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  • Subterranean IL: The ThreadLocal type

    - by Simon Cooper
    I came across ThreadLocal<T> while I was researching ConcurrentBag. To look at it, it doesn't really make much sense. What's all those extra Cn classes doing in there? Why is there a GenericHolder<T,U,V,W> class? What's going on? However, digging deeper, it's a rather ingenious solution to a tricky problem. Thread statics Declaring that a variable is thread static, that is, values assigned and read from the field is specific to the thread doing the reading, is quite easy in .NET: [ThreadStatic] private static string s_ThreadStaticField; ThreadStaticAttribute is not a pseudo-custom attribute; it is compiled as a normal attribute, but the CLR has in-built magic, activated by that attribute, to redirect accesses to the field based on the executing thread's identity. TheadStaticAttribute provides a simple solution when you want to use a single field as thread-static. What if you want to create an arbitary number of thread static variables at runtime? Thread-static fields can only be declared, and are fixed, at compile time. Prior to .NET 4, you only had one solution - thread local data slots. This is a lesser-known function of Thread that has existed since .NET 1.1: LocalDataStoreSlot threadSlot = Thread.AllocateNamedDataSlot("slot1"); string value = "foo"; Thread.SetData(threadSlot, value); string gettedValue = (string)Thread.GetData(threadSlot); Each instance of LocalStoreDataSlot mediates access to a single slot, and each slot acts like a separate thread-static field. As you can see, using thread data slots is quite cumbersome. You need to keep track of LocalDataStoreSlot objects, it's not obvious how instances of LocalDataStoreSlot correspond to individual thread-static variables, and it's not type safe. It's also relatively slow and complicated; the internal implementation consists of a whole series of classes hanging off a single thread-static field in Thread itself, using various arrays, lists, and locks for synchronization. ThreadLocal<T> is far simpler and easier to use. ThreadLocal ThreadLocal provides an abstraction around thread-static fields that allows it to be used just like any other class; it can be used as a replacement for a thread-static field, it can be used in a List<ThreadLocal<T>>, you can create as many as you need at runtime. So what does it do? It can't just have an instance-specific thread-static field, because thread-static fields have to be declared as static, and so shared between all instances of the declaring type. There's something else going on here. The values stored in instances of ThreadLocal<T> are stored in instantiations of the GenericHolder<T,U,V,W> class, which contains a single ThreadStatic field (s_value) to store the actual value. This class is then instantiated with various combinations of the Cn types for generic arguments. In .NET, each separate instantiation of a generic type has its own static state. For example, GenericHolder<int,C0,C1,C2> has a completely separate s_value field to GenericHolder<int,C1,C14,C1>. This feature is (ab)used by ThreadLocal to emulate instance thread-static fields. Every time an instance of ThreadLocal is constructed, it is assigned a unique number from the static s_currentTypeId field using Interlocked.Increment, in the FindNextTypeIndex method. The hexadecimal representation of that number then defines the specific Cn types that instantiates the GenericHolder class. That instantiation is therefore 'owned' by that instance of ThreadLocal. This gives each instance of ThreadLocal its own ThreadStatic field through a specific unique instantiation of the GenericHolder class. Although GenericHolder has four type variables, the first one is always instantiated to the type stored in the ThreadLocal<T>. This gives three free type variables, each of which can be instantiated to one of 16 types (C0 to C15). This puts an upper limit of 4096 (163) on the number of ThreadLocal<T> instances that can be created for each value of T. That is, there can be a maximum of 4096 instances of ThreadLocal<string>, and separately a maximum of 4096 instances of ThreadLocal<object>, etc. However, there is an upper limit of 16384 enforced on the total number of ThreadLocal instances in the AppDomain. This is to stop too much memory being used by thousands of instantiations of GenericHolder<T,U,V,W>, as once a type is loaded into an AppDomain it cannot be unloaded, and will continue to sit there taking up memory until the AppDomain is unloaded. The total number of ThreadLocal instances created is tracked by the ThreadLocalGlobalCounter class. So what happens when either limit is reached? Firstly, to try and stop this limit being reached, it recycles GenericHolder type indexes of ThreadLocal instances that get disposed using the s_availableIndices concurrent stack. This allows GenericHolder instantiations of disposed ThreadLocal instances to be re-used. But if there aren't any available instantiations, then ThreadLocal falls back on a standard thread local slot using TLSHolder. This makes it very important to dispose of your ThreadLocal instances if you'll be using lots of them, so the type instantiations can be recycled. The previous way of creating arbitary thread-static variables, thread data slots, was slow, clunky, and hard to use. In comparison, ThreadLocal can be used just like any other type, and each instance appears from the outside to be a non-static thread-static variable. It does this by using the CLR type system to assign each instance of ThreadLocal its own instantiated type containing a thread-static field, and so delegating a lot of the bookkeeping that thread data slots had to do to the CLR type system itself! That's a very clever use of the CLR type system.

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  • Servlet 3 spec and ThreadLocal

    - by mindas
    As far as I know, Servlet 3 spec introduces asynchronous processing feature. Among other things, this will mean that the same thread can and will be reused for processing another, concurrent, HTTP request(s). This isn't revolutionary, at least for people who worked with NIO before. Anyway, this leads to another important thing: no ThreadLocal variables as a temporary storage for the request data. Because if the same thread suddenly becomes the carrier thread to a different HTTP request, request-local data will be exposed to another request. All of that is my pure speculation based on reading articles, I haven't got time to play with any Servlet 3 implementations (Tomcat 7, GlassFish 3.0.X, etc.). So, the questions: Am I correct to assume that ThreadLocal will cease to be a convenient hack to keep the request data? Has anybody played with any of Servlet 3 implementations and tried using ThreadLocals to prove the above? Apart from storing data inside HTTP Session, are there any other similar easy-to-reach hacks you could possibly advise?

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  • Why should Java ThreadLocal variables be static

    - by kellyfj
    I was reading that JavaDoc for Threadlocal here http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ThreadLocal.html and it says "ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread (e.g., a user ID or Transaction ID). " But my question is why did they choose to make it static (typically) - it makes it a bit confusing to have "per thread" state but its static?

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  • Why does every thread in my application use a different hibernate session?

    - by Ittai
    Hi, I have a web-application which uses hibernate and for some reason every thread (httprequest or other threads related to queueing) uses a different session. I've implemented a HibernateSessionFactory class which looks like this: public class HibernateSessionFactory { private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static Configuration configuration = new AnnotationConfiguration(); private static org.hibernate.SessionFactory sessionFactory; static { try { configuration.configure(configFile); sessionFactory = configuration.buildSessionFactory(); } catch (Exception e) {} } private HibernateSessionFactory() {} public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get(); if (session == null || !session.isOpen()) { if (sessionFactory == null) { rebuildSessionFactory();//This method basically does what the static init block does } session = (sessionFactory != null) ? sessionFactory.openSession(): null; threadLocal.set(session); } return session; } //More non relevant methods here. Now from my testing it seems that the threadLocal member is indeed initialized only once when the class is first loaded by the JVM but for some reason when different threads access the getSession() method they use different sessions. When a thread first accesses this class (Session) threadLocal.get(); will return null but as expected all other access requests will yeild the same session. I'm not sure how this can be happening as the threadLocal variable is final and the method threadLocal.set(session) is only used in the above context (which I'm 99.9% sure has to yeild a non null session as I would have encountered a NullPointerException at a different part of my app). I'm not sure this is relevant but these are the main parts of my hibernate.cfg.xml file: <hibernate-configuration> <session-factory> <property name="connection.url">someURL</property> <property name="connection.driver_class"> com.microsoft.sqlserver.jdbc.SQLServerDriver</property> <property name="dialect">org.hibernate.dialect.SQLServerDialect</property> <property name="hibernate.connection.isolation">1</property> <property name="hibernate.connection.username">User</property> <property name="hibernate.connection.password">Password</property> <property name="hibernate.connection.pool_size">10</property> <property name="show_sql">false</property> <property name="current_session_context_class">thread</property> <property name="hibernate.hbm2ddl.auto">update</property> <property name="hibernate.cache.use_second_level_cache">false</property> <property name="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <!-- Mapping files --> I'd appreciate any help granted and of course if anyone has any questions I'd be happy to clarify. Ittai

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  • ?????????OutOfMemory?????????????????|WebLogic Channel|??????

    - by ???02
    WebLogic Server Enterprise Edition????????????JRockit Mission Control????????????????????????????????????????????????????????????????????????????????Application Grid???????? ????????????????? ???(?????? Fusion Middleware?????? ???????????)??????????????????JRockit Mission Control?????2?????(???)????????????OutOfMemory???????? Java????????????????????1????????????????????????OutOfMemory?????????????·??????JVM????????????????????????????????????????????????B?????OutOfMemory???????????? B????????????????·?????????????????????????WebLogic Server???????????????OutOfMemory??????????????????????????????????????????????????????????????????????????????????????????????????????? ????B???????????????JRockit Mission Control?1??????Memory Leak Detector?????OutOfMemory???????????????Memory Leak Detector?Java????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????? Memory Leak Detector?????????????????????????????????????(byte[])???????????????????????????????????·??????(GC)???????????????????????????????? ????????????????????????????????????????????????Memory Leak Detector????·??????????·??????????????????????????????????????????????????????????????ThreadLocal??????????????????????????40%??????????????????java.lang.ThreadLocal????????? WebLogic Server???Java EE????????·????????????????/??????????????????????????????????????·???????????????????????·????ThreadLocal?????????????·???????????????????????·?????????????????ThreadLocal???????????????????????????ThreadLocal?????????????????????????????? ???????ThreadLocal?????????????????Memory Leak Detector?????????????????????·?????????????????????????????(ThreadLocal???????????????)???????·????????????????????????????????????????????????????????????1????????????1?????·????????????????????????????????????????????·???????????????? ??B???????WebLogic Server???????????????????????????????WebLogic Server????2???????????????????????????????????????????????????????????????????1?????????????2?????·?????????????2?????????·??????????? ???ThreadLocal???????????????ThreadLocal????????????????Thread??????????????????????????????????????Thread???????????????????GC?????????????????GC????????????????????????·?????????????????????????????????????????????·?????????????????????????????(????????·???·???·????)? WebLogic Server???????????????????????????????????????????????(?????????????????)???"????"?????????????????????????????GC??????????ThreadLocal???????????????????????????????????????GC?????????????????????????????????????????????????????????????????????????????????OutOfMemory????????????????? ??????????????????JRockit Flight Recorder?JRockit Mission Control????????????????????????????????????ThreadLocal????????????????????????????·???·????????????????????????????JRockit Flight Recorder/JRockit Mission Control????????WebLogic Server?????????????????????????????????·???????????????? ????????????????????????????·???????????C??????????WebLogic Server??????????????????????????????????????????????4??(1????×4??)??????12??(2????×6??)??????????? ??????????3?????????????????????????????????????????????????4??·???????3,500??????????????12??????????2,000??????????????????? ???C??????????JVM????·????GC?????????????????????????OS???????????·?????????????????????????????????????????????? ???????????????????????JRockit Flight Recorder?????????????????????????????????????·?????????????????30?????????????????????? ???????????????????1?????????????????????(??????·?????)?????????????????????WebLogic Server??????????????????????????????????????????·????????????????????? ???????????????????????????????????????????????????????Spin(???)??????????????????·???????????????????????????????????????????????????????????·???????????????JRockit Flight Recorder??????????????????12??????????????·??????????????????(4??/1 JVM)????Java???·????????????(12??/1 JVM)????Java???·???????? ??????·?????????CPU????????????????????????????·???????????????????????????????CPU??????????????????????????????????????????????????????·?????????????????????????????·???? ?????????·??????????????????·????????????????????????????????????????????????????????????·??????????????????????????????????·?????????????????????·?????????????????(?????????????·???????????????????)? WebLogic Server?JVM???Oracle JRockit???CPU???????JVM?????????????JVM?????????????????????????????????????????????????(JVM????-XX:BindToCPUs???????????CPU?????????JVM???-XX:NumaMemoryPolicy=strictlocal???????????????·?????????)??????????·???????????????????????????????(12??/1 JVM)????Java???·????????(?????)*   *   * ??????????3?????????????????????????????????????????????????WebLogic Server????OS?????????????????????????????????JRockit Flight Recorder??????????????JRockit Mission Control???????????????????????????????????????????WebLogic Server?????????????????????????????????????JRockit Flight Recorder /JRockit Mission Control??????????????????????????????????????????????????????????????????????????????????????

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  • What are the pros and cons of using an in memeory DB rather than a ThreadLocal

    - by Pangea
    we have been using ThreadLocal so far to carry some data so as to not clutter the API. However below are some of issues of using thread local that which I dont like 1) over the years the data items being carried in thread local has increased 2) Since we started using threads (for some light weight processing), we have also migrating these data to the threads in the pool and copying them back again I am thinking of using an in memory DB for these (we doesnt want to add this to the API). I wondering if this approach is good. What r the pros and cons. thx in advance.

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  • What are the pros and cons of using an in memory DB rather than a ThreadLocal

    - by Pangea
    We have been using ThreadLocal so far to carry some data so as to not clutter the API. However below are some of issues of using thread local that which I don't like: 1) Over the years the data items being carried in thread local has increased 2) Since we started using threads (for some light weight processing), we have also migrating these data to the threads in the pool and copying them back again I am thinking of using an in memory DB for these (we doesn't want to add this to the API). I wondering if this approach is good. What are the pros and cons? thx in advance.

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  • When should ThreadLocal be used instead of Thread.SetData/Thread.GetData?

    - by Jon Ediger
    Prior to .net 4.0, I implemented a solution using named data slots in System.Threading.Thread. Now, in .net 4.0, there is the idea of ThreadLocal. How does ThreadLocal usage compare to named data slots? Does the ThreadLocal value get inherited by children threads? Is the idea that ThreadLocal is a simplified version of using named data slots? An example of some stuff using named data slots follows. Could this be simplified through use of ThreadLocal, and would it retain the same properties as the named data slots? public static void SetSliceName(string slice) { System.Threading.Thread.SetData(System.Threading.Thread.GetNamedDataSlot(SliceVariable), slice); } public static string GetSliceName(bool errorIfNotFound) { var slice = System.Threading.Thread.GetData(System.Threading.Thread.GetNamedDataSlot(SliceVariable)) as string; if (errorIfNotFound && string.IsNullOrEmpty(slice)) {throw new ConfigurationErrorsException("Server slice name not configured.");} return slice; }

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  • virtual memory commited

    - by vinu
    After a server bounce happens, and after around 40-45 days time period, we receive continuous “Committed Virtual Memory” alerts which indicates the usage of swap space in the magnitude of 4GB This also causes the application to perform very slowly and experience a number of stalled transactions. Server Setup: 4 Tomcat Servers (version 7.0.22) that are load balanced (not clustered) by 2 Apache Servers. And the Apache servers themselves supply static content and routing to these 4 tomcat servers. Java Runtime Version: java version "1.6.0_30" Java(TM) SE Runtime Environment (build 1.6.0_30-b12) Java HotSpot(TM) 64-Bit Server VM (build 20.5-b03, mixed mode Memory Startup Parameters: MEMORY_OPTIONS="-Xms1024m -Xmx1024m -Xss192k -XX:MaxGCPauseMillis=500 -XX:+HeapDumpOnOutOfMemoryError -XX:MaxPermSize=256m -XX:+CMSClassUnloadingEnabled" Monitoring – Wily monitoring is available in all the production servers that monitors key server parameters and sends out configurable alert emails based on pre defined settings. Note: Each of the servers also has two other separate tomcat domains that run different applications Investigated area: There is no Heap Memory Leak and the GC is running fine without any issues over any period of time The current busy thread count corresponds directly to the application usage – weekends and nights have lesser no. of threads compared to business hours ThreadLocal uses a WeakReference internally. If the ThreadLocal is not strongly referenced, it will be garbage-collected, even though various threads have values stored via that ThreadLocal. Additionally, ThreadLocal values are actually stored in the Thread; if a thread dies, all of the values associated with that thread through a ThreadLocal are collected. If you have a ThreadLocal as a final class member, that's a strong reference, and it cannot be collected until the class is unloaded. But this is how any class member works, and isn't considered a memory leak. The cited problem only comes into play when the value stored in a ThreadLocal strongly references that ThreadLocal—sort of a circular reference. In this case, the value (a SimpleDateFormat), has no backwards reference to the ThreadLocal. There's no memory leak in this code. Can anyone please let me know what could be the cause of this and what to be monitored?

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  • Good way to make Authentication and Authorization information available between application layers

    - by DutrowLLC
    I have a web application running on Google App Engine (GAE) for JAVA. I'm authenticating the client at the Servlet layer but would like to make the client information available to my business and data layers without having to pass the client object through the arguments of every single function. I'm considering setting up a "session" type object using ThreadLocal. That way any function can just say something like: CurrentUser.getRoles(); Is this a good way to do this or is there something else that is a more accepted solution? Thanks!

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  • memory leak error when using an iterator

    - by Adnane Jaafari
    please i'm having this error if any one can explain it : while using an iterator in my methode public void createDemandeP() { if (demandep.getDateDebut().after(demandep.getDateFin())) { FacesContext .getCurrentInstance() .addMessage( null, new FacesMessage(FacesMessage.SEVERITY_WARN, "Attention aux dates", "la date de debut doit être avant la date de fin!")); } else if (demandep.getDateDebut().before(demandep.getDateFin())) { List<DemandeP> list = new ArrayList<DemandeP>(); list.addAll(chaletService.getChaletBylibelle(chaletChoisi).get(0) .getListDemandesP()); Iterator<DemandeP> it = list.iterator(); DemandeP d = it.next(); while (it.hasNext()) { if ((d.getDateDebut().compareTo(demandep.getDateDebut()) == 0) || (d.getDateFin().compareTo(demandep.getDateDebut()) == 0) || (d.getDateFin().compareTo(demandep.getDateFin()) == 0) || (d.getDateDebut().compareTo(demandep.getDateDebut()) == 0) || (d.getDateDebut().before(demandep.getDateDebut()) && d .getDateFin().after(demandep.getDateFin())) || (d.getDateDebut().before(demandep.getDateFin()) && d .getDateDebut().after(demandep.getDateDebut())) || (d.getDateFin().after(demandep.getDateDebut()) && d .getDateFin().before(demandep.getDateFin()))) { FacesContext.getCurrentInstance().getMessageList().clear(); FacesContext .getCurrentInstance() .addMessage( null, new FacesMessage( FacesMessage.SEVERITY_FATAL, "Periode Ou chalet indisponicle ", "Veillez choisir une autre marge de date !")); } } } else { demandep.setEtat("En traitement"); DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy"); Date date = new Date(); try { demandep.setDateDemande(dateFormat.parse(dateFormat .format(date))); } catch (ParseException e) { System.out.println("errooor date"); e.printStackTrace(); } nameUser = auth.getName(); // System.out.println(nameUser); adherent = utilisateurService.findAdherentByNom(nameUser).get(0); demandep.setUtilisateur(adherent); // System.out.println(chaletService.getChaletBylibelle(chaletChoisi).get(0).getLibelle()); demandep.setChalet(chaletService.getChaletBylibelle(chaletChoisi) .get(0)); demandep.setNouvelleDemande(true); demandePService.ajouterDemandeP(demandep); } } oct. 23, 2013 7:19:30 PM org.apache.catalina.core.StandardContext reload INFO: Le rechargement du contexte [/ONICLFINAL] a démarré oct. 23, 2013 7:19:30 PM org.apache.catalina.core.StandardWrapper unload INFO: Waiting for 1 instance(s) to be deallocated oct. 23, 2013 7:19:31 PM org.apache.catalina.core.StandardWrapper unload INFO: Waiting for 1 instance(s) to be deallocated oct. 23, 2013 7:19:32 PM org.apache.catalina.core.StandardWrapper unload INFO: Waiting for 1 instance(s) to be deallocated oct. 23, 2013 7:19:32 PM org.apache.catalina.core.ApplicationContext log INFO: Closing Spring root WebApplicationContext oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc SEVERE: The web application [/ONICLFINAL] registered the JDBC driver [com.mysql.jdbc.Driver] b but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: The web application [/ONICLFINAL] appears to have started a thread named [MySQL Statement Cancellation Timer] but has failed to stop it. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SE VERE: The web application [/ONICLFINAL] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Hibernate Sessions registered for deferred close]) and a value of type [java.util.HashMap] (value [{org.hibernate.impl.SessionFactoryImpl@f6e256=[SessionImpl(PersistenceContext[entityKeys=[EntityKey[bo.DemandeP#1], EntityKey[bo.Utilisateur#3], EntityKey[bo.Chalet#1], EntityKey[bo.Role#2], EntityKey[bo.DemandeP#2]],collectionKeys=[CollectionKey[bo.Role.ListeUsers#2], CollectionKey[bo.Chalet.listPeriodes#1], CollectionKey[bo.Utilisateur.demandes#3], CollectionKey[bo.Utilisateur.demandesP#3], CollectionKey[bo.Chalet.listDemandesP#1]]];ActionQueue[insertions=[] updates=[] deletions=[] collectionCreations=[] collectionRemovals=[] collectionUpdates=[]])]}]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Request attributes]) and a value of type [org.springframework.web.context.request.ServletRequestAttributes] (value [org.apache.catalina.connector.RequestFacade@17f3488]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@51f78b]) and a value of type [org.springframework.security.core.context.SecurityContextImpl] (value [org.springframework.security.core.context.SecurityContextImpl@8e463c8b: Authentication: org.springframework.security.authentication.UsernamePasswordAuthenticationToken@8e463c8b: Principal: org.springframework.security.core.userdetails.User@311aa119: Username: maatouf; Password: [PROTECTED]; Enabled: true; AccountNonExpired: true; credentialsNonExpired: true; AccountNonLocked: true; Granted Authorities: ROLE_ADHER; Credentials: [PROTECTED]; Authenticated: true; Details: org.springframework.security.web.authentication.WebAuthenticationDetails@ffff4c9c: RemoteIpAddress: 0:0:0:0:0:0:0:1; SessionId: 14CD5D4E8E0E3AEB0367AB7115038FED; Granted Authorities: ROLE_ADHER]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@152e9b7]) and a value of type [net.sf.cglib.proxy.Callback[]] (value [[Lnet.sf.cglib.proxy.Callback;@6e1f4c]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [javax.faces.context.FacesContext$1] (value [javax.faces.context.FacesContext$1@9ecc6d]) and a value of type [com.sun.faces.context.FacesContextImpl] (value [com.sun.faces.context.FacesContextImpl@1c8bbed]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@1a9e75f]) and a value of type [com.sun.faces.context.FacesContextImpl] (value [com.sun.faces.context.FacesContextImpl@1c8bbed]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Locale context]) and a value of type [org.springframework.context.i18n.SimpleLocaleContext] (value [fr_FR]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:32 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: The web application [/ONICLFINAL] created a ThreadLocal with key of type [com.sun.faces.application.ApplicationAssociate$1] (value [com.sun.faces.application.ApplicationAssociate$1@195266b]) and a value of type [com.sun.faces.application.ApplicationAssociate] (value [com.sun.faces.application.ApplicationAssociate@10d595c]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak. oct. 23, 2013 7:19:33 PM org.apache.catalina.loader.WebappClassLoader validateJarFile INFO: validateJarFile(D:\newWorkSpace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\ONICLF INAL\WEB-INF\lib\servlet-api-2.5.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class oct. 23, 2013 7:19:33 PM org.apache.catalina.core.ApplicationContext log

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  • Hibernate save() and transaction rollback

    - by Marco
    Hi, In Hibernate when i save() an object in a transaction, and then i rollback it, the saved object still remains in the DB. It's strange because this issue doesn't happen with the update() or delete() method, just with save(). Here is the code i'm using: DbEntity dbEntity = getDbEntity(); HibernateUtil.beginTransaction(); Session session = HibernateUtil.getCurrentSession(); session.save(dbEntity); HibernateUtil.rollbackTransaction(); And here is the HibernateUtil class (just the involved functions, i guarantee the getSessionFactory() method works well - there is an Interceptor handler, but it doesn't matter now): private static final ThreadLocal<Session> threadSession = new ThreadLocal<Session>(); private static final ThreadLocal<Transaction> threadTransaction = new ThreadLocal<Transaction>(); /** * Retrieves the current Session local to the thread. * <p/> * If no Session is open, opens a new Session for the running thread. * * @return Session */ public static Session getCurrentSession() throws HibernateException { Session s = (Session) threadSession.get(); try { if (s == null) { log.debug("Opening new Session for this thread."); if (getInterceptor() != null) { log.debug("Using interceptor: " + getInterceptor().getClass()); s = getSessionFactory().openSession(getInterceptor()); } else { s = getSessionFactory().openSession(); } threadSession.set(s); } } catch (HibernateException ex) { throw new HibernateException(ex); } return s; } /** * Start a new database transaction. */ public static void beginTransaction() throws HibernateException { Transaction tx = (Transaction) threadTransaction.get(); try { if (tx == null) { log.debug("Starting new database transaction in this thread."); tx = getCurrentSession().beginTransaction(); threadTransaction.set(tx); } } catch (HibernateException ex) { throw new HibernateException(ex); } } /** * Rollback the database transaction. */ public static void rollbackTransaction() throws HibernateException { Transaction tx = (Transaction) threadTransaction.get(); try { threadTransaction.set(null); if ( tx != null && !tx.wasCommitted() && !tx.wasRolledBack() ) { log.debug("Tyring to rollback database transaction of this thread."); tx.rollback(); } } catch (HibernateException ex) { throw new HibernateException(ex); } finally { closeSession(); } } Thanks

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  • How to make safe frequent DataSource switches for AbstractRoutingDataSource?

    - by serg555
    I implemented Dynamic DataSource Routing for Spring+Hibernate according to this article. I have several databases with same structure and I need to select which db will run each specific query. Everything works fine on localhost, but I am worrying about how this will hold up in real web site environment. They are using some static context holder to determine which datasource to use: public class CustomerContextHolder { private static final ThreadLocal<CustomerType> contextHolder = new ThreadLocal<CustomerType>(); public static void setCustomerType(CustomerType customerType) { Assert.notNull(customerType, "customerType cannot be null"); contextHolder.set(customerType); } public static CustomerType getCustomerType() { return (CustomerType) contextHolder.get(); } public static void clearCustomerType() { contextHolder.remove(); } } It is wrapped inside some ThreadLocal container, but what exactly does that mean? What will happen when two web requests call this piece of code in parallel: CustomerContextHolder.setCustomerType(CustomerType.GOLD); //<another user will switch customer type here to CustomerType.SILVER in another request> List<Item> goldItems = catalog.getItems(); Is every web request wrapped into its own thread in Spring MVC? Will CustomerContextHolder.setCustomerType() changes be visible to other web users? My controllers have synchronizeOnSession=true. How to make sure that nobody else will switch datasource until I run required query for current user? Thanks.

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  • SEVERE error in Eclipse Web application Startup

    - by lakshmanan
    I use tomcat. I am developing a web application using struts2, and I use eclipse as my IDE for development. I get this error Mar 7, 2010 7:38:42 PM org.apache.catalina.core.StandardContext filterStart SEVERE: Exception starting filter struts2 Unable to load bean: type:com.opensymphony.xwork2.ObjectFactory class:org.apache.struts2.spring.StrutsSpringObjectFactory - bean - jar:file:/C:/Documents%20and%20Settings/Lakshmanan/My%20Documents/My%20Dropbox/Final%20year%20project/Workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/projit1/WEB-INF/lib/struts2-spring-plugin-2.1.8.1.jar!/struts-plugin.xml:29:132 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:208) at org.apache.struts2.config.StrutsXmlConfigurationProvider.register(StrutsXmlConfigurationProvider.java:101) at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:131) at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52) at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:395) at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452) at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201) at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:295) at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:422) at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:115) at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3838) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4488) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardHost.start(StandardHost.java:722) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:593) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414) Caused by: java.lang.NoClassDefFoundError: com/opensymphony/xwork2/util/classloader/ReloadingClassLoader at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) at java.lang.Class.getDeclaredConstructors(Class.java:1836) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:198) ... 24 more Caused by: java.lang.ClassNotFoundException: com.opensymphony.xwork2.util.classloader.ReloadingClassLoader at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1484) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1329) ... 28 more Mar 7, 2010 7:38:42 PM org.apache.catalina.core.StandardContext start SEVERE: Error filterStart Mar 7, 2010 7:38:42 PM org.apache.catalina.core.StandardContext start SEVERE: Context [/projit1] startup failed due to previous errors Mar 7, 2010 7:38:42 PM org.apache.catalina.core.ApplicationContext log INFO: Closing Spring root WebApplicationContext Mar 7, 2010 7:38:42 PM org.springframework.context.support.AbstractApplicationContext doClose INFO: Closing Root WebApplicationContext: startup date [Sun Mar 07 19:38:41 GMT+05:30 2010]; root of context hierarchy Mar 7, 2010 7:38:42 PM org.springframework.beans.factory.support.DefaultSingletonBeanRegistry destroySingletons INFO: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@afae4a: defining beans [personCrud,companyCrud,projectCrud,discussionCrud]; root of factory hierarchy Mar 7, 2010 7:38:42 PM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc SEVERE: A web application registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered. Mar 7, 2010 7:38:42 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: A web application created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Prototype beans currently in creation]) and a value of type [null] (value [null]) but failed to remove it when the web application was stopped. To prevent a memory leak, the ThreadLocal has been forcibly removed. Mar 7, 2010 7:38:42 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap SEVERE: A web application created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [XML bean definition resources currently being loaded]) and a value of type [null] (value [null]) but failed to remove it when the web application was stopped. To prevent a memory leak, the ThreadLocal has been forcibly removed. I am confused . Please help me in rectifying this error.

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  • Inside the Concurrent Collections: ConcurrentBag

    - by Simon Cooper
    Unlike the other concurrent collections, ConcurrentBag does not really have a non-concurrent analogy. As stated in the MSDN documentation, ConcurrentBag is optimised for the situation where the same thread is both producing and consuming items from the collection. We'll see how this is the case as we take a closer look. Again, I recommend you have ConcurrentBag open in a decompiler for reference. Thread Statics ConcurrentBag makes heavy use of thread statics - static variables marked with ThreadStaticAttribute. This is a special attribute that instructs the CLR to scope any values assigned to or read from the variable to the executing thread, not globally within the AppDomain. This means that if two different threads assign two different values to the same thread static variable, one value will not overwrite the other, and each thread will see the value they assigned to the variable, separately to any other thread. This is a very useful function that allows for ConcurrentBag's concurrency properties. You can think of a thread static variable: [ThreadStatic] private static int m_Value; as doing the same as: private static Dictionary<Thread, int> m_Values; where the executing thread's identity is used to automatically set and retrieve the corresponding value in the dictionary. In .NET 4, this usage of ThreadStaticAttribute is encapsulated in the ThreadLocal class. Lists of lists ConcurrentBag, at its core, operates as a linked list of linked lists: Each outer list node is an instance of ThreadLocalList, and each inner list node is an instance of Node. Each outer ThreadLocalList is owned by a particular thread, accessible through the thread local m_locals variable: private ThreadLocal<ThreadLocalList<T>> m_locals It is important to note that, although the m_locals variable is thread-local, that only applies to accesses through that variable. The objects referenced by the thread (each instance of the ThreadLocalList object) are normal heap objects that are not specific to any thread. Thinking back to the Dictionary analogy above, if each value stored in the dictionary could be accessed by other means, then any thread could access the value belonging to other threads using that mechanism. Only reads and writes to the variable defined as thread-local are re-routed by the CLR according to the executing thread's identity. So, although m_locals is defined as thread-local, the m_headList, m_nextList and m_tailList variables aren't. This means that any thread can access all the thread local lists in the collection by doing a linear search through the outer linked list defined by these variables. Adding items So, onto the collection operations. First, adding items. This one's pretty simple. If the current thread doesn't already own an instance of ThreadLocalList, then one is created (or, if there are lists owned by threads that have stopped, it takes control of one of those). Then the item is added to the head of that thread's list. That's it. Don't worry, it'll get more complicated when we account for the other operations on the list! Taking & Peeking items This is where it gets tricky. If the current thread's list has items in it, then it peeks or removes the head item (not the tail item) from the local list and returns that. However, if the local list is empty, it has to go and steal another item from another list, belonging to a different thread. It iterates through all the thread local lists in the collection using the m_headList and m_nextList variables until it finds one that has items in it, and it steals one item from that list. Up to this point, the two threads had been operating completely independently. To steal an item from another thread's list, the stealing thread has to do it in such a way as to not step on the owning thread's toes. Recall how adding and removing items both operate on the head of the thread's linked list? That gives us an easy way out - a thread trying to steal items from another thread can pop in round the back of another thread's list using the m_tail variable, and steal an item from the back without the owning thread knowing anything about it. The owning thread can carry on completely independently, unaware that one of its items has been nicked. However, this only works when there are at least 3 items in the list, as that guarantees there will be at least one node between the owning thread performing operations on the list head and the thread stealing items from the tail - there's no chance of the two threads operating on the same node at the same time and causing a race condition. If there's less than three items in the list, then there does need to be some synchronization between the two threads. In this case, the lock on the ThreadLocalList object is used to mediate access to a thread's list when there's the possibility of contention. Thread synchronization In ConcurrentBag, this is done using several mechanisms: Operations performed by the owner thread only take out the lock when there are less than three items in the collection. With three or greater items, there won't be any conflict with a stealing thread operating on the tail of the list. If a lock isn't taken out, the owning thread sets the list's m_currentOp variable to a non-zero value for the duration of the operation. This indicates to all other threads that there is a non-locked operation currently occuring on that list. The stealing thread always takes out the lock, to prevent two threads trying to steal from the same list at the same time. After taking out the lock, the stealing thread spinwaits until m_currentOp has been set to zero before actually performing the steal. This ensures there won't be a conflict with the owning thread when the number of items in the list is on the 2-3 item borderline. If any add or remove operations are started in the meantime, and the list is below 3 items, those operations try to take out the list's lock and are blocked until the stealing thread has finished. This allows a thread to steal an item from another thread's list without corrupting it. What about synchronization in the collection as a whole? Collection synchronization Any thread that operates on the collection's global structure (accessing anything outside the thread local lists) has to take out the collection's global lock - m_globalListsLock. This single lock is sufficient when adding a new thread local list, as the items inside each thread's list are unaffected. However, what about operations (such as Count or ToArray) that need to access every item in the collection? In order to ensure a consistent view, all operations on the collection are stopped while the count or ToArray is performed. This is done by freezing the bag at the start, performing the global operation, and unfreezing at the end: The global lock is taken out, to prevent structural alterations to the collection. m_needSync is set to true. This notifies all the threads that they need to take out their list's lock irregardless of what operation they're doing. All the list locks are taken out in order. This blocks all locking operations on the lists. The freezing thread waits for all current lockless operations to finish by spinwaiting on each m_currentOp field. The global operation can then be performed while the bag is frozen, but no other operations can take place at the same time, as all other threads are blocked on a list's lock. Then, once the global operation has finished, the locks are released, m_needSync is unset, and normal concurrent operation resumes. Concurrent principles That's the essence of how ConcurrentBag operates. Each thread operates independently on its own local list, except when they have to steal items from another list. When stealing, only the stealing thread is forced to take out the lock; the owning thread only has to when there is the possibility of contention. And a global lock controls accesses to the structure of the collection outside the thread lists. Operations affecting the entire collection take out all locks in the collection to freeze the contents at a single point in time. So, what principles can we extract here? Threads operate independently Thread-static variables and ThreadLocal makes this easy. Threads operate entirely concurrently on their own structures; only when they need to grab data from another thread is there any thread contention. Minimised lock-taking Even when two threads need to operate on the same data structures (one thread stealing from another), they do so in such a way such that the probability of actually blocking on a lock is minimised; the owning thread always operates on the head of the list, and the stealing thread always operates on the tail. Management of lockless operations Any operations that don't take out a lock still have a 'hook' to force them to lock when necessary. This allows all operations on the collection to be stopped temporarily while a global snapshot is taken. Hopefully, such operations will be short-lived and infrequent. That's all the concurrent collections covered. I hope you've found it as informative and interesting as I have. Next, I'll be taking a closer look at ThreadLocal, which I came across while analyzing ConcurrentBag. As you'll see, the operation of this class deserves a much closer look.

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  • Spring scheduler shutdown error

    - by Alex
    During development a SPRING based scheduler in a tomcat container, I always get this logoutput at undeploy webapp or shutdown server: Apr 28, 2010 4:21:33 PM org.apache.catalina.core.StandardService stop INFO: Stopping service Catalina Apr 28, 2010 4:21:33 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: A web application appears to have started a thread named [org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-1] but has failed to stop it. This is very likely to create a memory leak. Apr 28, 2010 4:21:33 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: A web application appears to have started a thread named [org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-2] but has failed to stop it. This is very likely to create a memory leak. Apr 28, 2010 4:21:33 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: A web application appears to have started a thread named [org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-3] but has failed to stop it. This is very likely to create a memory leak. Apr 28, 2010 4:21:33 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: A web application appears to have started a thread named [org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-4] but has failed to stop it. This is very likely to create a memory leak. Apr 28, 2010 4:21:33 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads SEVERE: A web application appears to have started a thread named [org.springframework.scheduling.quartz.SchedulerFactoryBean#0_Worker-5] but has failed to stop it. This is very likely to create a memory leak. . . . SEVERE: A web application created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Prototype beans currently in creation]) and a value of type [null] (value [null]) but failed to remove it when the web application was stopped. To prevent a memory leak, the ThreadLocal has been forcibly removed. Apr 28, 2010 4:21:34 PM org.apache.coyote.http11.Http11Protocol destroy INFO: Stopping Coyote HTTP/1.1 on http-8606 How can I fix this?

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  • How do you create a non-Thread-based Guice custom Scope?

    - by Russ
    It seems that all Guice's out-of-the-box Scope implementations are inherently Thread-based (or ignore Threads entirely): Scopes.SINGLETON and Scopes.NO_SCOPE ignore Threads and are the edge cases: global scope and no scope. ServletScopes.REQUEST and ServletScopes.SESSION ultimately depend on retrieving scoped objects from a ThreadLocal<Context>. The retrieved Context holds a reference to the HttpServletRequest that holds a reference to the scoped objects stored as named attributes (where name is derived from com.google.inject.Key). Class SimpleScope from the custom scope Guice wiki also provides a per-Thread implementation using a ThreadLocal<Map<Key<?>, Object>> member variable. With that preamble, my question is this: how does one go about creating a non-Thread-based Scope? It seems that something that I can use to look up a Map<Key<?>, Object> is missing, as the only things passed in to Scope.scope() are a Key<T> and a Provider<T>. Thanks in advance for your time.

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  • How can I inject multiple repositories in a NServicebus message handler?

    - by Paco
    I use the following: public interface IRepository<T> { void Add(T entity); } public class Repository<T> { private readonly ISession session; public Repository(ISession session) { this.session = session; } public void Add(T entity) { session.Save(entity); } } public class SomeHandler : IHandleMessages<SomeMessage> { private readonly IRepository<EntityA> aRepository; private readonly IRepository<EntityB> bRepository; public SomeHandler(IRepository<EntityA> aRepository, IRepository<EntityB> bRepository) { this.aRepository = aRepository; this.bRepository = bRepository; } public void Handle(SomeMessage message) { aRepository.Add(new A(message.Property); bRepository.Add(new B(message.Property); } } public class MessageEndPoint : IConfigureThisEndpoint, AsA_Server, IWantCustomInitialization { public void Init() { ObjectFactory.Configure(config => { config.For<ISession>() .CacheBy(InstanceScope.ThreadLocal) .TheDefault.Is.ConstructedBy(ctx => ctx.GetInstance<ISessionFactory>().OpenSession()); config.ForRequestedType(typeof(IRepository<>)) .TheDefaultIsConcreteType(typeof(Repository<>)); } } My problem with the threadlocal storage is, is that the same session is used during the whole application thread. I discovered this when I saw the first level cache wasn't cleared. What I want is using a new session instance, before each call to IHandleMessages<.Handle. How can I do this with structuremap? Do I have to create a message module?

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  • Turning a JSON list into a POJO

    - by Josh L
    I'm having trouble getting this bit of JSON into a POJO. I'm using Jackson configured like this: protected ThreadLocal<ObjectMapper> jparser = new ThreadLocal<ObjectMapper>(); public void receive(Object object) { try { if (object instanceof String && ((String)object).length() != 0) { ObjectDefinition t = null ; if (parserChoice==0) { if (jparser.get()==null) { jparser.set(new ObjectMapper()); } t = jparser.get().readValue((String)object, ObjectDefinition.class); } Object key = t.getKey(); if (key == null) return; transaction.put(key,t); } } catch (Exception e) { e.printStackTrace(); } } Here's the JSON that needs to be turned into a POJO: { "id":"exampleID1", "entities":{ "tags":[ { "text":"textexample1", "indices":[ 2, 14 ] }, { "text":"textexample2", "indices":[ 31, 36 ] }, { "text":"textexample3", "indices":[ 37, 43 ] } ] } And lastly, here's what I currently have for the java class: protected Entities entities; @JsonIgnoreProperties(ignoreUnknown = true) protected class Entities { public Entities() {} protected Tags tags; @JsonIgnoreProperties(ignoreUnknown = true) protected class Tags { public Tags() {} protected String text; public String getText() { return text; } public void setText(String text) { this.text = text; } }; public Tags getTags() { return tags; } public void setTags(Tags tags) { this.tags = tags; } }; //Getters & Setters ... I've been able to translate the more simple objects into a POJO, but the list has me stumped. Any help is appreciated. Thanks!

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  • Optimizing processing and management of large Java data arrays

    - by mikera
    I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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  • Cannot make a static reference to the non-static type MyRunnable

    - by kaiwii ho
    Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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  • Java Generics error when implementing Hibernate message interpolator

    - by Jayaprakash
    Framework: Spring, Hibernate. O/S: Windows I am trying to implement hibernate's Custom message interpolator following the direction of this Link. When implementing the below class, it gives an error "Cannot make a static reference to the non-static type Locale". public class ClientLocaleThreadLocal<Locale> { private static ThreadLocal tLocal = new ThreadLocal(); public static void set(Locale locale) { tLocal.set(locale); } public static Locale get() { return tLocal.get(); } public static void remove() { tLocal.remove(); } } As I do not know generics enough, not sure how is being used by TimeFilter class below and the purpose of definition in the above class. public class TimerFilter implements Filter { public void destroy() { } public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException { try { ClientLocaleThreadLocal.set(req.getLocale()); filterChain.doFilter(req, res); }finally { ClientLocaleThreadLocal.remove(); } } public void init(FilterConfig arg0) throws ServletException { } } Will doing the following be okay? Change static method/field in ClientLocaleThreadLocal to non-static method/fields In TimeFilter, set locale by instantiating new object as below. new ClientLocaleThreadLocal().set(req.getLocale()) Thanks for your help in advance

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