Question

我遇到了hibernate无法打开连接的问题。我有一个DAO：

public class MyDao extends HibernateDaoSupport
{
    DataSource dataSource;

    public void setDataSource(DataSource dataSource)
    {
        this.dataSource = dataSource;
    }

    public MyPOJO findByQuery(int hour)
    {
        Query query = this.getSession().createSQLQuery(
        "SELECT * FROM MyPOJO WHERE someDate >= DATE_SUB(now(), INTERVAL ? HOUR)")
        .addEntity(MyPOJO.class);

        List<MyPOJO> results = query.setInteger(0, hours).list();

        return results;
    }
}

然后在测试用例中调用findByQuery（1）8次，它可以工作，但是如果我第9次调用它失败了：

org.hibernate.exception.GenericJDBCException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:103)
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:91)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:426)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:139)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1547)
at org.hibernate.loader.Loader.doQuery(Loader.java:673)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236)
at org.hibernate.loader.Loader.doList(Loader.java:2213)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2104)
at org.hibernate.loader.Loader.list(Loader.java:2099)
at org.hibernate.loader.custom.CustomLoader.list(CustomLoader.java:289)
at org.hibernate.impl.SessionImpl.listCustomQuery(SessionImpl.java:1695)
at org.hibernate.impl.AbstractSessionImpl.list(AbstractSessionImpl.java:142)
at org.hibernate.impl.SQLQueryImpl.list(SQLQueryImpl.java:152)
Caused by: org.apache.commons.dbcp.SQLNestedException: Could not retrieve connection info from pool
at org.apache.commons.dbcp.datasources.SharedPoolDataSource.getPooledConnectionAndInfo(SharedPoolDataSource.java:169)
at org.apache.commons.dbcp.datasources.InstanceKeyDataSource.getConnection(InstanceKeyDataSource.java:631)
at org.apache.commons.dbcp.datasources.InstanceKeyDataSource.getConnection(InstanceKeyDataSource.java:615)
at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:423)
... 35 more
Caused by: java.util.NoSuchElementException: Timeout waiting for idle object
at org.apache.commons.pool.impl.GenericKeyedObjectPool.borrowObject(GenericKeyedObjectPool.java:827)
at org.apache.commons.dbcp.datasources.SharedPoolDataSource.getPooledConnectionAndInfo(SharedPoolDataSource.java:165)
... 39 more

这就是我的hibernate属性：

<property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">
                org.hibernate.dialect.MySQL5Dialect
            </prop>
            <prop key="hibernate.current_session_context_class">
                thread
            </prop>
            <prop key="hibernate.format_sql">false</prop>
            <prop key="hibernate.show_sql">false</prop>
            <prop key="hibernate.use_sql_comments">false</prop>
            <prop key="hibernate.jdbc.use_get_generated_keys">true</prop>
            <prop key="hibernate.cache.use_second_level_cache">true</prop>
            <prop key="hibernate.cache.provider_class">
                org.hibernate.cache.EhCacheProvider
            </prop>
            <prop key="hibernate.connection.release_mode">auto</prop>
        </props>
    </property>

如果我将release_mode更改为'after_statement'（ala http://docs.jboss.org/hibernate/stable/core/reference/en/html_single/#transactions-connection-release）它会起作用，但我不明白这一点，并且觉得这只是一个更大的东西的创可贴，我做错了。

我也尝试刷新并关闭this.getSession（）也没有运气。我可以看到在对findByQuery（1）的所有调用完成后调用close（）。

这是在Hibernate 3.2.6，Spring 3.0和MySQL 5.1上。让我知道我可以提供更多信息。

Answer 1

Javadoc for HibernateDaoSupport.getSession()说：

请注意，这并不意味着从HibernateTemplate代码调用而只是在普通的Hibernate中代码。要么依赖线程绑定会话或与其结合使用 releaseSession（构造org.hibernate.Session）。

因此，通过getSession()获得的会话应通过releaseSession()发布：

public MyPOJO findByQuery(int hour) 
{ 
    Session s = null;
    try {
        s = this.getSession();
        Query query = s.createSQLQuery( 
        "SELECT * FROM MyPOJO WHERE someDate >= DATE_SUB(now(), INTERVAL ? HOUR)") 
        .addEntity(MyPOJO.class); 

        List<MyPOJO> results = query.setInteger(0, hours).list(); 

        return results; 
    } finally {
        if (s != null) this.releaseSession(s);
    }        
}

但处理会话的更好方法是使用HibernateCallback：

public MyPOJO findByQuery(int hour) 
{ 
    return this.getHibernateTemplate().executeFind(new HibernateCallback<List<MyPOJO>>() {
        List<MyPOJO> doInHibernate(org.hibernate.Session session) {
            Query query = session.createSQLQuery(    
                "SELECT * FROM MyPOJO WHERE someDate >= DATE_SUB(now(), INTERVAL ? HOUR)")    
                    .addEntity(MyPOJO.class);    
            return query.setInteger(0, hours).list();    
        }
    });
}

Answer 2

我通过更新mysql-connector-java-5.1.23-bin.jar文件解决了相同的问题。

Hibernate无法打开连接

2 个答案: