Java Hibernate / C3P0错误：“无法获取连接元数据客户端尝试检出Connection的尝试已超时”

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如果您将C3P0的“ checkoutTimeout”属性设置为非0的值，则可能是超时太快了（这是我的问题，解决方案：将其从500提高到2000毫秒）。

或者，有一种解决此警告的方法：

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中可以找到此内容，但是如果不使用Hibernate提取JDBCMetadata默认值可能会产生副作用。

解决方法

我正在尝试获取一些传递并运行的代码。它似乎使用了Hibernate框架。我已经克服了调整配置时的大多数错误，但这使我陷入了困境。

它正在尝试连接到两个数据库：gameapp和gamelog。两者都存在。似乎有问题连接到gamelog，但没有问题连接到gameapp（在init之后，它可以连接并加载其他数据库就很好了）。在下面，我粘贴了错误和异常堆栈转储。

我想像一下配置中还有其他内容，所以我还包括了该数据库的配置文件。我知道这很模糊，但是我希望一些专业人士可以看到我所缺少的愚蠢错误。

<?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 metadatajava.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