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• Spring <jee:remote-slsb> and JBoss AS7 - No EJB receiver available for handling

  - by Lech Glowiak

  I have got @Remote EJB on JBoss AS 7, available by name java:global/RandomEjb/DefaultRemoteRandom!pl.lechglowiak.ejbTest.RemoteRandom. Standalone client is Spring application that uses <jee:remote-slsb> bean. When trying to use that bean I get java.lang.IllegalStateException: EJBCLIENT000025: No EJB receiver available for handling [appName:, moduleName:RandomEjb, distinctName:] combination for invocation context org.jboss.ejb.client.EJBClientInvocationContext@1a89031. Here is relevant part of applicationContext.xml: <jee:remote-slsb id="remoteRandom" jndi-name="RandomEjb/DefaultRemoteRandom!pl.lechglowiak.ejbTest.RemoteRandom" business-interface="pl.lechglowiak.ejbTest.RemoteRandom" <jee:environment> java.naming.factory.initial=org.jboss.naming.remote.client.InitialContextFactory java.naming.provider.url=remote://localhost:4447 jboss.naming.client.ejb.context=true java.naming.security.principal=testuser java.naming.security.credentials=testpassword </jee:environment> </jee:remote-slsb> <bean id="remoteClient" class="pl.lechglowiak.RemoteClient"> <property name="remote" ref="remoteRandom" /> </bean> RemoteClient.java public class RemoteClient { private RemoteRandom random; public void setRemote(RemoteRandom random){ this.random = random; } public Integer callRandom(){ try { return random.getRandom(100); } catch (Exception e) { e.printStackTrace(); return null; } } } My jboss client jar: org.jboss.as jboss-as-ejb-client-bom 7.1.2.Final pom pl.lechglowiak.ejbTest.RemoteRandom is available for client application classpath. jndi.properties contains exact properties as in <jee:environment> of <jee:remote-slsb>. Such code runs without exception: Context ctx2 = new InitialContext(); RemoteRandom rr = (RemoteRandom) ctx2.lookup("RandomEjb/DefaultRemoteRandom!pl.lechglowiak.ejbTest.RemoteRandom"); System.out.println(rr.getRandom(10000)); But this: ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml"); RemoteClient client = ctx.getBean("remoteClient", RemoteClient.class); System.out.println(client.callRandom()); ends with exception: java.lang.IllegalStateException: EJBCLIENT000025: No EJB receiver available for handling [appName:, moduleName:RandomEjb, distinctName:] combination for invocation context org.jboss.ejb.client.EJBClientInvocationContext@1a89031. jboss.naming.client.ejb.context=true is set. Do you have any idea what am I setting wrong in <jee:remote-slsb>?

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• Fixed point math in c#?

  - by x4000

  Hi there, I was wondering if anyone here knows of any good resources for fixed point math in c#? I've seen things like this (http://2ddev.72dpiarmy.com/viewtopic.php?id=156) and this (http://stackoverflow.com/questions/79677/whats-the-best-way-to-do-fixed-point-math), and a number of discussions about whether decimal is really fixed point or actually floating point (update: responders have confirmed that it's definitely floating point), but I haven't seen a solid C# library for things like calculating cosine and sine. My needs are simple -- I need the basic operators, plus cosine, sine, arctan2, PI... I think that's about it. Maybe sqrt. I'm programming a 2D RTS game, which I have largely working, but the unit movement when using floating-point math (doubles) has very small inaccuracies over time (10-30 minutes) across multiple machines, leading to desyncs. This is presently only between a 32 bit OS and a 64 bit OS, all the 32 bit machines seem to stay in sync without issue, which is what makes me think this is a floating point issue. I was aware from this as a possible issue from the outset, and so have limited my use of non-integer position math as much as possible, but for smooth diagonal movement at varying speeds I'm calculating the angle between points in radians, then getting the x and y components of movement with sin and cos. That's the main issue. I'm also doing some calculations for line segment intersections, line-circle intersections, circle-rect intersections, etc, that also probably need to move from floating-point to fixed-point to avoid cross-machine issues. If there's something open source in Java or VB or another comparable language, I could probably convert the code for my uses. The main priority for me is accuracy, although I'd like as little speed loss over present performance as possible. This whole fixed point math thing is very new to me, and I'm surprised by how little practical information on it there is on google -- most stuff seems to be either theory or dense C++ header files. Anything you could do to point me in the right direction is much appreciated; if I can get this working, I plan to open-source the math functions I put together so that there will be a resource for other C# programmers out there. UPDATE: I could definitely make a cosine/sine lookup table work for my purposes, but I don't think that would work for arctan2, since I'd need to generate a table with about 64,000x64,000 entries (yikes). If you know any programmatic explanations of efficient ways to calculate things like arctan2, that would be awesome. My math background is all right, but the advanced formulas and traditional math notation are very difficult for me to translate into code.

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• TcpListener is queuing connections faster than I can clear them

  - by Matthew Brindley

  As I understand it, TcpListener will queue connections once you call Start(). Each time you call AcceptTcpClient (or BeginAcceptTcpClient), it will dequeue one item from the queue. If we load test our TcpListener app by sending 1,000 connections to it at once, the queue builds far faster than we can clear it, leading (eventually) to timeouts from the client because it didn't get a response because its connection was still in the queue. However, the server doesn't appear to be under much pressure, our app isn't consuming much CPU time and the other monitored resources on the machine aren't breaking a sweat. It feels like we're not running efficiently enough right now. We're calling BeginAcceptTcpListener and then immediately handing over to a ThreadPool thread to actually do the work, then calling BeginAcceptTcpClient again. The work involved doesn't seem to put any pressure on the machine, it's basically just a 3 second sleep followed by a dictionary lookup and then a 100 byte write to the TcpClient's stream. Here's the TcpListener code we're using: // Thread signal. private static ManualResetEvent tcpClientConnected = new ManualResetEvent(false); public void DoBeginAcceptTcpClient(TcpListener listener) { // Set the event to nonsignaled state. tcpClientConnected.Reset(); listener.BeginAcceptTcpClient( new AsyncCallback(DoAcceptTcpClientCallback), listener); // Wait for signal tcpClientConnected.WaitOne(); } public void DoAcceptTcpClientCallback(IAsyncResult ar) { // Get the listener that handles the client request, and the TcpClient TcpListener listener = (TcpListener)ar.AsyncState; TcpClient client = listener.EndAcceptTcpClient(ar); if (inProduction) ThreadPool.QueueUserWorkItem(state => HandleTcpRequest(client, serverCertificate)); // With SSL else ThreadPool.QueueUserWorkItem(state => HandleTcpRequest(client)); // Without SSL // Signal the calling thread to continue. tcpClientConnected.Set(); } public void Start() { currentHandledRequests = 0; tcpListener = new TcpListener(IPAddress.Any, 10000); try { tcpListener.Start(); while (true) DoBeginAcceptTcpClient(tcpListener); } catch (SocketException) { // The TcpListener is shutting down, exit gracefully CheckBuffer(); return; } } I'm assuming the answer will be related to using Sockets instead of TcpListener, or at least using TcpListener.AcceptSocket, but I wondered how we'd go about doing that? One idea we had was to call AcceptTcpClient and immediately Enqueue the TcpClient into one of multiple Queue<TcpClient> objects. That way, we could poll those queues on separate threads (one queue per thread), without running into monitors that might block the thread while waiting for other Dequeue operations. Each queue thread could then use ThreadPool.QueueUserWorkItem to have the work done in a ThreadPool thread and then move onto dequeuing the next TcpClient in its queue. Would you recommend this approach, or is our problem that we're using TcpListener and no amount of rapid dequeueing is going to fix that?

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• WPF MVVM: Convention over Configuration for ResourceDictionary ?

  - by Jeffrey Knight

  Update In the wiki spirit of StackOverflow, here's an update: I spiked Joe White's IValueConverter suggestion below. It works like a charm. I've written a "quickstart" example of this that automates the mapping of ViewModels-Views using some cheap string replacement. If no View is found to represent the ViewModel, it defaults to an "Under Construction" page. I'm dubbing this approach "WPF MVVM White" since it was Joe White's idea. Here are a couple screenshots. The first image is a case of "[SomeControlName]ViewModel" has a corresponding "[SomeControlName]View", based on pure naming convention. The second is a case where the ModelView doesn't have any views to represent it. No more ResourceDictionaries with long ViewModel to View mappings. It's pure naming convention now. I'm hosting a download of the project here: http://rootsilver.com/files/Mvvm.White.Quickstart.zip I'll follow up with a longer blog post walk through. Original Post I read Josh Smith's fantastic MSDN article on WPF MVVM over the weekend. It's destined to be a cult classic. It took me a while to wrap my head around the magic of asking WPF to render the ViewModel. It's like saying "Here's a class, WPF. Go figure out which UI to use to present it." For those who missed this magic, WPF can do this by looking up the View for ModelView in the ResourceDictionary mapping and pulling out the corresponding View. (Scroll down to Figure 10 Supplying a View ). The first thing that jumps out at me immediately is that there's already a strong naming convention of: classNameView ("View" suffix) classNameViewModel ("ViewModel" suffix) My question is: Since the ResourceDictionary can be manipulated programatically, I"m wondering if anyone has managed to Regex.Replace the whole thing away, so the lookup is automatic, and any new View/ViewModels get resolved by virtue of their naming convention? [Edit] What I'm imagining is a hook/interception into ResourceDictionary. ... Also considering a method at startup that uses interop to pull out *View$ and *ViewModel$ class names to build the DataTemplate dictionary in code: //build list foreach .... String.Format("<DataTemplate DataType=\"{x:Type vm:{0} }\"><v:{1} /></DataTemplate>", ...)

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• RMI-applets - Cannot understand error message

  - by aeter

  In a simple RMI game I'm writing (an assignment in uni), I reveice: java.rmi.MarshalException: error marshalling arguments; nested exception is: java.net.SocketException: Broken pipe at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:138) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132) at $Proxy2.drawWorld(Unknown Source) at PlayerServerImpl$1.actionPerformed(PlayerServerImpl.java:180) at javax.swing.Timer.fireActionPerformed(Timer.java:271) at javax.swing.Timer$DoPostEvent.run(Timer.java:201) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) The error message appears after the second Player is registered with the RMI Server and the server starts to send the image (the array of pixels) to the 2 applets. The PlayerImpl and the PlayerServerImpl both extend UnicastRemoteObject. I have been struggling with other error messages for some time now, but I cannot understand how to troubleshoot this one. Please help. The relevant parts of the code are: PlayerServerImpl.java: ... timer = new Timer(10, new ActionListener() { // every 10 milliseconds do: @Override public void actionPerformed(ActionEvent e) { ... BufferedImage buff_image = new BufferedImage(GAME_APPLET_WIDTH, GAME_APPLET_HEIGHT, BufferedImage.TYPE_INT_RGB); // create a graphics context on the buffered image Graphics buff_g = buff_image.createGraphics(); ... // draw the score somewhere on the screen buff_g.drawString(score, GAME_APPLET_WIDTH - 20, 10); ... int[] rgbs = new int[GAME_APPLET_WIDTH * GAME_APPLET_HEIGHT]; int imgPixelsGrabbed[] = buff_image.getRGB(0,0,GAME_APPLET_WIDTH,GAME_APPLET_HEIGHT,rgbs,0,GAME_APPLET_WIDTH); // send the new state to the applets for (Player player : players) { player.drawWorld(imgPixelsGrabbed); System.out.println("Sent image to player"); } PlayerImpl.java: private PlayerApplet applet; public PlayerImpl(PlayerApplet applet) throws RemoteException { super(); this.applet = applet; } ... @Override public void drawWorld(int[] imgPixelsGrabbed) throws RemoteException { applet.setWorld(imgPixelsGrabbed); applet.repaint(); } ... PlayerApplet.java: ... private int[] world; // an array of pixels for the new image to be drawn ... // register players player = new PlayerImpl(applet); String serverIPAddressPort = ipAddressField.getText(); if (validateIPAddressPort(serverIPAddressPort)) { server = (PlayerServer) Naming.lookup("rmi://" + serverIPAddressPort + "/PlayerServer"); server.register(player); idPlayer = server.sendPlayerID(); ... @Override public void update(Graphics g) { buff_img = createImage((ImageProducer) new MemoryImageSource(getWidth(), getHeight(), world, 0, getWidth())); Graphics gr = buff_img.getGraphics(); paint(gr); g.drawImage(buff_img, 0, 0, this); } public void setWorld(int[] world) { this.world = world; }

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• EntityManagerFactory error on Websphere

  - by neverland

  I have a very weird problem. Have an application using Hibernate and spring.I have an entitymanger defined which uses a JNDI lookup .It looks something like this <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="persistenceUnitName" value="ConfigAPPPersist" /> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <property name="showSql" value="true" /> <property name="generateDdl" value="false" /> <property name="databasePlatform" value="org.hibernate.dialect.Oracle9Dialect" /> </bean> </property> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.WebSphereDataSourceAdapter"> <property name="targetDataSource"> <bean class="org.springframework.jndi.JndiObjectFactoryBean"> <property name="jndiName" value="jdbc/pmp" /> </bean> </property> </bean> This application runs fine in DEV. But when we move to higher envs the team that deploys this application does it successfully initially but after a few restarts of the application the entitymanager starts giving this problem Caused by: javax.persistence.PersistenceException: [PersistenceUnit: ConfigAPPPersist] Unable to build EntityManagerFactory at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:677) at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:132) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:224) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:291) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1368) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1334) ... 32 more Caused by: org.hibernate.MappingException: **property mapping has wrong number of columns**: com.***.***.jpa.marketing.entity.MarketBrands.$performasure_j2eeInfo type: object Now you would say this is pretty obvious the entity MarketBrands is incorrect. But its not it maps to the table just fine. And the same code works on DEV. Also the jndi cannot be incorrect since it deploys and works fine initially but throws uo this error after a restart. This is weird and not very logical. But if someone has faced this or has any idea on what might be causing this Please!! help The persistence.xml for the persitence unit has very little <?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0"> <persistence-unit name="ConfigAPPPersist"> <!-- commented code --> </persistence-unit> </persistence>

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• In GWT I'd like to load the main page on www.domain.com and a dynamic page on www.domain.com/xyz - I

  - by Mike Brecht

  Hi, I have a question for which I'm sure there must a simple solution. I'm writing a small GWT application where I want to achieve this: www.domain.com : should serve the welcome page www.domain.com/xyz : should serve page xyz, where xyz is just a key for an item in a database. If there is an item associated with key xyz, I'll load that and show a page, otherwise I'll show a 404 error page. I was trying to modify the web.xml file accordingly but I just couldn't make it work. I could make it work with an url-pattern if the key in question is after another /, for example: www.domain.com/search/xyz. However, I'd like to have the key xyz directly following the root / (http://www.domain.com/xyz). Something like <servlet-mapping> <servlet-name>main</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> doesn't seem to work as I don't know how to address the main page index.html (as it's not an actual servlet) which will then load my main GWT module. I could make it work with a bad work around (see below): Redirecting a 404 exception to index.html and then doing the look up in the main entry point, but I'm sure that's not the best practice, also for SEO purposes. Can anyone give me a hint on how to configure the web.xml with GWT for my purpose? Thanks a lot. Mike Work-around via 404: Web.xml: <web-app> <error-page> <exception-type>404</exception-type> <location>/index.html</location> </error-page> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> </web-app> index.html -- Main Entry point -- onModuleLoad(): String path = Window.Location.getPath(); if (path == null || path.length() == 0 || path.equalsIgnoreCase("/") || path.equalsIgnoreCase("/index.html")) { ... // load main page } else { lookup(path.substring(1)); // that's key xyz

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• agent-based simulation: performance issue: Python vs NetLogo & Repast

  - by max

  I'm replicating a small piece of Sugarscape agent simulation model in Python 3. I found the performance of my code is ~3 times slower than that of NetLogo. Is it likely the problem with my code, or can it be the inherent limitation of Python? Obviously, this is just a fragment of the code, but that's where Python spends two-thirds of the run-time. I hope if I wrote something really inefficient it might show up in this fragment: UP = (0, -1) RIGHT = (1, 0) DOWN = (0, 1) LEFT = (-1, 0) all_directions = [UP, DOWN, RIGHT, LEFT] # point is just a tuple (x, y) def look_around(self): max_sugar_point = self.point max_sugar = self.world.sugar_map[self.point].level min_range = 0 random.shuffle(self.all_directions) for r in range(1, self.vision+1): for d in self.all_directions: p = ((self.point[0] + r * d[0]) % self.world.surface.length, (self.point[1] + r * d[1]) % self.world.surface.height) if self.world.occupied(p): # checks if p is in a lookup table (dict) continue if self.world.sugar_map[p].level > max_sugar: max_sugar = self.world.sugar_map[p].level max_sugar_point = p if max_sugar_point is not self.point: self.move(max_sugar_point) Roughly equivalent code in NetLogo (this fragment does a bit more than the Python function above): ; -- The SugarScape growth and motion procedures. -- to M ; Motion rule (page 25) locals [ps p v d] set ps (patches at-points neighborhood) with [count turtles-here = 0] if (count ps > 0) [ set v psugar-of max-one-of ps [psugar] ; v is max sugar w/in vision set ps ps with [psugar = v] ; ps is legal sites w/ v sugar set d distance min-one-of ps [distance myself] ; d is min dist from me to ps agents set p random-one-of ps with [distance myself = d] ; p is one of the min dist patches if (psugar >= v and includeMyPatch?) [set p patch-here] setxy pxcor-of p pycor-of p ; jump to p set sugar sugar + psugar-of p ; consume its sugar ask p [setpsugar 0] ; .. setting its sugar to 0 ] set sugar sugar - metabolism ; eat sugar (metabolism) set age age + 1 end On my computer, the Python code takes 15.5 sec to run 1000 steps; on the same laptop, the NetLogo simulation running in Java inside the browser finishes 1000 steps in less than 6 sec. EDIT: Just checked Repast, using Java implementation. And it's also about the same as NetLogo at 5.4 sec. Recent comparisons between Java and Python suggest no advantage to Java, so I guess it's just my code that's to blame? EDIT: I understand MASON is supposed to be even faster than Repast, and yet it still runs Java in the end.

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• Spring/RMI server error

  - by 4herpsand7derpsago

  We have a Spring MVC web app (WAR) deploying to Tomcat (6.0.35) that launches a thread inside a separate JVM at deploy time (don't ask why - not my design) and then communicates with that thread via RMI over port 8888. Despite being totally convoluded, this was working perfectly fine up until yesterday, and now the thread is failing at startup and despite our best efforts to add logging into the mix, we are hitting a wall. This is the only exception we are able to find in the logs: Jun 12, 2012 3:11:36 AM com.ourapp.ImageController destroy SEVERE: Shutdown Error: Lookup of RMI stub failed; nested exception is java.rmi.ConnectException: Connection refused to host: localhost; nested exception is: java.net.ConnectException: Connection refused Jun 12, 2012 3:11:37 AM org.apache.catalina.core.StandardContext listenerStop SEVERE: Exception sending context destroyed event to listener instance of class org.springframework.web.context.ContextLoaderListener java.lang.NoClassDefFoundError: org/springframework/web/context/ContextCleanupListener at org.springframework.web.context.ContextLoaderListener.contextDestroyed(ContextLoaderListener.java:80) at org.apache.catalina.core.StandardContext.listenerStop(StandardContext.java:3973) at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4577) at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1165) at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1271) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:296) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1337) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590) at java.lang.Thread.run(Thread.java:662) Caused by: java.lang.ClassNotFoundException: org.springframework.web.context.ContextCleanupListener at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) ... 12 more The ImageController is the Spring MVC Controller that is responsible for kicking off this daemon/spawned RMI thread. Based on the verbage of this error, does anybody have any idea what might be causing this "connection refused" error? Running a netstat -an | grep 8888 (this is a Linux machine) produces no output which means nothing is listening on that port. Thanks in advance for any ideas/suggestions that lead to a fix. Edit: Here's another ConnectionException we're seeing: Caused by: java.net.ConnectException: Connection refused at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351) at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366) at java.net.Socket.connect(Socket.java:529) at java.net.Socket.connect(Socket.java:478) at java.net.Socket.<init>(Socket.java:375) at java.net.Socket.<init>(Socket.java:189) at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22) at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128) at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:595) ... 74 more

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• SaaS Architecture Question from Newbie

  - by user226767

  I have developed a number of departmental client-server applications, and am now ready to begin working on moving one of these applications to a SaaS model. I have done some basic web development, but I'm a newbie when it comes to SaaS architectures. One of the first questions that comes to mind as I try to design the architecture is the question of single vs. multi tenancy. The pros and cons of each vary significantly depending on the type of application and scale required, so I'd like to describe my application and scale needs below, and hope others can comment on how I should get started with the architecture. The client-server application currently consists of a Firebird database and a Windows application. The database contains about 20 tables containing a few thousand records in 4 primary tables, and a few hundred records in various lookup and related tables. Although the number of records is small, the size can get large, as the database can contain large BLOBS. Each customer sets up their own database and has a handful of users within the organization connected to it. When I update the db schema, a new windows application is released, and it checks the db schema and then applies the updates as needed. For the SaaS application, I am designing for 100's (not 1000's or millions) of new customers per year. My first thought was to go with a multi tenancy model to make updates easy (shut down apply the updates to one database, and then start up). On the other hand, a single tenancy model would provide a means to roll updates out to a group of customers at a time, and spread the risk of data corruption - i.e. if something goes wrong with a database, it will impact one customer instead of all customers. With this idea, I was thinking of having a single web front-end which would connect to a single customer database upon login. Thus, when a new customer creates an account, a new database would be created (each customer would have their own db with multiple users as needed for the customer). In this model, a db update would require either a process to go through each db to apply schema changes, or a trigger upon logging in to initiate a schema update similar to the client-server model currently in use. Can anyone point me to information for similar applications which have been ported from client-server to SaaS? Or provide any pointers to consider? Basically I'm looking for architecture examples of taking a departmental application and making it available as a self service website for multiple customers. Thanks for any suggestions, resources, etc.

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• Asynchronous Silverlight 4 call to the World of Warcraft armoury streaming XML in C#

  - by user348446

  Hello - I have been stuck on this all weekend and failed miserably! Please help me to claw back my sanity!! Your challenge For my first Silverlight application I thought it would be fun to use the World of Warcraft armoury to list the characters in my guild. This involves making an asyncronous from Silverlight (duh!) to the WoW armoury which is XML based. SIMPLE EH? Take a look at this link and open the source. You'll see what I mean: http://eu.wowarmory.com/guild-info.xml?r=Eonar&n=Gifted and Talented Below is code for getting the XML (the call to ShowGuildies will cope with the returned XML - I have tested this locally and I know it works). I have not managed to get the expected returned XML at all. Notes: If the browser is capable of transforming the XML it will do so, otherwise HTML will be provided. I think it examines the UserAgent I am a seasoned asp.net web developer C# so go easy if you start talking about native to Windows Forms / WPF I can't seem to set the UserAgent setting in .net 4.0 - doesn't seem to be a property off the HttpWebRequest object for some reason - i think it used to be available. Silverlight 4.0 (created as 3.0 originally before I updated my installation of Silverlight to 4.0) Created using C# 4.0 Please explain as if you talking to a web developer and not a proper programming lol! Below is the code - it should return the XML from the wow armoury. private void button7_Click(object sender, RoutedEventArgs e) { // URL for armoury lookup string url = @"http://eu.wowarmory.com/guild-info.xml?r=Eonar&n=Gifted and Talented"; // Create the web request HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url); // Set the user agent so we are returned XML and not HTML //httpWebRequest.Headers["User-Agent"] = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)"; // Not sure about this dispatcher thing - it's late so i have started to guess. Dispatcher.BeginInvoke(delegate() { // Call asyncronously IAsyncResult asyncResult = httpWebRequest.BeginGetResponse(ReqCallback, httpWebRequest); // End the response and use the result using (HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.EndGetResponse(asyncResult)) { // Load an XML document from a stream XDocument x = XDocument.Load(httpWebResponse.GetResponseStream()); // Basic function that will use LINQ to XML to get the list of characters. ShowGuildies(x); } }); } private void ReqCallback(IAsyncResult asynchronousResult) { // Not sure what to do here - maybe update the interface? } Really hope someone out there can help me! Thanks mucho! Dan. PS Yes, I have noticed the irony in the name of the guild :)

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• ASP.NET MVC & EF4 Entity Framework - Are there any performance concerns in using the entities vs retrieving only the fields i need?

  - by Ant

  Lets say we have 3 tables, Users, Products, Purchases. There is a view that needs to display the purchases made by a user. I could lookup the data required by doing: from p in DBSet<Purchases>.Include("User").Include("Product") select p; However, I am concern that this may have a performance impact because it will retrieve the full objects. Alternatively, I could select only the fields i need: from p in DBSet<Purchases>.Include("User").Include("Product") select new SimplePurchaseInfo() { UserName = p.User.name, Userid = p.User.Id, ProductName = p.Product.Name ... etc }; So my question is: Whats the best practice in doing this? == EDIT Thanks for all the replies. [QUESTION 1]: I want to know whether all views should work with flat ViewModels with very specific data for that view, or should the ViewModels contain the entity objects. Real example: User reviews Products var query = from dr in productRepository.FindAllReviews() where dr.User.UserId = 'userid' select dr; string sql = ((ObjectQuery)query).ToTraceString(); SELECT [Extent1].[ProductId] AS [ProductId], [Extent1].[Comment] AS [Comment], [Extent1].[CreatedTime] AS [CreatedTime], [Extent1].[Id] AS [Id], [Extent1].[Rating] AS [Rating], [Extent1].[UserId] AS [UserId], [Extent3].[CreatedTime] AS [CreatedTime1], [Extent3].[CreatorId] AS [CreatorId], [Extent3].[Description] AS [Description], [Extent3].[Id] AS [Id1], [Extent3].[Name] AS [Name], [Extent3].[Price] AS [Price], [Extent3].[Rating] AS [Rating1], [Extent3].[ShopId] AS [ShopId], [Extent3].[Thumbnail] AS [Thumbnail], [Extent3].[Creator_UserId] AS [Creator_UserId], [Extent4].[Comment] AS [Comment1], [Extent4].[DateCreated] AS [DateCreated], [Extent4].[DateLastActivity] AS [DateLastActivity], [Extent4].[DateLastLogin] AS [DateLastLogin], [Extent4].[DateLastPasswordChange] AS [DateLastPasswordChange], [Extent4].[Email] AS [Email], [Extent4].[Enabled] AS [Enabled], [Extent4].[PasswordHash] AS [PasswordHash], [Extent4].[PasswordSalt] AS [PasswordSalt], [Extent4].[ScreenName] AS [ScreenName], [Extent4].[Thumbnail] AS [Thumbnail1], [Extent4].[UserId] AS [UserId1], [Extent4].[UserName] AS [UserName] FROM [ProductReviews] AS [Extent1] INNER JOIN [Users] AS [Extent2] ON [Extent1].[UserId] = [Extent2].[UserId] LEFT OUTER JOIN [Products] AS [Extent3] ON [Extent1].[ProductId] = [Extent3].[Id] LEFT OUTER JOIN [Users] AS [Extent4] ON [Extent1].[UserId] = [Extent4].[UserId] WHERE N'615005822' = [Extent2].[UserId] or from d in productRepository.FindAllProducts() from dr in d.ProductReviews where dr.User.UserId == 'userid' orderby dr.CreatedTime select new ProductReviewInfo() { product = new SimpleProductInfo() { Id = d.Id, Name = d.Name, Thumbnail = d.Thumbnail, Rating = d.Rating }, Rating = dr.Rating, Comment = dr.Comment, UserId = dr.UserId, UserScreenName = dr.User.ScreenName, UserThumbnail = dr.User.Thumbnail, CreateTime = dr.CreatedTime }; SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[Thumbnail] AS [Thumbnail], [Extent1].[Rating] AS [Rating], [Extent2].[Rating] AS [Rating1], [Extent2].[Comment] AS [Comment], [Extent2].[UserId] AS [UserId], [Extent4].[ScreenName] AS [ScreenName], [Extent4].[Thumbnail] AS [Thumbnail1], [Extent2].[CreatedTime] AS [CreatedTime] FROM [Products] AS [Extent1] INNER JOIN [ProductReviews] AS [Extent2] ON [Extent1].[Id] = [Extent2].[ProductId] INNER JOIN [Users] AS [Extent3] ON [Extent2].[UserId] = [Extent3].[UserId] LEFT OUTER JOIN [Users] AS [Extent4] ON [Extent2].[UserId] = [Extent4].[UserId] WHERE N'userid' = [Extent3].[UserId] ORDER BY [Extent2].[CreatedTime] ASC [QUESTION 2]: Whats with the ugly outer joins?

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• xsl key - multiple levels for an element

  - by user1004770

  My previous post was not very meaningful. reposting here. What i am looking for is the QueueManager element, under SORRegion name="default"(which is the parent), within inan.xml. I have used xsl key. In my xsl the value 'default' is hardcoded. here is the xsl i used <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" > <xsl:output omit-xml-declaration="yes" indent="yes" method="xml" /> <xsl:key name="CR-lookup" match="Service" use="concat(@ServiceName, '+', SOR/@SORname, '+', */CountryCode/@Ctrycd, '+', */*/SORRegion/@name, '+', */*/*/ConsumerName/@name)"/> <xsl:variable name="CRTable" select="document('inan.xml')"/> <xsl:template match="/"> <Contributor> <ContributorRole> <xsl:for-each select="$CRTable"> <!-- change context document --> <xsl:for-each select="key('CR-lookup', concat('StatementIndicatorsService', '+', 'Globestar', '+', '124', '+', 'default', '+', 'MYCA'))"> <a> <xsl:value-of select="*/*/*/*/QueueManager"/> </a> </xsl:for-each> </xsl:for-each> </ContributorRole> </Contributor> </xsl:template> </xsl:stylesheet> any input xml file is fine. here is my actual output <Contributor> <ContributorRole /> </Contributor> expected output <Contributor> <ContributorRole> <a>MAO1</a> </ContributorRole> </Contributor> inan.xml document <RoutingDetails> <Service ServiceName="StatementIndicatorsService"> <SOR SORname="Globestar"> <CountryCode Ctrycd="124"> <SORRegion name="Test"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146B</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146C</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="default"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKBX1"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKAX4"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO204.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKEX7"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO247.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> </CountryCode> <CountryCode Ctrycd="826"> <SORRegion name="Test"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="default"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKBX1"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKAX4"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO204.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKEX7"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA1146A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA1146A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO247.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> </CountryCode> <CountryCode Ctrycd="724"> <SORRegion name="Test"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA4248A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA4248A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO239.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="default"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA4248A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA4248A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO239.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKBX1"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA4248A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA4248A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.ICS.DP.DHIPO211.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKAX4"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA4248A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA4248A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO204.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> <SORRegion name="CICDKEX7"> <ConsumerName name="MYCA"> <AutomationIds> <PreAutoId> <AutomationId>XA4248A</AutomationId> <AutomationId>XA1146A</AutomationId> </PreAutoId> <DefaultAutoId> <AutomationId>XA4248A</AutomationId> </DefaultAutoId> </AutomationIds> </ConsumerName> <QueueDetails> <QueueManager>MAO1</QueueManager> <ReplyQueueManager>MAO1</ReplyQueueManager> <RequestQueue>GSTAR.GDAS.DHIPO247.REQUEST</RequestQueue> <ReplyQueue>ICS.DP.REPLY</ReplyQueue> </QueueDetails> </SORRegion> </CountryCode> </SOR> </Service> </RoutingDetails>

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• Choosing the right .NET architecture. WCF? WPF/Forms, ASP.NET (MVC)?

  - by Tommy Jakobsen

  I’m in the situation that I have to design and implement a rather big system from the bottom. I’m having some (a lot actually) questions about the architecture that I would like your comments and thoughts on. I don’t hope that I’ve written too much here, but I wanted to give you all an idea of what the system is. Quick info about the applications, read if you want: I can’t share much detail about the project, but basically it’s a system where we offer our customer a service to manage their users. We have a hotline where the users call and our hotline uses an (windows) application (intranet) to manage the user’s data, etc. The customer also has a web application where they can see reports, information about their business and users, and the ability to modify their data. Modifying data is not just user data like address and so, but also information about the products/services the user has, which can be complicated. The applications will be built on Microsoft .NET Framework 4, with a MS SQL Server 2008 database. There will be a few applications that have to access this database, such as: Intranet application (used by us and our hotline) Customer web application type 1 Customer web application type 2 Customer web application type n different applications) … Now my big problem is what .NET parts I should use for such a system. For the “backend” I’ve considered using Windows Communication Foundation: Would WCF be a good choice? The intranet application will be an application that has to edit lots of records in the database. It has to be easy to navigate using the keyboard (fast to work with). Has a feature such as “find customer, find that, lookup this, choose this and update that”. What would be the best choice to develop this application in? Would it be WPF or good old Windows Forms? I don’t need all of the fancy graphics features in WPF, like 3D, but the application has to look nice (maybe something like the new Visual Studio/Office tools). And the same question goes for the web pages. They have much the same work to do, but not as many features as the intranet application, and not the same amount of data (much less). That is my questions for now. I’m hoping to get a discussion going that will open my eyes to some of these technologies, helping me decide architecture to go with. I would like to say thanks in advance, and let you all know that any thoughts will be much appreciated.

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• Autocomplete server-side implementation

  - by toluju

  What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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• Clojure vars and Java static methods

  - by j-g-faustus

  I'm a few days into learning Clojure and are having some teething problems, so I'm asking for advice. I'm trying to store a Java class in a Clojure var and call its static methods, but it doesn't work. Example: user=> (. java.lang.reflect.Modifier isPrivate 1) false user=> (def jmod java.lang.reflect.Modifier) #'user/jmod user=> (. jmod isPrivate 1) java.lang.IllegalArgumentException: No matching method found: isPrivate for class java.lang.Class (NO_SOURCE_FILE:0) at clojure.lang.Compiler.eval(Compiler.java:4543) From the exception it looks like the runtime expects a var to hold an object, so it calls .getClass() to get the class and looks up the method using reflection. In this case the var already holds a class, so .getClass() returns java.lang.Class and the method lookup obviously fails. Is there some way around this, other than writing my own macro? In the general case I'd like to have either an object or a class in a varible and call the appropriate methods on it - duck typing for static methods as well as for instance methods. In this specific case I'd just like a shorter name for java.lang.reflect.Modifier, an alias if you wish. I know about import, but looking for something more general, like the Clojure namespace alias but for Java classes. Are there other mechanisms for doing this? Edit: Maybe I'm just confused about the calling conventions here. I thought the Lisp (and by extension Clojure) model was to evaluate all arguments and call the first element in the list as a function. In this case (= jmod java.lang.reflect.Modifier) returns true, and (.getName jmod) and (.getName java.lang.reflect.Modifier) both return the same string. So the variable and the class name clearly evaluate to the same thing, but they still cannot be called in the same fashion. What's going on here? Edit 2 Answering my second question (what is happening here), the Clojure doc says that If the first operand is a symbol that resolves to a class name, the access is considered to be to a static member of the named class... Otherwise it is presumed to be an instance member http://clojure.org/java_interop under "The Dot special form" "Resolving to a class name" is apparently not the same as "evaluating to something that resolves to a class name", so what I am trying to do here is something the dot special form does not support.

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• WLI domain with 3 servers - issues on JPD process startup

  - by XpiritO

  Hi there. I'm currently working on a clustered WLI environment which comprehends 3 servers: 1 admin server ("AdminServer") and 2 managed servers ("mn1" and "mn2") grouped as a cluster, as follows: Architecture diagram: http://img72.imageshack.us/img72/4112/clusterdiagram.jpg I've developed a JPD process to execute some scheduled tasks, invoked using a Message Broker. I've deployed this project into a single-server WLI domain (with AdminServer only) and it works as expected: the JPD process is invoked (I've configured a Timer Event Generator instance to start it up). Message broker: http://img532.imageshack.us/img532/1443/wlimessagebroker.jpg Timer event generator: http://img408.imageshack.us/img408/7358/wlitimereventgenerator.jpg In order to achieve fail-over and load-balancing capabilities, I'm currently trying to deploy this JPD process into this clustered WLI environment. Although, I'm having some issues with this, as I cannot get it to work properly, even if it still works. Here is a screenshot of the "WLI Process Instance Monitor" (with AdminServer and mn1 instances up and running): http://img710.imageshack.us/img710/8477/wliprocessinstancemonit.jpg According to this screen the process seems to be running, as it shows in this instance monitor screen. However, I don't see any output coming out neither at AdminServer console or mn1 console. In single-server domain it was visible output from JPD process "timeout" callback method, wich implementation is shown below: @com.bea.wli.control.broker.MessageBroker.StaticSubscription(xquery = "", filterValueMatch = "", channelName = "/SamplePrefix/Samples/SampleStringChannel", messageBody = "{x0}") public void subscription(java.lang.String x0) { String toReturn=""; try { Context myCtx = new InitialContext(); MBeanHome mbeanHome = (MBeanHome)myCtx.lookup("weblogic.management.home.localhome"); toReturn=mbeanHome.getMBeanServer().getServerName(); System.out.println("**** executed at **** " + System.currentTimeMillis() + " by: " + toReturn); } catch (Exception e) { System.out.println("Exception!"); e.printStackTrace(); } } (...) @org.apache.beehive.controls.api.events.EventHandler(field = "myT", eventSet = com.bea.control.WliTimerControl.Callback.class, eventName = "onTimeout") public void myT_onTimeout(long time, java.io.Serializable data) { // #START: CODE GENERATED - PROTECTED SECTION - you can safely add code above this comment in this method. #// // input transform System.out.println("**** published at **** " + System.currentTimeMillis()); publishControl.publish("aaaa"); // parameter assignment // #END : CODE GENERATED - PROTECTED SECTION - you can safely add code below this comment in this method. #// } and here is the output visible at "AdminServer" console in single-server domain testing: **** published at **** 1273238090713 **** executed at **** 1273238132123 by: AdminServer **** published at **** 1273238152462 **** executed at **** 1273238152562 by: AdminServer (...) What may be wrong with my clustered configuration? Am I missing something to accomplish clustered deployment? Thanks in advance for your help.

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• Moving a unit precisely along a path in x,y coordinates

  - by Adam Eberbach

  I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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• Strange problem publishing a fresh Ruby on Rails 3 application on localhost (Apache, Passenger and VirtualHosts)

  - by user502052

  I recently created a new Ruby on Rails 3 application locally on a Mac OS, named "test". Since I use apache2, in the private/etc/apache2/httpd.conf I set the VirtualHost for the "test" application: <VirtualHost *:443> ServerName test.pjtmain.localhost:443 DocumentRoot "/Users/<my_user_name>/Sites/test/public" RackEnv development <Directory "/Users/<my_user_name>/Sites/test/public"> Order allow,deny Allow from all </Directory> # SSL Configuration SSLEngine on ... </VirtualHost> <VirtualHost *:80> ServerName test.pjtmain.localhost DocumentRoot "/Users/<my_user_name>/Sites/test/public" RackEnv development <Directory "/Users/<my_user_name>/Sites/test/public"> Order allow,deny Allow from all </Directory> </VirtualHost> Of course I restart apache2, but trying to access to http://test.pjtmain.localhost/ I have this error message from: FIREFOX Oops! Firefox could not find test.pjtmain.localhost Suggestions: * Search on Google: ... SAFARI Safari can’t find the server. Safari can’t open the page “http://test.pjtmain.localhost/” because Safari can’t find the server “test.pjtmain.localhost”. I have other RoR3 applications setted like that above in the httpd.conf file and all them work. What is the problem (maybe it is not related to apache...)? Notes: 1. Using the 'Network Uility' I did a Ping with the following result: ping: cannot resolve test.pjtmain.localhost: Unknown host and I did a Lookup with the follonwing result: ; <<>> DiG 9.6.0-APPLE-P2 <<>> test.pjtmain.localhost +multiline +nocomments +nocmd +noquestion +nostats +search ;; global options: +cmd <MY_BROADBAND_TELECOMUNICATIONS_COMPANY_NAME>.com. 115 IN SOA dns1.<MY_BROADBAND_TELECOMUNICATIONS_COMPANY_NAME>.com. dnsmaster.<MY_BROADBAND_TELECOMUNICATIONS_COMPANY_NAME>.com. ( 2010110500 ; serial 10800 ; refresh (3 hours) 900 ; retry (15 minutes) 604800 ; expire (1 week) 86400 ; minimum (1 day) ) 2. I am using Phusion Passenger 3. Since I not changed nothing to the new "test" application, I expect to see the default RoR index.html page: 4. It seems that in the 'Console Messages' there is any warning or error

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• Cepstral Analysis for pitch detection

  - by Ohmu

  Hi! I'm looking to extract pitches from a sound signal. Someone on IRC just explain to me how taking a double FFT achieves this. Specifically: take FFT take log of square of absolute value (can be done with lookup table) take another FFT take absolute value I am attempting this using vDSP I can't understand how I didn't come across this technique earlier. I did a lot of hunting and asking questions; several weeks worth. More to the point, I can't understand why I didn't think of it. I am attempting to achieve this with vDSP library. it looks as though it has functions to handle all of these tasks. However, I'm wondering about the accuracy of the final result. I have previously used a technique which scours the frequency bins of a single FFT for local maxima. when it encounters one, it uses a cunning technique (the change in phase since the last FFT) to more accurately place the actual peak within the bin. I am worried that this precision will be lost with this technique I'm presenting here. I guess the technique could be used after the second FFT to get the fundamental accurately. But it kind of looks like the information is lost in step 2. as this is a potentially tricky process, could someone with some experience just look over what I'm doing and check it for sanity? also, I've heard there is an alternative technique involving fitting a quadratic over neighbouring bins. Is this of comparable accuracy? if so, I would favour it, as it doesn't involve remembering bin phases. so questions: does this approach makes sense? Can it be improved? I'm a bit worried about And the log square component; there seems to be a vDSP function to do exactly that: vDSP_vdbcon however, there is no indication it precalculates a log-table -- I assume it doesn't, as the FFT function requires an explicit pre-calculation function to be called and passed into it. and this function doesn't. Is there some danger of harmonics being picked up? is there any cunning way of making vDSP pull out the maxima, biggest first? Can anyone point me towards some research or literature on this technique? the main question: is it accurate enough? Can the accuracy be improved? I have just been told by an expert that the accuracy IS INDEED not sufficient. Is this the end of the line? Pi PS I get SO annoyed (npi) when I want to create tags, but cannot. :| I have suggested to the maintainers that SO keep track of attempted tags, but I'm sure I was ignored. we need tags for vDSP, accelerate framework, cepstral analysis

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• approximating log10[x^k0 + k1]

  - by Yale Zhang

  Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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• Scalable Database Tagging Schema

  - by Longpoke

  EDIT: To people building tagging systems. Don't read this. It is not what you are looking for. I asked this when I wasn't aware that RDBMS all have their own optimization methods, just use a simple many to many scheme. I have a posting system that has millions of posts. Each post can have an infinite number of tags associated with it. Users can create tags which have notes, date created, owner, etc. A tag is almost like a post itself, because people can post notes about the tag. Each tag association has an owner and date, so we can see who added the tag and when. My question is how can I implement this? It has to be fast searching posts by tag, or tags by post. Also, users can add tags to posts by typing the name into a field, kind of like the google search bar, it has to fill in the rest of the tag name for you. I have 3 solutions at the moment, but not sure which is the best, or if there is a better way. Note that I'm not showing the layout of notes since it will be trivial once I get a proper solution for tags. Method 1. Linked list tagId in post points to a linked list in tag_assoc, the application must traverse the list until flink=0 post: id, content, ownerId, date, tagId, notesId tag_assoc: id, tagId, ownerId, flink tag: id, name, notesId Method 2. Denormalization tags is simply a VARCHAR or TEXT field containing a tab delimited array of tagId:ownerId. It cannot be a fixed size. post: id, content, ownerId, date, tags, notesId tag: id, name, notesId Method 3. Toxi (from: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html, also same thing here: http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging) post: id, content, ownerId, date, notesId tag_assoc: ownerId, tagId, postId tag: id, name, notesId Method 3 raises the question, how fast will it be to iterate through every single row in tag_assoc? Methods 1 and 2 should be fast for returning tags by post, but for posts by tag, another lookup table must be made. The last thing I have to worry about is optimizing searching tags by name, I have not worked that out yet. I made an ASCII diagram here: http://pastebin.com/f1c4e0e53

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• NHibernate and objects with value-semantics

  - by Groo

  Problem: If I pass a class with value semantics (Equals method overridden) to NHibernate, NHibernate tries to save it to db even though it just saved an entity equal by value (but not by reference) to the database. What am I doing wrong? Here is a simplified example model for my problem: Let's say I have a Person entity and a City entity. One thread (producer) is creating new Person objects which belong to a specific existing City, and another thread (consumer) is saving them to a repository (using NHibernate as DAL). Since there is lot of objects being flushed at a time, I am using Guid.Comb id's to ensure that each insert is made using a single SQL command. City is an object with value-type semantics (equal by name only -- for this example purposes only): public class City : IEquatable<City> { public virtual Guid Id { get; private set; } public virtual string Name { get; set; } public virtual bool Equals(City other) { if (other == null) return false; return this.Name == other.Name; } public override bool Equals(object obj) { return Equals(obj as City); } public override int GetHashCode() { return this.Name.GetHashCode(); } } Fluent NH mapping is something like: public class PersonMap : ClassMap<Person> { public PersonMap() { Id(x => x.Id) .GeneratedBy.GuidComb(); References(x => x.City) .Cascade.SaveUpdate(); } } public class CityMap : ClassMap<City> { public CityMap() { Id(x => x.Id) .GeneratedBy.GuidComb(); Map(x => x.Name); } } Right now (with my current NHibernate mapping config), my consumer thread maintains a dictionary of cities and replaces their references in incoming person objects (otherwise NHibernate will see a new, non-cached City object and try to save it as well), and I need to do it for every produced Person object. Since I have implemented City class to behave like a value type, I hoped that NHibernate would compare Cities by value and not try to save them each time -- i.e. I would only need to do a lookup once per session and not care about them anymore. Is this possible, and if yes, what am I doing wrong here?

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• Postgresql count+sort performance

  - by invictus

  I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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• Read from file in eclipse

  - by Buzkie

  I'm trying to read from a text file to input data to my java program. However, eclipse continuosly gives me a Source not found error no matter where I put the file. I've made an additional sources folder in the project directory, the file in question is in both it and the bin file for the project and it still can't find it. I even put a copy of it on my desktop and tried pointing eclipse there when it asked me to browse for the source lookup path. No matter what I do it can't find the file. here's my code in case it's pertinent: System.out.println(System.getProperty("user.dir")); File file = new File("file.txt"); Scanner scanner = new Scanner(file); in addition, it says the user directory is the project directory and there is a copy there too. I have no clue what to do. Thanks, Alex after attempting the suggestion below and refreshing again, I was greeted by a host of errors. FileNotFoundException(Throwable).<init>(String) line: 195 FileNotFoundException(Exception).<init>(String) line: not available FileNotFoundException(IOException).<init>(String) line: not available FileNotFoundException.<init>(String) line: not available URLClassPath$JarLoader.getJarFile(URL) line: not available URLClassPath$JarLoader.access$600(URLClassPath$JarLoader, URL) line: not available URLClassPath$JarLoader$1.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>) line: not available [native method] URLClassPath$JarLoader.ensureOpen() line: not available URLClassPath$JarLoader.<init>(URL, URLStreamHandler, HashMap) line: not available URLClassPath$3.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>) line: not available [native method] URLClassPath.getLoader(URL) line: not available URLClassPath.getLoader(int) line: not available URLClassPath.access$000(URLClassPath, int) line: not available URLClassPath$2.next() line: not available URLClassPath$2.hasMoreElements() line: not available ClassLoader$2.hasMoreElements() line: not available CompoundEnumeration<E>.next() line: not available CompoundEnumeration<E>.hasMoreElements() line: not available ServiceLoader$LazyIterator.hasNext() line: not available ServiceLoader$1.hasNext() line: not available LocaleServiceProviderPool$1.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>) line: not available [native method] LocaleServiceProviderPool.<init>(Class<LocaleServiceProvider>) line: not available LocaleServiceProviderPool.getPool(Class<LocaleServiceProvider>) line: not available NumberFormat.getInstance(Locale, int) line: not available NumberFormat.getNumberInstance(Locale) line: not available Scanner.useLocale(Locale) line: not available Scanner.<init>(Readable, Pattern) line: not available Scanner.<init>(ReadableByteChannel) line: not available Scanner.<init>(File) line: not available code used: System.out.println(System.getProperty("user.dir")); File file = new File(System.getProperty("user.dir") + "/file.txt"); Scanner scanner = new Scanner(file);

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