Hibernate在多线程应用程序中随机抛出“org.Hibernate.exception.jdbcConnectionException：不能打开连接”

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();
}
}

有时，当使用这些mehtods之一时，我会重复出现此错误：

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

注意，我使用的是Heroku数据库(ClearDB，MySQL)，当我使用本地数据库时，我不能重现这个错误。

Answer 1

您已经实现了双重检查锁定模式。为了使其正常工作，必须使instance_session_factory变量volatile。

注意，这可能是也可能不是异常的原因，但它肯定是代码中的bug。

更新：

您可能只是遇到了池连接超时的情况。您可能希望尝试启用C3P0的空闲连接检查（类似于“idleConnectionTestPeriod=300”）。