休眠拋出「org.hibernate.exception.JDBCConnectionException：無法打開連接」隨機在多線程應用程序

Question

public class HibernateUtil { 

private static SessionFactory INSTANCE_SESSION_FACTORY = null; 

public enum Common { 
    SUCCESS, ROLLBACK 
} 

private synchronized static void createSessionFactory() { 
    try { 
     if (INSTANCE_SESSION_FACTORY != null) { 
      return; 
     } 
     ResourceBundle rb = ResourceBundle.getBundle("application"); 
     Integer environment = Integer.valueOf(rb.getString("environment")); 

     Properties prop = new Properties(); 

     switch (environment) { 
     /* LOCAL */ 
     case 1: 
      prop.setProperty("hibernate.connection.driver_class", rb.getString("hibernate.driver.class.name")); 
      prop.setProperty("hibernate.connection.url", rb.getString("hibernate.db.uri")); 
      prop.setProperty("hibernate.connection.username", rb.getString("hibernate.db.username")); 
      prop.setProperty("hibernate.connection.password", rb.getString("hibernate.db.password")); 
      break; 
     default: 
      throw new ConfigurationException(environment == null ? "No environment added in application.properties" 
        : "Wrong environment added in application.properties"); 
     } 

     prop.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQLDialect"); 
     prop.setProperty("hibernate.show_sql", "true"); 
     prop.setProperty("hibernate.hbm2ddl.auto", "update"); 
     prop.setProperty("hibernate.current_session_context_class", "thread"); 
     prop.setProperty("hibernate.connection.pool_size", "100"); 

     prop.setProperty("hibernate.c3p0.minPoolSize", "5"); 
     prop.setProperty("hibernate.c3p0.maxPoolSize", "100"); 
     prop.setProperty("hibernate.c3p0.initialPoolSize", "10"); 
     prop.setProperty("hibernate.c3p0.timeout", "1800"); 
     prop.setProperty("hibernate.c3p0.max_statements=", "50"); 

     org.hibernate.cfg.Configuration config = new org.hibernate.cfg.Configuration().addProperties(prop) 
       .addAnnotatedClass(Account.class).addAnnotatedClass(InsynctiveProperty.class) 
     serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()) 
     .buildServiceRegistry(); 
     INSTANCE_SESSION_FACTORY = config.buildSessionFactory(serviceRegistry); 
    } catch (Throwable ex) { 
     System.err.println("Initial SessionFactory creation failed." + ex); 
     throw new ExceptionInInitializerError(ex); 
    } 
} 

public static SessionFactory getSessionFactory() { 
    if (INSTANCE_SESSION_FACTORY == null) { 
     createSessionFactory(); 
    } 
    return INSTANCE_SESSION_FACTORY; 
} 

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

public static Session openSession() { 
    return getSessionFactory().openSession(); 
} 

public static void closeCurrentSession() { 
    getSessionFactory().getCurrentSession().close(); 
} 

public synchronized static Object get(Class<?> clazz, Integer id) { 
    Session session = getCurrentSession(); 
    final Transaction transaction = session.beginTransaction(); 
    try { 
     Object obj = session.get(clazz, id); 
     transaction.commit(); 
     return obj; 
    } catch (RuntimeException ex) { 
     System.out.println(ex); 
     transaction.rollback(); 
     throw ex; 
    } finally { 

    } 
} 

public Common save(Object object) { 
    Session session = openCurrentSession(); 
    Transaction transaction = null; 
    Common result = null; 
    try { 
     transaction = openTransaction(session); 
     session.save(object); 
     transaction.commit(); 
     result = Common.SUCCESS; 
    } catch (Exception e) { 
     e.printStackTrace(); 
     if (transaction != null) { 
      transaction.rollback(); 
     } 
     result = Common.ROLLBACK; 
    } finally { 
     session.close(); 
    } 

    return result; 
} 

public Common update(Object object) { 
    Session session = openCurrentSession(); 
    Transaction transaction = null; 
    Common result; 

    try { 
     transaction = openTransaction(session); 
     session.update(object); 
     transaction.commit(); 
     result = Common.SUCCESS; 
    } catch (Exception e) { 
     e.printStackTrace(); 

     if (transaction != null) { 
      transaction.rollback(); 
     } 
     result = Common.ROLLBACK; 
    } finally { 
     session.close(); 
    } 
    return result; 
} 

public Session openCurrentSession() { 
    return getSessionFactory().openSession(); 
} 

public Transaction openTransaction(Session session) { 
    return session.beginTransaction(); 
} 
} 

有時，當使用這些mehtods之一，我recive這個錯誤：

org.hibernate.exception.JDBCConnectionException: Could not open connection

[org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:131), org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49), org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125), org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110), org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:304), org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:169), org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:67), org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:160), org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1396), sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method), sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62), sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43), java.lang.reflect.Method.invoke(Method.java:483), org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:352), com.sun.proxy.$Proxy66.beginTransaction(Unknown Source), insynctive.utils.HibernateUtil.get(HibernateUtil.java:123), insynctive.tests.TestMachine.tearUp(TestMachine.java:104), insynctive.tests.PersonFileTest.tearUp(PersonFileTest.java:52), sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method), sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62), sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43), java.lang.reflect.Method.invoke(Method.java:483), org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85), org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:517), org.testng.internal.Invoker.invokeConfigurations(Invoker.java:213), org.testng.internal.Invoker.invokeConfigurations(Invoker.java:140), org.testng.internal.TestMethodWorker.invokeBeforeClassMethods(TestMethodWorker.java:170), org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:104), org.testng.TestRunner.privateRun(TestRunner.java:771), org.testng.TestRunner.run(TestRunner.java:621), org.testng.SuiteRunner.runTest(SuiteRunner.java:357), org.testng.SuiteRunner.runSequentially(SuiteRunner.java:352), org.testng.SuiteRunner.privateRun(SuiteRunner.java:310), org.testng.SuiteRunner.run(SuiteRunner.java:259), org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52), org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86), org.testng.TestNG.runSuitesSequentially(TestNG.java:1199), org.testng.TestNG.runSuitesLocally(TestNG.java:1124), org.testng.TestNG.run(TestNG.java:1032), insynctive.runnable.RunnableTest.run(RunnableTest.java:15), java.lang.Thread.run(Thread.java:745)]

SQLStateConversionDelegate.java:131

else if (CONNECTION_CATEGORIES.contains(sqlStateClassCode)) { 
        return new JDBCConnectionException(message, sqlException, sql); 

，我需要重新啓動庫會話繼續工作..

任何想法發生了什麼？ 我的應用程序是一個多線程應用，我像扔6-10 線程。

注 我使用Heroku的DB（ClearDB MySQL的）當我用一個本地數據庫我不能重現此錯誤。

Answer 1

您已經實現了雙重檢查鎖定模式。爲了使其正常工作，您必須使INSTANCE_SESSION_FACTORY變量volatile。

筆記，可能會或可能不會是異常的原因，但肯定是在你的代碼中的bug。

UPDATE：

這是可能只運行到您的池連接超時的情況。你可能想嘗試啓用c3p0的空閒連接檢查（類似「idleConnectionTestPeriod = 300」）。