Java Hibernate/C3P0错误:"无法获取连接元数据.客户端检出连接的尝试已超时."

Question

我正在尝试获取一些我已经通过并运行的代码.它似乎使用Hibernate框架.我已经完成了调整配置的大部分错误,但是这个让我感到难过.

它正在尝试连接两个数据库:gameapp和gamelog.两者都存在.它似乎有连接到游戏日志的问题,但没有连接到gameapp(后来在init中,它连接到并加载其他DB就好了).下面,我已经粘贴了错误和异常堆栈转储.

我在configs中对其他东西进行了成像,所以我还包含了该db的配置文件.我知道这很模糊,但我希望有些职业选手可以看到我错过的愚蠢错误.

<?xml version="1.0" encoding="GBK"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://127.0.0.1:3306/gamelog</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>
        <property   name="connection.useUnicode">true</property>     
            <property   name="connection.characterEncoding">UTF-8</property>   
        <property name="hibernate.jdbc.batch_size">100</property>
        <property name="jdbc.fetch_size">1</property>
        <property name="hbm2ddl.auto">none</property><!-- update -->
        <property name="connection.useUnicode">true</property>
        <property name="show_sql">true</property>
        <!-- c3p0-configuration -->
        <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> 
        <property name="hibernate.c3p0.min_size">5</property>
        <property name="hibernate.c3p0.max_size">10</property>
        <property name="hibernate.c3p0.timeout">30</property>
        <property name="hibernate.c3p0.idle_test_period">30</property>
        <property name="hibernate.c3p0.max_statements">0</property>
        <property name="hibernate.c3p0.acquire_increment">5</property>      
    </session-factory>
</hibernate-configuration>

异常和堆栈跟踪:

2010-04-30 17:50:00,411 WARN [org.hibernate.cfg.SettingsFactory] - Could not obtain connection metadata
java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527)
    at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
    at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:35)
    at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:76)
    at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1933)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1216)
    at com.database.hibernate.util.HibernateFactory.<init>(Unknown Source)
    at com.database.hibernate.util.HibernateUtil.<clinit>(Unknown Source)
    at com.server.databaseop.goodOp.GoodOpImpl.initBreedGoods(Unknown Source)
    at com.server.databaseop.goodOp.GoodOpImpl.access$000(Unknown Source)
    at com.server.databaseop.goodOp.GoodOpImpl$1.run(Unknown Source)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:165)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:636)
Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@ca470 -- timeout at awaitAvailable()
    at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317)
    at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
    ... 18 more

Answer 1

如果你已经将C3P0的"checkoutTimeout"属性设置为0以外的其他属性,那么你可能会超时(这是我的问题,解决方案:从500增加到2000毫秒).

或者,这个警告有一个解决方法:

将hibernate.temp.use_jdbc_metadata_defaults属性设置为false.

在http://www.docjar.com/html/api/org/hibernate/cfg/SettingsFactory.java.html中找到了这一点,尽管可能存在没有Hibernate提取JDBC元数据默认值的副作用.