c3p0创建的连接数多于配置中指定的数量

Question

我的应用程序使用的是Hibernate 4.1.7和c3p0 0.9.1.

我已将我的应用程序的hibernate.cfg.xml文件中的c3p0.max_size属性设置为50,但创建的JDBC连接数已超过该值.此外,我没有删除非活动/空闲连接,因为我在Hibernate配置中也已指定.这是我的配置中的一个剪辑:

<property name="c3p0.acquire_increment">1</property>
<property name="c3p0.autoCommitOnClose">false</property>
<property name="c3p0.max_size">50</property>
<property name="c3p0.min_size">1</property>
<property name="c3p0.numHelperThreads">1</property>
<property name="c3p0.maxIdleTime">30</property> 
<property name="c3p0.maxIdleTimeExcessConnections">20</property>
<property name="c3p0.maxConnectionAge">45</property>

我明确地在我的代码中的finally块中关闭我的会话和会话工厂.这是我用来创建SessionFactory实例的类:

package ics.sis.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

import ics.global.runtime.Environment;
import ics.util.properties.PropertiesISUWrapper;

public class HibernateSessionFactory {
    private static SessionFactory sessionFactory;
    private static ServiceRegistry serviceRegistry;
    private static final PropertiesISUWrapper ISU_PROPERTIES = new PropertiesISUWrapper(Environment.getName(),"VzAppIntegration"); 

    public static SessionFactory create() {
        Configuration configuration = new Configuration();
        configuration.configure();

        configuration.setProperty("hibernate.connection.url", ISU_PROPERTIES.getUrl());
        configuration.setProperty("hibernate.connection.password", ISU_PROPERTIES.getPassword());

        serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();        
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        return sessionFactory;
    }

}

这是执行数据库事务的主要方法之一:

public static int insert(int aidm, String termCode, String wappCode) throws SQLException, ClassNotFoundException {      
        // Initialize session and transaction
        SessionFactory sessionFactory = HibernateSessionFactory.create();
        Session session = sessionFactory.openSession();
        Transaction tx = null;
        int applSeqno = 0;
        Stvwapp wapp = null;

        try {
            tx = session.beginTransaction();

            applSeqno = generateApplSeqNo(session, aidm);
            SarheadId sarheadIdDao = new SarheadId();
            sarheadIdDao.setSarheadAidm(aidm);
            sarheadIdDao.setSarheadApplSeqno((short)applSeqno);

            // Find STVWAPP row by WAPP code
            Query query = session.getNamedQuery("findStvwappByWappCode"); 
            query.setString("wappCode", wappCode);

            if (query.list().size() == 0) {
                throw new RuntimeException("Invalid WAPP code specified: " + wappCode);
            } else {
                wapp = (Stvwapp) query.list().get(0);
            }

            Sarhead sarheadDao = new Sarhead();
            sarheadDao.setId(sarheadIdDao);
            sarheadDao.setSarheadActivityDate(new java.sql.Timestamp(System.currentTimeMillis()));
            sarheadDao.setSarheadAddDate(new java.sql.Timestamp(System.currentTimeMillis()));
            sarheadDao.setSarheadAplsCode("WEB");
            sarheadDao.setSarheadApplAcceptInd("N");
            sarheadDao.setSarheadApplCompInd("N");
            sarheadDao.setSarheadApplStatusInd("N");
            sarheadDao.setSarheadPersStatusInd("N");
            sarheadDao.setSarheadProcessInd("N");
            sarheadDao.setSarheadTermCodeEntry(termCode);
            sarheadDao.setStvwapp(wapp);

            session.save(sarheadDao);
        } finally {
            tx.commit();
            session.close();
            sessionFactory.close(); 
        }

        return applSeqno;
    }

更新

我将c3p0的日志级别更改为DEBUG以获得更详细的连接池日志记录,并且我看到它每隔3或4秒检查过期连接.另外,我看到记录了以下行,对我来说,看起来池中总共有两个连接.但是,在Toad中,我正在监视打开的JDBC连接总数,它显示为6.所以我试图弄清楚为什么这些数字之间存在差异.

[环境:DEVL] [] - 2012-12-06 12:14:07 DEBUG BasicResourcePool:1644 - trace com.mchange.v2.resourcepool.BasicResourcePool@7f1d11b9 [managed:1,unused:1,excluded:0](例如com.mchange.v2.c3p0.impl.NewPooledConnection@7b3f1264)

Answer 1

你这么说:

我已将我的应用程序的hibernate.cfg.xml文件中的c3p0.max_size属性设置为50,但创建的JDBC连接数已超过该值.

发生这种情况是因为在您的insert方法中您正在调用create()方法.每次在您的create()方法中,您都构建一个全新的sessionFactory,如下所示:

 configuration.buildSessionFactory(serviceRegistry);

在那种方法中你也关闭了sessionFactory.创建和关闭sessionFactory实例都是极其昂贵的操作(您可以在此处查看关闭方法).

最重要的是,当您的应用程序在多个线程中一次提供多个请求时,每个线程都会创建自己的sessionFactory(每个创建自己的池).因此,在您的系统中存在多个sessionFactory和Connection池.虽然您应该在应用程序的生命周期内只创建一次.因此,当存在多个池副本时,所有池的连接总数可能超过您为一个池配置的最大限制.

我建议你HibernateSessionFactory像下面一样重写你的课程:

public class HibernateSessionFactory {
    private static SessionFactory sessionFactory = HibernateSessionFactory.create();
    private static ServiceRegistry serviceRegistry;
    private static final PropertiesISUWrapper ISU_PROPERTIES = new PropertiesISUWrapper(Environment.getName(),"VzAppIntegration"); 

    private static SessionFactory create() {
        Configuration configuration = new Configuration();
        configuration.configure();

        configuration.setProperty("hibernate.connection.url", ISU_PROPERTIES.getUrl());
        configuration.setProperty("hibernate.connection.password", ISU_PROPERTIES.getPassword());

        serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();        
        return configuration.buildSessionFactory(serviceRegistry);

    }

    public static SessionFactory getSessionFactory(){
       return sessionFactory;
    }

}

而在insert()方法而不是呼叫HibernateSessionFactory.create(),只需要打电话HibernateSessionFactory.getSessionFactory().