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karengsh
 Post subject: What's wrong with my Hibernate Utility class ?
PostPosted: Sat Dec 30, 2017 8:07 am 
Beginner
Beginner

Joined: Tue Aug 08, 2017 12:14 am
Posts: 44
Hi experts,

I got the below error and I suspected there is an error some where but I could not figure out why.

Initially, I got error in accessing tables metadata then I saw this Utility class as per

https://stackoverflow.com/questions/436 ... 6#43718626

and I copied it and the metadata error is gone but then the new error is :

Quote:
java.lang.NullPointerException
at util.HibernateUtil.getSession(HibernateUtil.java:40)
at Business.RegisterService.register(RegisterService.java:16)


Here's the class :

Code:
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;



public class HibernateUtil {
   
   private static StandardServiceRegistry registry;
     private static SessionFactory sessionFactory;

      public static SessionFactory getSessionFactory() {
           return buildSessionFactory();
      }

     public static SessionFactory buildSessionFactory() {
       if (sessionFactory == null) {
         try {
           registry = new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml").build();
           MetadataSources sources = new MetadataSources(registry);
           Metadata metadata = sources.getMetadataBuilder().build();
           sessionFactory = metadata.getSessionFactoryBuilder().build();
         } catch (Exception e) {
           e.printStackTrace();
           shutdown();
         }
       }
       return sessionFactory;
     }

   public static Session getSession() {
           Session hibernateSession = getSessionFactory().getCurrentSession();
           return hibernateSession;
         }

     public static void shutdown() {
       if (registry != null) {
         StandardServiceRegistryBuilder.destroy(registry);
       }
     }
   }


[code]
public class RegisterService {

   public boolean register(Tutor tutor){
   Session session = HibernateUtil.getSession(); // error here line 16
   if(isTutorExists(tutor)) return false;
   
   Transaction tx = null;
   try{
      tx = session.getTransaction();


<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.2.10.Final</version>
</dependency>

I really can't figure out what is wrong. Hope someone can let me know the reason.

Tks.
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vlad
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Sat Dec 30, 2017 10:32 am 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1628
Location: Romania
First, you don't need a BibernateUtil class. Just use Spring or Java EE and inject the SessionFactory or the EntityManager Factory.

Second, the getSessionFactory method is wrong, it should be like this:

Code:
public static synchronized SessionFactory getSessionFactory() {
    return sessionFactory != null ?
        sessionFactory :
        buildSessionFactory();
}


If you already have a SessionFactory, just reuse it and make sure that only one Thread can build a SessionFactory.
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karengsh
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Sun Dec 31, 2017 10:45 am 
Beginner
Beginner

Joined: Tue Aug 08, 2017 12:14 am
Posts: 44
vlad wrote:
First, you don't need a BibernateUtil class. Just use Spring or Java EE and inject the SessionFactory or the EntityManager Factory.

Second, the getSessionFactory method is wrong, it should be like this:

Code:
public static synchronized SessionFactory getSessionFactory() {
    return sessionFactory != null ?
        sessionFactory :
        buildSessionFactory();
}


If you already have a SessionFactory, just reuse it and make sure that only one Thread can build a SessionFactory.


Hi vlad,

After I changed the utility file, I am getting another 'funny' error -
Quote:
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'hi5s.subject' doesn't exist


But, the table exists in my database.

What do you think I should do in this case ?

Furthermore, I'd like to clarify if Tomcat can work with Java EE SessionFactory bean injection ? - Are you referring to EJB 3 ?
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vlad
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Sun Dec 31, 2017 6:55 pm 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1628
Location: Romania
Quote:
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'hi5s.subject' doesn't exist


Maybe the catalog hi5s was not set properly in Hibernate.

Quote:
Furthermore, I'd like to clarify if Tomcat can work with Java EE SessionFactory bean injection ? - Are you referring to EJB 3 ?


If you use Spring, then yes. If you don't use Spring, then you need something like TomEE.
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karengsh
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Thu Jan 04, 2018 11:32 am 
Beginner
Beginner

Joined: Tue Aug 08, 2017 12:14 am
Posts: 44
vlad wrote:
Quote:
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'hi5s.subject' doesn't exist


Maybe the catalog hi5s was not set properly in Hibernate.

Quote:
Furthermore, I'd like to clarify if Tomcat can work with Java EE SessionFactory bean injection ? - Are you referring to EJB 3 ?


If you use Spring, then yes. If you don't use Spring, then you need something like TomEE.


Hi vlad,

I think I want to keep things simple before I explore Spring cos you know my Java knowledge still needs improvement. If not for difficult in doing it via the JDBC way for the join table, I would not jump into Hibernate either. Please correct me if I am on the right track being like this.

For now, is it ok just to use SessionFactory from Hibernate to do the session transaction ?

Anyway, I keep getting the below error and I just can't resolve it and so I am here seeking your expertise again:

Code:
Jan 04, 2018 11:23:14 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=root, password=****}
Jan 04, 2018 11:23:14 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Jan 04, 2018 11:23:14 PM org.hibernate.engine.jdbc.connections.internal.PooledConnections <init>
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
Jan 04, 2018 11:23:14 PM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL55Dialect
Jan 04, 2018 11:23:21 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@4dfb86db] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
Jan 04, 2018 11:23:21 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 1146, SQLState: 42S02
Jan 04, 2018 11:23:21 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Table 'hi5s.subject' doesn't exist
Jan 04, 2018 11:23:21 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH10001008: Cleaning up connection pool [jdbc:mysql://localhost:3306/hi5s?useSSL=false]
Initial SessionFactory creation failed.org.hibernate.exception.SQLGrammarException: Error accessing tables metadata
Jan 04, 2018 11:23:21 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [controller.tutorController] in context with path [/Hi5S] threw exception [Servlet execution threw an exception] with root cause
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'hi5s.subject' doesn't exist
   at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
   at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
   at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
   at java.lang.reflect.Constructor.newInstance(Unknown Source)
   at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
   at com.mysql.jdbc.Util.getInstance(Util.java:408)
   at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:944)
   at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973)
   at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909)
   at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527)
   at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680)
   at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2480)
   at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2438)
   at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1381)
   at com.mysql.jdbc.DatabaseMetaData$2.forEach(DatabaseMetaData.java:2441)
   at com.mysql.jdbc.DatabaseMetaData$2.forEach(DatabaseMetaData.java:2339)
   at com.mysql.jdbc.IterateBlock.doForAll(IterateBlock.java:50)
   at com.mysql.jdbc.DatabaseMetaData.getColumns(DatabaseMetaData.java:2337)
   at org.hibernate.tool.schema.extract.internal.InformationExtractorJdbcDatabaseMetaDataImpl.populateTablesWithColumns(InformationExtractorJdbcDatabaseMetaDataImpl.java:350)
   at org.hibernate.tool.schema.extract.internal.InformationExtractorJdbcDatabaseMetaDataImpl.getTables(InformationExtractorJdbcDatabaseMetaDataImpl.java:337)
   at org.hibernate.tool.schema.extract.internal.DatabaseInformationImpl.getTablesInformation(DatabaseInformationImpl.java:120)
   at org.hibernate.tool.schema.internal.GroupedSchemaMigratorImpl.performTablesMigration(GroupedSchemaMigratorImpl.java:65)
   at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.performMigration(AbstractSchemaMigrator.java:203)
   at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.doMigration(AbstractSchemaMigrator.java:110)
   at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:183)
   at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:72)
   at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:309)
   at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:452)
   at util.HibernateUtil.buildSessionFactory(HibernateUtil.java:27)
   at util.HibernateUtil.<clinit>(HibernateUtil.java:16)
   at Business.RegisterService.register(RegisterService.java:16)
   at controller.tutorController.doPost(tutorController.java:79)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
   at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
   at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
   at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
   at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
   at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
   at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
   at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
   at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
   at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
   at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
   at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
   at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
   at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
   at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
   at java.lang.Thread.run(Unknown Source)


And here's my hibernate.cfg.xml :

Code:
<session-factory>

      <!-- SQL Dialect -->

      <property name="dialect">org.hibernate.dialect.MySQL55Dialect</property>
      <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
      <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hi5s?useSSL=false</property>
      <property name="hibernate.connection.username">root</property>
      <property name="hibernate.connection.password">password</property>

      <property name="transation.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
      <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>
      <!-- Disable the second-level cache -->
      <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
      <!-- Echo all executed SQL to stdout -->
      <property name="hibernate.show_sql">true</property>
      <property name="hibernate.id.new_generator_mappings">false</property>
      <!-- Upate is for table already there -->
      <property name="hibernate.hbm2ddl.auto">update</property>

      <!-- Enable Hibernate's automatic session context management -->
      <property name="hibernate.current_session_context_class">thread</property>

      <!-- Mention here all the model classes along with their package name -->
      <mapping class="model.User" />
      <mapping class="model.Tutor" />
      <mapping class="model.Subject" />
      
      </session-factory>

When you mentioned the catalog hi5s was not set properly in Hibernate. Are you referring to this cfg.xml file ? Cos everything is there.....
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vlad
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Thu Jan 04, 2018 11:49 am 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1628
Location: Romania
If you specified the table like that:

Code:
<class name = "Subject" table = "hi5s.subject">


in the entity mapping, try setting it to:

Code:
<class name = "Subject" table = "subject">
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karengsh
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Mon Jan 08, 2018 11:44 am 
Beginner
Beginner

Joined: Tue Aug 08, 2017 12:14 am
Posts: 44
vlad wrote:
First, you don't need a BibernateUtil class. Just use Spring or Java EE and inject the SessionFactory or the EntityManager Factory.

If you already have a SessionFactory, just reuse it and make sure that only one Thread can build a SessionFactory.

Hi vlad,

I'd like to clarify with you regarding your comment - only one Thread can build a SessionFactory.

How do I make sure that it is only one Thread cos I have insert every method in my logic class with a SessionFactory factory = HibernateUtil.getSessionFactory();

Session session = factory.openSession();
follows by beginTransaction...and the standard transaction.rollback follows by session.close().

So, I presume if my controller is to check one method follows by another, the session will open and close(1 thread), open and close( a new thread will start again).

But, it is not working at all. Is there something that I am missing here?


Cos run when I debug my app, I got the following error stack trace and it stays forever at many Daemon threads :
Quote:
Daemon Thread [http-nio-8080-exec-6] (Suspended)
Unsafe.park(boolean, long) line: not available [native method]
LockSupport.park(Object) line: not available
AbstractQueuedSynchronizer$ConditionObject.await() line: not available
TaskQueue(LinkedBlockingQueue<E>).take() line: not available
TaskQueue.take() line: 103
TaskQueue.take() line: 31
ThreadPoolExecutor(ThreadPoolExecutor).getTask() line: not available
ThreadPoolExecutor(ThreadPoolExecutor).runWorker(ThreadPoolExecutor$Worker) line: not available
ThreadPoolExecutor$Worker.run() line: not available
TaskThread$WrappingRunnable.run() line: 61
TaskThread(Thread).run() line: not available


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vlad
 Post subject: Re: What's wrong with my Hibernate Utility class ?
PostPosted: Mon Jan 08, 2018 12:42 pm 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1628
Location: Romania
Quote:
So, I presume if my controller is to check one method follows by another, the session will open and close(1 thread), open and close( a new thread will start again).


No. Just use synchronized for when you create the Sessionfactory, as I already mentioned.
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