java - How to make DAO thread safe JPA? -

i new jpa , java. understood how entitymanager , emf works littel bit. have jpautill entitymanager, using threadlocal variable, makes entitymanager thread safe. have dao in persisting new users when having 10 thousand thread accesses simultaneously.

i see following exception:

javax.persistence.persistenceexception: org.hibernate.sessionexception: session closed!         @ org.hibernate.ejb.abstractentitymanagerimpl.throwpersistenceexception(abstractentitymanagerimpl.java:614) 

here dao code

try{     entitymanager = jpautil.getentitymanager();     user.setarea(getarea());     user.setcity(getcity());     user.setpassword("xxxxx");     user.setemail_id(getemail_id());     user.setmobile_num(tempmobile_num);     user.setfirst_name(getfirst_name());     user.setsession_id("0");     user.setemail_verification_status("not verified");     user.setbalance(new bigdecimal(0.00));     if (!entitymanager.gettransaction().isactive()){         entitymanager.gettransaction().begin();     }     entitymanager.persist(user);     jpautil.commit(); } catch (exception e) {     logger.info(e);     e.printstacktrace(); } finally{     if(entitymanager.isopen())     jpautil.closeentitymanager(); } 

jpautil:

public class jpautil {      private static logger logger = logger.getlogger(jpautil.class);     private static entitymanager entitymanager = null;     private static final threadlocal<entitymanager> threadlocal;      private static entitymanagerfactory emf = null;      static {         try {             emf = persistence.createentitymanagerfactory("xyzdb");             threadlocal = new threadlocal<entitymanager>();         } catch (throwable ex) {             logger.info("jpautil exception", ex);             throw new exceptionininitializererror(ex);         }     }      public static entitymanager getentitymanager() {         try {             entitymanager = threadlocal.get();              if (entitymanager == null || !entitymanager.isopen()) {                  jpautil.entitymanager = emf.createentitymanager();                 threadlocal.set(entitymanager);              } else if (!emf.isopen()) {                 entitymanager = threadlocal.get();                 emf = persistence.createentitymanagerfactory("xyzdb");                 jpautil.entitymanager = emf.createentitymanager();                 threadlocal.set(entitymanager);             }         } catch (throwable ex) {             logger.info("jpautil exception", ex);             throw new exceptionininitializererror(ex);         }         return jpautil.entitymanager;     }      public static void closeentitymanager() {         entitymanager entitymanager = threadlocal.get();         if (entitymanager != null) {             entitymanager.close();             threadlocal.set(null);         }     }      public static void closeentitymanagerfactory() {         emf.close();     }      public static void commit() {         if (!entitymanager.gettransaction().isactive()) {             entitymanager.gettransaction().begin();         }         entitymanager.gettransaction().commit();     }      public static void rollback() {         if (!entitymanager.gettransaction().isactive()) {             entitymanager.gettransaction().begin();         }         entitymanager.gettransaction().rollback();     } } 

can please me understand issue , how resolve it?

remove static variable form jpautil:

private static entitymanager entitymanager = null; 

you still using static variable; didn't use threadlocal.

change getentitymanager this:

public static entitymanager getentitymanager() {     entitymanager entitymanager;     try {         entitymanager = threadlocal.get();          if (entitymanager == null || !entitymanager.isopen()) {             entitymanager = emf.createentitymanager();             threadlocal.set(entitymanager);          }     } catch (throwable ex) {         logger.info("jpautil exception", ex);         throw new exceptionininitializererror(ex);     }     return entitymanager; }