scalaz (http://code.google.com/p/scalaz/) What are the target use-cases for these SAIs (lightweight vs. "heavy" enterprise framework)? do they support remote actors? What shortcomings do remote actors have in the SAIs? How is their performace? How active is there community? How easy are they to get started? How good is the documentation? How easy are they to extend? How stable are they? Which projects are using them? What are their shortcomings? What are their design principles? Are they thread based or event based (receive/ react) or both? Nested receiveS hotswapping the Actor’s message loop

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• How do I rewrite a for loop with a shared dependency using actors

  - by Thomas Rynne

  We have some code which needs to run faster. Its already profiled so we would like to make use of multiple threads. Usually I would setup an in memory queue, and have a number of threads taking jobs of the queue and calculating the results. For the shared data I would use a ConcurrentHashMap or similar. I don't really want to go down that route again. From what I have read using actors will result in cleaner code and if I use akka migrating to more than 1 jvm should be easier. Is that true? However, I don't know how to think in actors so I am not sure where to start. To give a better idea of the problem here is some sample code: case class Trade(price:Double, volume:Int, stock:String) { def value(priceCalculator:PriceCalculator) = (priceCalculator.priceFor(stock)-> price)*volume } class PriceCalculator { def priceFor(stock:String) = { Thread.sleep(20)//a slow operation which can be cached 50.0 } } object ValueTrades { def valueAll(trades:List[Trade], priceCalculator:PriceCalculator):List[(Trade,Double)] = { trades.map { trade => (trade,trade.value(priceCalculator)) } } def main(args:Array[String]) { val trades = List( Trade(30.5, 10, "Foo"), Trade(30.5, 20, "Foo") //usually much longer ) val priceCalculator = new PriceCalculator val values = valueAll(trades, priceCalculator) } } I'd appreciate it if someone with experience using actors could suggest how this would map on to actors.

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• Resources relating to Java EE and Scala

  - by Ant Kutschera

  Are there any good sites / blogs / books / articles on using Java EE together with Scala? Or indeed articles saying that it should not be done. Many Scala resources talk about using Akka and Lift. Akka solves a different domain problem than Java EE. I don't know Lift, but I assume its geared towards the web end of Java EE and doesn't replace app server containers which provide transactions, security, scalability, resource management, reliability, etc. (all those things which Java EE markets itself as being good at).

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• Internet Troubles - PPPoE vs PPPoA?

  - by AkkA

  I have been having some internet troubles at home (ADSL2+ connection in Australia). We get random drop-outs from the authentication connection. It will keep the connection to the DSL service, but we lose authentication and either have to restart the router/modem (its combined, a Belkin one, not sure on model number) or unplug the phone cable, wait about 30 seconds and plug it in again. I've called the ISP (Telstra) a few times, but they only offer limited support when we dont use their supported hardware. Apparently something had happened on their side, they checked the box again (at least it sounded that simple), and told me it would be fine. It wasnt. I've replaced all the filters around the house, but that didnt help either. We do live a little bit away from the exchange (get a sync speed of about 3000/900), so I thought it could be due to line noise but that hasnt helped. Telstra allow both PPPoE and PPPoA connections (which I'm configuring through my router, dont have software on the PC side). I've been running PPPoA the whole time, would it make any difference changing it to PPPoE? If not, are there any other theories as to why we would be experiencing these drop-outs? It has been fine for at least 12 months, then suddenly started about 2 months ago.

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• Un-install network printer drivers from Win7 64 Home Premium

  - by AkkA

  I recently bought a NAS device that has print server functionality through USB. The printer was already installed and fully working on another Win XP box, set up that box to see the printer over the network and it prints fine. I tried to install the printer on my Win7 laptop (64 bit, Home Premium), but got the wrong drivers somehow, or it just refuses to work. I need to completely un-install the printer drivers and start from scratch. Removing the printer (by going to the printers folder, right click and remove) does not actually un-install the drivers. It only removes the printer from active use. Even if I try to re-install new drivers it will load the old ones. I have read a few things on the net that say to load up a device snap-in or something of the sort into Computer Management, but this seems to be valid for Win7 Pro or greater, the function everyone tells you to use isnt available in Home Premium. Is there anything I can use to manage device driver files in Home Premium? I want to completely remove them from the computer.

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• Internet Troubles - PPPoE vs PPPoA?

  - by AkkA

  I have been having some internet troubles at home (ADSL2+ connection in Australia). We get random drop-outs from the authentication connection. It will keep the connection to the DSL service, but we lose authentication and either have to restart the router/modem (its combined, a Belkin one, not sure on model number) or unplug the phone cable, wait about 30 seconds and plug it in again. I've called the ISP (Telstra) a few times, but they only offer limited support when we dont use their supported hardware. Apparently something had happened on their side, they checked the box again (at least it sounded that simple), and told me it would be fine. It wasnt. I've replaced all the filters around the house, but that didnt help either. We do live a little bit away from the exchange (get a sync speed of about 3000/900), so I thought it could be due to line noise but that hasnt helped. Telstra allow both PPPoE and PPPoA connections (which I'm configuring through my router, dont have software on the PC side). I've been running PPPoA the whole time, would it make any difference changing it to PPPoE? If not, are there any other theories as to why we would be experiencing these drop-outs? It has been fine for at least 12 months, then suddenly started about 2 months ago.

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• Performance of concurrent software on multicore processors

  - by Giorgio

  Recently I have often read that, since the trend is to build processors with multiple cores, it will be increasingly important to have programming languages that support concurrent programming in order to better exploit the parallelism offered by these processors. In this respect, certain programming paradigms or models are considered well-suited for writing robust concurrent software: Functional programming languages, e.g. Haskell, Scala, etc. The actor model: Erlang, but also available for Scala / Java (Akka), C++ (Theron, Casablanca, ...), and other programming languages. My questions: What is the state of the art regarding the development of concurrent applications (e.g. using multi-threading) using the above languages / models? Is this area still being explored or are there well-established practices already? Will it be more complex to program applications with a higher level of concurrency, or is it just a matter of learning new paradigms and practices? How does the performance of highly concurrent software compare to the performance of more traditional software when executed on multiple core processors? For example, has anyone implemented a desktop application using C++ / Theron, or Java / Akka? Was there a boost in performance on a multiple core processor due to higher parallelism?

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• Do you think Scala will be the dominant JVM langauge, ie be the next Java? [on hold]

  - by user1037729

  From what I've read about Scala do far I think it has some nice features but I do not think it should be "the next Java". It might however end up being the next Java (due to fashion rather than fact) but lets not hope it does not... To me adds a lot of complexity over Java which is a simple and scalable language. Scala Pattern matching allows you to perform some type/value checking in a more concise way, this is possible in Java, Scala's pattern matching has a limit to it, you cannot continuously match deeper and deeper down the object graph, so why not just stick to Java and use decent invariants? Scala provides tuples, easy enough to make in Java, create a static factory method and it all reads nicely too. Scala provides mixins, why not just use composition? I believe Scala implicit's are bad, they can lead to code becoming complex and hard to maintain, explicitness is good. Scala provides closures, well they will be in Java 8 too. Scala has lazy keyword for lazy instantiation, this is easy enough to do in Java by calling a getter which creates the instance when needed, no hidden magic here. Scala can be used with AKKA, well so can Java, there is an Java AKKA implementation. Scala offers addition functional features but these can all be created in Java, there are many frameworks with have implemented functional features in Java. All in all Scala seems to offer is addition complexity and thats it...

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• 5 New Java Champions

  - by Tori Wieldt

  The Java Champions have nominated and accepted five new members to their group: Jonas Bonér, James Strachan, Rickard Oberg, Régina ten Bruggencate, and Clara Ko. Congratulations, and we look forward to hearing more from each of them!Jonas Bonér (Sweden) is a Java entrepreneur, programmer, teacher, speaker and author. He is an active contributor to the Open Source community; and most notably created the Akka Project, AspectWerkz Aspect-Oriented Programming (AOP) framework. James Strachan (UK) has more than 20 years experience in enterprise software development with a background in finance and middleware and is also committer on a number of open source projects, including Apache Karaf, Maven, Lift and Jersey.Rickard Oberg (Malaysia) has worked on several Open Source projects that involve JEE development, such as JBoss, XDoclet and WebWork. He has also been the principal architect of the SiteVision CMS/portal platform, where he used AOP as the foundation. Now he works for Jayway, developing the Qi4j framework and Composite Oriented Programming paradigm.Régina ten Bruggencate (Netherlands) is a senior Java developer for iProfs with 10-plus years of Java experience, mainly on enterprise applications. Régina is the current president of Duchess, and as such has the responsibility for the site and community. Duchess is a global organization for women in Java technology, currently with 350 members in over 50 countries.Clara Ko (Netherlands) is a freelance Java/J2EE professional living in Amsterdam. She has worked as a developer, architect, and project manager. She promotes the use of open source software and has led initiatives to adopt agile practices across multiple organizations. Clara is also co-founder of Duchess.The Java Champions are an exclusive group of passionate Java technology and community leaders who are community-nominated and selected under a project sponsored by Oracle. Java Champions get the opportunity to provide feedback, ideas, and direction that will help Oracle grow the Java Platform. This interchange may be in the form of technical discussions and/or community-building activities with Oracle's Java Development and Developer Program teams. Full bios and details about the champions are on http://java-champions.java.net/.

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• Java - System design with distributed Queues and Locks

  - by sunny

  Looking for inputs to evaluate a design for a system (java) which would have a distributed queue serving several (but not too many) nodes. These nodes would process objects present in the distributed queue and on occasion require a distributed lock across the cluster on an arbitrary (distributed) data structures. These (distributed) data structures could potentially lie in a distributed cache. Eliminating Terracotta (DSO),Hazelcast and Akka what could be alternative choices. Currently considering zookeeper as a distributed locking mechanism. Since the recommendation of a znode is not to exceed the 1M size , the understanding is that zookeeper should not be used a distributed queue. And also from Netflix curator tech note 4. So should a distributed cache, say like memcached, or redis be used to emulate a distributed queue ? i.e. The distributed queue will be stored in the caches and will be locked cluster-wide via zookeeper. Are there potential pitfalls with this high-level approach. The objects don't need to be taken off the queue. The object will pass through a lifecycle which will determine its removal from the queue. There would be about 10k+ objects in a queue at a given time changing states and any node could service one stage of the object's lifecycle. (Although not strictly necessary .. i.e. one node could serve the entire lifecycle if that is more efficient.) Any suggestions/alternatives ? sidenote: new to zookeeper ; redis etc.

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• rsyslog - regex trouble

  - by benmccann

  I'm trying to setup the logentries service. If a log entry has a token in it then I would like to send it to api.logentries.com:10000. The token is a guid in the format aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee. Right now I'm doing: # If there's a logentries token then send it directly to logentries :msg, regex, ".*[a-z0-9]{8}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{12}.*" & @@api.logentries.com:10000 I checked the rsyslog debug logs and my regex is not matching, but I can't figure out why or how to fix it: 5245.961161378:7fb79b514700: Filter: check for property 'msg' (value ' fb1c507f-2ede-4d7f-a140-2bd8d56e133 - application - [play-akka.actor.default-dispatcher-1] - Found user: 4fb11ea5e4b00a1aeebe2800') regex '.*[a-z0-9]{8}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{12}.*': FALSE

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• Sweden: Hot Java in the Winter

  - by Tori Wieldt

  No, it's not global warming, but for some reason Sweden is a hotbed of great Java developers and great Java conferences in the winter. First, all three Swedish Java Champions are on Computer Sweden's 100 Best Swedish Developers List. You can read the full Sweden's Top 100 Developers article *if* you can read Swedish (or want to use Google Translate). Congratulations to:  Jonas Bonér, CTO Typesafe Skills: In recent years worked with solutions for scalability and availability. Previously, most between programs and compilers. Other qualifications: Located behind the framework Aspectwerkz and Akka platform for developing parallel, scalable and fault-tolerant software in Scala and Java. Rickard Oberg, Neo Technology Skills: Java, and the framework in Java EE and graph databases. Other qualifications: Founder of open source projects Xdoclet and Webwork. The latter is now called Struts second Rickard Oberg wrote the basics of the application server JBoss. Founder of Senselogic and architect of CMS and portal product SiteVision. Launched frameworkQi4j. Been a speaker at Java Zone JavaPolis, Jfokus, Øredev. Mattias Karlsson Skills: Java. Good at agile system development methods and architecture. Activity: telecom, banking, finance and insurance. Other qualifications: Runs Javaforum Stockholm. Arranges the conference Jfokus.  Frequent speaker at major international conferences such as JavaOne. Holds the title Java Champion. Also, Sweden is home to some top-notch Java Developer conferences during the Winter: jDays Gothenburg, Sweden, Dec 3-5. jDays, a dynamic Java developer conference, comes to Gothenburg. In addition to conference and presentations, visitors can join any courses in Java and related technologies for free.  Jfokus Stockholm, Sweden, Feb 4-6. Jfokus is the largest annual conference for everyone who works with Java in Sweden. The conference is arranged together with Javaforum, the Stockholm JUG.  Thanks to all the Java community who keep the Java hot in Sweden!

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• How does Play recognize a particular websocket message?

  - by noncom

  I am looking at the websocket-chat example. It unveils much, but I still cannot get something. I understand how messages are received, processed and sent on the web page side. However, Play captures websocket messages by means of the receive method of an Akka actor. In the websocket-chat, there are several cases in this method, but I don't get, how does it know which websocket message should be mapped to which case. In fact, I don't understand the path that a websocket message follows upon entering Play's domain, how is it processed and how can different message types/kinds be sent from the webpage. I have not find any info or sources related to this. Could please someone explain this or point to some kind of a good reference? UPDATE: The link to the original example.

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• Diving into Scala with Cay Horstmann

  - by Janice J. Heiss

  A new interview with Java Champion Cay Horstmann, now up on otn/java, titled  "Diving into Scala: A Conversation with Java Champion Cay Horstmann," explores Horstmann's ideas about Scala as reflected in his much lauded new book,  Scala for the Impatient.  None other than Martin Odersky, the inventor of Scala, called it "a joy to read" and the "best introduction to Scala". Odersky was so enthused by the book that he asked Horstmann if the first section could be made available as a free download on the Typesafe Website, something Horstmann graciously assented to. Horstmann acknowledges that some aspects of Scala are very complex, but he encourages developers to simply stay away from those parts of the language. He points to several ways Java developers can benefit from Scala: "For example," he says, " you can write classes with less boilerplate, file and XML handling is more concise, and you can replace tedious loops over collections with more elegant constructs. Typically, programmers at this level report that they write about half the number of lines of code in Scala that they would in Java, and that's nothing to sneeze at. Another entry point can be if you want to use a Scala-based framework such as Akka or Play; you can use these with Java, but the Scala API is more enjoyable. " Horstmann observes that developers can do fine with Scala without grasping the theory behind it. He argues that most of us learn best through examples and not through trying to comprehend abstract theories. He also believes that Scala is the most attractive choice for developers who want to move beyond Java and C++.  When asked about other choices, he comments: "Clojure is pretty nice, but I found its Lisp syntax a bit off-putting, and it seems very focused on software transactional memory, which isn't all that useful to me. And it's not statically typed. I wanted to like Groovy, but it really bothers me that the semantics seems under-defined and in flux. And it's not statically typed. Yes, there is Groovy++, but that's in even sketchier shape. There are a couple of contenders such as Kotlin and Ceylon, but so far they aren't real. So, if you want to do work with a statically typed language on the JVM that exists today, Scala is simply the pragmatic choice. It's a good thing that it's such a nice choice." Learn more about Scala by going to the interview here.

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• Are there any good Java/JVM libraries for my Expression Tree architecture?

  - by Snuggy

  My team and I are developing an enterprise-level application and I have devised an architecture for it that's best described as an "Expression Tree". The basic idea is that the leaf nodes of the tree are very simple expressions (perhaps simple values or strings). Nodes closer to the trunk will get more and more complex, taking the simpler nodes as their inputs and returning more complex results for their parents. Looking at it the other way, the application performs some task, and for this it creates a root expression. The root expression divides its input into smaller units and creates child expressions, which when evaluated it can use to build it's own result. The subdividing process continues until the simplest leaf nodes. There are two very important aspects of this architecture: It must be possible to manipulate nodes of the tree after it is built. The nodes may be given new input values to work with and any change in result for that node needs to be propagated back up the tree to the root node. The application must make best use of available processors and ultimately be scalable to other computers in a grid or in the cloud. Nodes in the tree will often be updating concurrently and notifying other interested nodes in the tree when they get a new value. Unfortunately, I'm not at liberty to discuss my actual application, but to aid understanding a little bit, you might imagine a kind of spreadsheet application being implemented with a similar architecture, where changes to cells in the table are propagated all over the place to other cells that need the result. The spreadsheet could get so massive that applying multi-core multi-computer distributed system to solve it would be of benefit. I've got my prototype "Expression Engine" working nicely on a single multi-core PC but I've started to run into a few concurrency issues (as expected because I haven't been taking too much care so far) so it's now time to start thinking about migrating the Engine to a more robust library, and that leads to a number of related questions: Is there any precedent for my "Expression Tree" architecture that I could research? What programming concepts should I consider. I realise this approach has many similarities to a functional programming style, and I'm already aware of the concepts of using futures and actors. Are there any others? Are there any languages or libraries that I should study? This question is inspired by my accidental discovery of Scala and the Akka library (which has good support for Actors, Futures, Distributed workloads etc.) and I'm wondering if there is anything else I should be looking at as well?

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• top tweets WebLogic Partner Community – March 2012

  - by JuergenKress

  Send us your tweets @wlscommunity #WebLogicCommunity and follow us on twitter http://twitter.com/wlscommunity PeterPaul ? RT @JDeveloper: EJB 3 Deployment guide for WebLogic Server Version: 10.3.4.0 dlvr.it/1J5VcV Andrejus Baranovskis ?Open ADF PopUp on Page Load fb.me/1Rx9LP3oW Sten Vesterli ? RT @OracleBlogs: Using the Oracle E-Business Suite SDK for Java on ADF Applications ow.ly/1hVKbB <- Neat! No more WS calls Java Buddy ?JavaFX 2.0: Example of MediaPlay java-buddy.blogspot.com/2012/03/javafx… Georges Saab Build improvements coming to #openJDK for #jdk8 mail.openjdk.java.net/pipermail/buil… NetBeans Team Share your #Java experience! JavaOne 2012 India call for papers: ow.ly/9xYg0 GlassFish ? GlassFish 3.1.2 Screencasts & Videos – bit.ly/zmQjn2 chriscmuir ?G+: New blog post: ADF Runtimes vs WLS versions as of JDeveloper 11.1.1.6.0 – bit.ly/y8tkgJ Michael Heinrichs New article: Creating a Sprite Animation with JavaFX blog.netopyr.com/2012/03/09/cre… Oracle WebLogic ? #WebLogic Devcast Webinar Series for March: Enterprise Java Scale Out, JPA, Distributed Grid Data Cache bit.ly/zeUXEV #Coherence Andrejus Baranovskis ?Extending Application Module for ADF BC Proxy User DB Connection fb.me/Bj1hLUqm OTNArchBeat ? Oracle Fusion Middleware on JDK 7 | Mark Nelson bit.ly/w7IroZ OTNArchBeat ? Java Champion Jonas Bonér Explains the Akka Platform bit.ly/x2GbXm Adam Bien ? (Java) FX Experience Tools–Feels Like Native Mac App: FX Experience Tools application comes with a native Mac O… bit.ly/waHF3H GlassFish ? GlassFish new recruit and Eclipse integration progress – bit.ly/y5eEkk JDeveloper & ADF Prototyping ADF Libraries dlvr.it/1Hhnw0 Eric Elzinga ?Oracle Fusion Middleware on JDK 7, bit.ly/xkphFQ ADF EMG ? Working with ADF in Arabic, Hebrew or other right-to-left-written language? Oracle UX asks for your help. groups.google.com/forum/?fromgro… Java ? A simple #JavaFX Login Form with a TRON like effect ow.ly/9n9AG JDeveloper & ADF ? Logging in Oracle ADF Applications dlvr.it/1HZhcX OTNArchBeat ? Oracle Cloud Conference: dates and locations worldwide bit.ly/ywXydR UK Oracle User Group ? Simon Haslam, ACE Director present on #WebLogic for DBAs at #oug_ire2012 j.mp/zG6vz3 @oraclewebcenter @oracleace #dublin Steven Davelaar ? Working with ADF and not a member of ADF EMG? You miss lots of valuable info, join now! sites.google.com/site/oracleemg… Simon Haslam @MaciejGruszka: Oracle plans to provide Forms & Reports plug-in for OVAB next year to help deployment. #ukoug MW SIG GlassFish ? Introducing JSR 357: Social Media API – bit.ly/yC8vez JAX London ? Are you coming to Java EE workshops by @AdamBien at JAX Days? Save £100 by registering today. #jaxdays #javaee jaxdays.com WebLogic Community ?Welcome to our Munich WebLogic 12c Bootcamp in Munich! If you also want to attend a training register for the Community oracle.com/partners/goto/… chriscmuir ? My first webcast for Oracle! (be kind) Basing ADF Business Component View Objects on More that one Entity Object bit.ly/ArKija OTNArchBeat ? Oracle Weblogic Server 12c is available on Oracle Solaris 11 (SPARC and x86) bit.ly/xE3TLg JDeveloper & ADF ? Basing ADF Business Component View Objects on More that one Entity Object – YouTube dlvr.it/1H93Qr OTNArchBeat ? Application-Driven Virtualization with Oracle Virtual Assembly Builder | Ronen Kofman bit.ly/wF1C1N Oracle WebLogic ? Steve Button’s blog: WebLogic Server Singleton Services ow.ly/1hOu4U Barbara Ann May ?@oracledevtools: New update: #NetBeans IDE 7.1.1, with support for #GlassFish 3.1.2 bit.ly/mOLcQd #java #developer OTNArchBeat ? Using Coherence with JDeveloper: bit.ly/AkoEQb WebLogic Community ? WebLogic Partner Community Newsletter February 2012 wp.me/p1LMIb-f3 GlassFish ? GlassFish 3.1.2 – new Podcast episode : bit.ly/wc6oBE Frank Nimphius ?Cool! Open JDeveloper 11.1.1.5, go help–>check for updates. First thing shown is that 11.1.1.6 is available. Never miss a new release Adam Bien ?5 Minutes (Video) With Java EE …Or With NetBeans + GlassFish: This screencast covers a 5-minute development of a… bit.ly/xkOJMf WebLogic Community ? Free Oracle WebLogic Certification Application Grid Implementation Specialist wp.me/p1LMIb-eT OTNArchBeat ?Oracle Coherence: First Steps Using Clusters and Basic API Usage | Ricardo Ferreira bit.ly/yYQ3Wz GlassFish ? JMS 2.0 Early Draft is here – bit.ly/ygT1VN OTNArchBeat ? Exalogic Networking Part 2 | The Old Toxophilist bit.ly/xuYMIi OTNArchBeat ?New Release: GlassFish Server 3.1.2. Read All About It! | Paul Davies bit.ly/AtlGxo Oracle WebLogic ?OTN Virtual Developer Day: #WebLogic 12c & #Coherence ost-conference on-demand page live with bonus #Virtualbox lab – bit.ly/xUy6BJ Oracle WebLogic ? Steve Button’s blog: WebLogic Server 11g (10.3.6) Documentation ow.ly/1hJgUB Lucas Jellema ? Just published an article on the AMIS blog: technology.amis.nl/2012/03/adf-11… ADF 11g – programmatically sorting rich table columns. Java Certification ? New Course! Learn how to create mobile applications using Java ME: bit.ly/xZj1Jh Simon Haslam ? @MaciejGruszka WebLogic 12c can run against 11g domain config without changes …and can rollback to 11. #ukoug MW SIG Justin Kestelyn ? Learn Advanced ADF, free and online bit.ly/wEKSRc WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: twitter,WebLogic,WebLogic Community,OPN,Oracle,Jürgen Kress,WebLogic 12c

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