java - 似乎 Hibernate 超出了连接限制

Question

谁能帮我解决这个问题？我有一个 Tomcat 和简单的 JSF 应用程序:https://github.com/gooamoko/jsfbilling/ .当我在 Tomcat 上运行应用程序时，它运行正常，但在多次请求(例如 10 次快速刷新页面)后引发异常 can't open connection。我想，这很正常，但哪里错了？

在配置文件hibernate.cfg.xml中

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
        <property name="connection.driver_class">org.postgresql.Driver</property>
        <property name="connection.url">jdbc:postgresql://localhost:5432/netstat</property>
        <property name="connection.username">netstat</property>
        <property name="connection.password">netstat</property>

        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- configuration pool via c3p0 -->
        <property name="c3p0.min_size">5</property>
        <property name="c3p0.max_size">100</property>
        <property name="c3p0.max_statements">200</property>
        <property name="c3p0.timeout">600</property> <!-- seconds -->

        <property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
        <property name="current_session_context_class">thread</property>
        <property name="hibernate.show_sql">false</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <!-- Mapping classes -->
        <mapping class="ru.gooamoko.model.Group" />
        <mapping class="ru.gooamoko.model.Host" />
        <mapping class="ru.gooamoko.model.Traffic" />
        <mapping class="ru.gooamoko.model.DailyTraffic" />

    </session-factory>
</hibernate-configuration>

或者在 Java 类中

package ru.gooamoko.dao;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateProvider {
    private static SessionFactory factory;
    private static ServiceRegistry registry;

    public static SessionFactory getSessionFactory() {
        Configuration configuration = new Configuration();
        configuration.configure();
        registry = new StandardServiceRegistryBuilder().applySettings(
                configuration.getProperties()).build();
        factory = configuration.buildSessionFactory(registry);
        return factory;
    }

}


package ru.gooamoko.dao;

import org.hibernate.Session;
import org.hibernate.SessionFactory;

public class GenericDao {

    private SessionFactory factory;
    protected Session session;

    protected void begin() {
        session = factory.getCurrentSession();
        session.beginTransaction();
    }

    protected void commit() {
        if (session.isOpen()) {
            session.getTransaction().commit();
        }
    }

    protected void rollback() {
        if (session.isOpen()) {
            session.getTransaction().rollback();
        }
    }

    public GenericDao() {
        this.factory = HibernateProvider.getSessionFactory();
    }
}

在 tomcat 日志中我看到了这个

27-Aug-2014 15:06:24.559 WARNING [C3P0PooledConnectionPoolManager[identityToken->1hge12w9467h4hm1tfa5tj|3b40a97d]-HelperThread-#2] com.mchange.v2.resourcepool.BasicResourcePool.forceKillAcquires Having failed to acquire a resource, com.mchange.v2.resourcepool.BasicResourcePool@4df5a3a4 is interrupting all Threads waiting on a resource to check out. Will try again in response to new client requests.
27-Aug-2014 15:06:24.563 WARNING [C3P0PooledConnectionPoolManager[identityToken->1hge12w9467h4hm1tfa5tj|3b40a97d]-HelperThread-#2] com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@628977a2 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
 org.postgresql.util.PSQLException: ?????: ?????????? ????? ??????????? ??????????????? ??? ??????????? ????????????????? (?? ??? ??????????)
    at org.postgresql.core.v3.ConnectionFactoryImpl.readStartupMessages(ConnectionFactoryImpl.java:572)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:177)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:64)
    at org.postgresql.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:136)
    at org.postgresql.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:29)
    at org.postgresql.jdbc3g.AbstractJdbc3gConnection.<init>(AbstractJdbc3gConnection.java:21)
    at org.postgresql.jdbc4.AbstractJdbc4Connection.<init>(AbstractJdbc4Connection.java:31)
    at org.postgresql.jdbc4.Jdbc4Connection.<init>(Jdbc4Connection.java:24)
    at org.postgresql.Driver.makeConnection(Driver.java:393)
    at org.postgresql.Driver.connect(Driver.java:267)
    at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:146)
    at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195)
    at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
    at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
    at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
    at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
    at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
    at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)

我应该如何以及在何处更正关闭打开的连接？

谢谢你为我浪费你的时间。

Answer 1

我阅读了 Hibernate 文档并找到了 HibernateUtil 类的示例。在与我的 HibernateProvider 进行比较后，我发现，在我的 HibernateProvider 工厂中似乎是在每次调用 getSessionFactory() 时构建的。 HibernateProvider 的新版本是

package ru.gooamoko.dao;

import org.hibernate.HibernateException;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateProvider {

  private static final SessionFactory factory = buildFactory();

  public static SessionFactory getSessionFactory() {
    return factory;
  }

  private static SessionFactory buildFactory() {
    try {
      Configuration configuration = new Configuration();
      configuration.configure();
      ServiceRegistry registry = new StandardServiceRegistryBuilder().applySettings(
          configuration.getProperties()).build();
      return configuration.buildSessionFactory(registry);
    } catch (HibernateException ex) {
      // Make sure you log the exception, as it might be swallowed
      System.err.println("Initial SessionFactory creation failed." + ex);
      throw new ExceptionInInitializerError(ex);
    }
  }
}

那么，现在查询

 SELECT COUNT(*) FROm pg_stat_activity;

返回6，其中一个是psql客户端。即使在重新请求页面一分钟之后。我认为，这是一个进步。

剩下的唯一一件事是让 Hibernate 可以与 Tomcat/lib 文件夹中的 postgresql-jdbc.jat 一起工作，而不使用 WEB-INF/lib 中的 jar。我读到将 postgresql-jdbc.jar 放入 WEB-INF/lib 可能会导致内存泄漏。

附言我还读到，Hibernate 应该在 session 提交或回滚时自动关闭连接，我不需要显式关闭连接。

感谢您的建议，因为我总是需要一个让我睁大眼睛的人。