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  • deploying gwt web application on jetty

    - by Azhar
    Hi I am deploying my web application created in Gwt on the jetty. I have used mongodb as my database.After starting the server it starts deploying the weapp.war and gives following error - 694 [main] INFO org.mortbay.log - Extract /usr/share/jetty/webapps/myapp.war to /tmp/Jetty_0_0_0_0_8090_myapp.war__myapp__n6yltk/webapp 3567 [main] WARN org.mortbay.log - failed Startup: java.lang.LinkageError: loader constraint violation: loader (instance of org/mortbay/jetty/webapp/WebAppClassLoader) previously initiated loading for a different type with name "javax/management/MBeanServer" at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:634) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:277) at java.net.URLClassLoader.access$000(URLClassLoader.java:73) at java.net.URLClassLoader$1.run(URLClassLoader.java:212) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:392) at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:363) at com.mongodb.DBPortPool$Holder.get(DBPortPool.java:58) at com.mongodb.DBTCPConnector._set(DBTCPConnector.java:458) at com.mongodb.DBTCPConnector.<init>(DBTCPConnector.java:46) at com.mongodb.Mongo.<init>(Mongo.java:137) at com.mongodb.Mongo.<init>(Mongo.java:123)

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  • By-Name-Parameters for Constructors

    - by hotzen
    Hello, coming from my other question is there a way to get by-name-parameters for constructors working? I need a way to provide a code-block which is executed on-demand/lazy/by-name inside an object and this code-block must be able to access the class-methods as if the code-block were part of the class. Following Testcase fails: package test class ByNameCons(code: => Unit) { def exec() = { println("pre-code") code println("post-code") } def meth() = println("method") def exec2(code2: => Unit) = { println("pre-code") code2 println("post-code") } } object ByNameCons { def main(args: Array[String]): Unit = { val tst = new ByNameCons { println("foo") meth() // knows meth() as code is part of ByNameCons } tst.exec() // ByName fails (executed right as constructor) println("--------") tst.exec2 { // ByName works println("foo") //meth() // does not know meth() as code is NOT part of ByNameCons } } } Output: foo method pre-code post-code -------- pre-code foo post-code

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  • Testing SocketChannel NIO

    - by hotzen
    Hello, I just wrote some NIO-code and wonder how to stress-test my implementation regarding SocketChannel.write(ByteBuffer) not able to write the whole byte-buffer SocketChannel.read(ByteBuffer) reading the data in chunks into ByteBuffer are there some simple linux-utilities like telnet to open a ServerSocket with some buffering-options?

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  • How do I get the scalaz IDEA live templates working for the symbolic methods?

    - by oxbow_lakes
    Many of the methods in scalaz have symbolic equivalents, such as forever and 8 (of course, I have this the wrong way round, the symbolic methods really have ASCII equivalents). The project contains a live templates XML file for IDEA so these can be auto-completed, I believe by using the forever+TAB shortcut (in the above instance). I can't figure out how to import this live template into IDEA and actually use it, though. How can I do that?

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  • Estimate serialization size of objects?

    - by Stefan K.
    In my thesis, I woud like to enhance messaging in a cluster. It's important to log runtime information about how big a message is (should I prefer processing local or remote). I could just find frameoworks about estimating the object memory size based on java instrumentation. I've tested classmexer, which didn't come close to the serialization size and sourceforge SizeOf. In a small testcase, SizeOf was around 10% wrong and 10x faster than serialization. (Still transient breaks the estimation completely and since e.g. ArrayList is transient but is serialized as an Array, it's not easy to patch SizeOf. But I could live with that) On the other hand, 10x faster with 10% error doesn't seem very good. Any ideas how I could do better?

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  • Lift XML Parsing Error

    - by bstevens90
    I know there are other questions on this and I have read through almost all of them and none of them solved my problem. I have inside a home directory: def search(in: NodeSeq) : NodeSeq = { bind("work", in, "docId" -> text("", did = _), "visitId" -> text("", vid = _), "provider" -> text("", prov = _), "emCode" -> text(ecode, ecode = _)) } along with: <lift:home.searchForm form="POST" multipart="true" > <table> <tr> <td>DocId</td> <td>VisitId</td> <td>Provider</td> <td>EanMCode</td> </tr> <tr> <td><work:docId /></td> <td><work:visitId /></td> <td><work:provider /></td> <td><work:emCode /></td> <td><button>Click Me!</button></td> </tr> </table> </lift:home.searchForm> Inside an html page. I have included xmlns:lift="http://liftweb.net/" in default.... I can't find anyway to fix this... I am getting XML Parsing Error: prefix not bound to a namespace Location: http://localhost:8080/ Line Number 29, Column 10: <td><work:docId></work:docId></td> in firefox. I have written similar code and had it working in another app and just cant even find anything im doing different thats not trivial naming... Thanks in advance!

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  • trait implementation

    - by Jeriho
    If I have some traits like: trait A {...} trait B extends A{...} trait C1 extends B{...} trait C2 extends A{...} I can write class in two ways (C1 and C2 add same functionality) class Concrete1 extends B with C1 class Concrete2 extends B with C2 What variant is better(efficient)?

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  • implicit parameter definition in class

    - by coubeatczech
    implicit val odkaz = head; def vypis(implicit odkaz:Prvek):String = { odkaz match{ case null => "" case e => e.cislo + " " + e.pocet + "\n" + vypis(e.dalsi) } } ... def main(args:Array[String]){ val q = new MyQueue() // insert some values println(q.vypis) } This method(vypis) is a member of an queue-class so I'll always want to implicity start the recursion from the start of the queue, when calling the method from outside. Is there a way how to write it, that the method from outside calling, there's no paramter, but in inside, there's a parameter - for recursion...? The compiler complains that the parameter is not defined when called from outside

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  • Usage of @specialized in traits

    - by paradigmatic
    I have a trait and an implementation looking like: trait Foo[A] { def bar[B >: A: Ordering]: Foo[B] } class FooImpl[A]( val a: A, val values: List[Foo[A]] ) extends Foo[A] { def bar[B >: A] = { /* concrete implementation */} } I would like to use the @specialized annotation on A and B to avoid autoboxing. Do I need to use it in both trait and implementation, only in implementation, or only in trait ?

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  • How to compose a Matcher[Iterable[A]] from a Matcher[A] with specs testing framework

    - by Garrett Rowe
    If I have a Matcher[A] how do create a Matcher[Iterable[A]] that is satisfied only if each element of the Iterable satisfies the original Matcher. class ExampleSpec extends Specification { def allSatisfy[A](m: => Matcher[A]): Matcher[Iterable[A]] = error("TODO") def notAllSatisfy[A](m: => Matcher[A]): Matcher[Iterable[A]] = allSatisfy(m).not "allSatisfy" should { "Pass if all elements satisfy the expectation" in { List(1, 2, 3, 4) must allSatisfy(beLessThan(5)) } "Fail if any elements do not satisfy the expectation" in { List(1, 2, 3, 5) must notAllSatisfy(beLessThan(5)) } } }

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  • Concatenating databases with Squeryl

    - by Pengin
    I'm trying to use Squeryl to take the contents of a table from one database, and append it to the equivalent table in another database. The primary key will have to be reassigned in the process, but I'm getting the error NULL not allowed for column "SIMID". Why is this? object Concatenator { def main(args: Array[String]) { Class.forName("org.h2.Driver"); val seshA = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsA", "sa", "password"), new H2Adapter ) val seshB = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsB", "sa", "password"), new H2Adapter ) using(seshA){ import Library._ from(sims){s => select(s)}.foreach{item => using(seshB){ sims.insert(item); } } } } case class Simulation( @Column("SIMID") var id: Long, val date: Date ) extends KeyedEntity[Long] object Library extends Schema { val sims = table[Simulation] on(sims)(s => declare( s.id is(unique, indexed, autoIncremented) )) } }

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  • Parsing a dynamic value with Lift-JSON

    - by Surya Suravarapu
    Let me explain this question with an example. If I have a JSON like the following: {"person1":{"name": "Name One", "address": {"street": "Some Street","city": "Some City"}}, "person2":{"name": "Name Two", "address": {"street": "Some Other Street","city": "Some Other City"}}} [There is no restriction on the number of persons, the input JSON can have many more persons] I could extract this JSON to Persons object by doing var persons = parse(res).extract[T] Here are the related case classes: case class Address(street: String, city: String) case class Person(name: String, address: Address, children: List[Child]) case class Persons(person1: Person, person2: Person) Question: The above scenario works perfectly fine. However the need is that the keys are dynamic in the key/value pairs. So in the example JSON provided, person1 and person2 could be anything, I need to read them dynamically. What's the best possible structure for Persons class to account for that dynamic nature.

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  • how to define a structural type that refers to itself?

    - by IttayD
    I want to create a method sum that I can call on different types, specifically sum(1,2). def sum[A](a1: A, a2: A) = a1 + a2 This fails because the compiler can't tell if A has a method '+' I tried to define a structural type: type Addable = {def +(a: Addable)} This fails because of an illegal cyclic reference How can I achieve this in a type safe way without requiring A to extend a specific trait?

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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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  • Parsing HTTP - Bytes.length != String.length

    - by hotzen
    Hello, I consume HTTP via nio.SocketChannel, so I get chunks of data as Array[Byte]. I want to put these chunks into a parser and continue parsing after each chunk has been put. HTTP itself seems to use an ISO8859-Charset but the Payload/Body itself may be arbitrarily encoded: If the HTTP Content-Length specifies X bytes, the UTF8-decoded Body may have much less Characters (1 Character may be represented in UTF8 by 2 bytes, etc). So what is a good parsing strategy to honor an explicitly specified Content-Length and/or a Transfer-Encoding: Chunked which specifies a chunk-length to be honored. append each data-chunk to an mutable.ArrayBuffer[Byte], search for CRLF in the bytes, decode everything from 0 until CRLF to String and match with Regular-Expressions like StatusRegex, HeaderRegex, etc? decode each data-chunk with the proper charset (e.g. iso8859, utf8, etc) and add to StringBuilder. With this solution I am not able to honor any Content-Length or Chunk-Size, but.. do I have to care for it? any other solution... ?

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  • An Actor "queue" ?

    - by synic
    In Java, to write a library that makes requests to a server, I usually implement some sort of dispatcher (not unlike the one found here in the Twitter4J library: http://github.com/yusuke/twitter4j/blob/master/twitter4j-core/src/main/java/twitter4j/internal/async/DispatcherImpl.java) to limit the number of connections, to perform asynchronous tasks, etc. The idea is that N number of threads are created. A "Task" is queued and all threads are notified, and one of the threads, when it's ready, will pop an item from the queue, do the work, and then return to a waiting state. If all the threads are busy working on a Task, then the Task is just queued, and the next available thread will take it. This keeps the max number of connections to N, and allows at most N Tasks to be operating at the same time. I'm wondering what kind of system I can create with Actors that will accomplish the same thing? Is there a way to have N number of Actors, and when a new message is ready, pass it off to an Actor to handle it - and if all Actors are busy, just queue the message?

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  • Straight Java/Groovy versus ETL tool (Talend/etc) - what libraries would you use?

    - by Alex R
    Assume you have a small project which on the surface looks like a good match for an ETL tool like Talend. But assume further, that you have never used Talend and furthermore, you do not trust "visual programming" tools in general and would rather code everything the old fashioned way (text on a nice IDE!) with the help of an appropriate language & support libraries. What are some language patterns & support libraries that could help you stay away from the ETL tool temptation/trap?

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  • Higher-kinded Types with C++

    - by Venkat Shiva
    This question is for the people who know both Haskell (or any other functional language that supports Higher-kinded Types) and C++... Is it possible to model higher kinded types using C++ templates? If yes, then how?

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