Java Hibernate/C3P0 错误：“无法获取连接元数据。客户端检查连接的尝试已超时。”
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Java Hibernate/C3P0 error: "Could not obtain connection metadata. An attempt by a client to checkout a Connection has timed out."
提问by Allan
I'm trying to get some code I was passed up and running. It appears to use the Hibernate framework. I've gotten past most of the errors tweaking the configuration, but this one has me dead stumped.
我正在尝试获取一些我被传递并运行的代码。它似乎使用 Hibernate 框架。我已经克服了调整配置的大部分错误，但这个错误让我很难过。
It's trying to connect to two databases: gameapp and gamelog. Both exist. It seems to have issues connecting to gamelog, but none connecting to gameapp (later in the init, it connects to and loads other DBs just fine). Below, I've pasted the error and exception stack dump.
它试图连接到两个数据库：gameapp 和 gamelog。两者都存在。连接到游戏日志似乎有问题，但没有连接到游戏应用程序（稍后在初始化中，它连接到并加载其他数据库就好了）。下面，我粘贴了错误和异常堆栈转储。
I imaging there's something else in the configs, so I've also included the configuration file for that db. I know this is very vague, but I'm hoping some pro can see the stupid mistake I'm missing.
我想象配置中还有其他东西，所以我还包含了该数据库的配置文件。我知道这很模糊，但我希望一些专业人士可以看到我遗漏的愚蠢错误。
<?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>
Exception and stack trace:
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##代码##0(Unknown Source)
at com.server.databaseop.goodOp.GoodOpImpl.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$ScheduledFutureTask.access1(ScheduledThreadPoolExecutor.java:165)
at java.util.concurrent.ScheduledThreadPoolExecutor$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
采纳答案by Tyler Szabo
If you have set C3P0's "checkoutTimeout" property to something other than 0 you might be timing out too quickly (that was my problem, solution: bumped it to 2000 milliseconds from 500).
如果您已将 C3P0 的“checkoutTimeout”属性设置为 0 以外的值，您可能超时太快（这是我的问题，解决方案：将其从 500 增加到 2000 毫秒）。
Alternatively, there's a workaround for this warning:
或者，此警告有一个解决方法：
Set the hibernate.temp.use_jdbc_metadata_defaultsproperty to false.
将hibernate.temp.use_jdbc_metadata_defaults属性设置为false。
Found this in http://www.docjar.com/html/api/org/hibernate/cfg/SettingsFactory.java.html, though there may be side effects of not having Hibernate extract JDBC Metadata defaults.
在http://www.docjar.com/html/api/org/hibernate/cfg/SettingsFactory.java.html 中找到了这个，尽管没有 Hibernate 提取 JDBC 元数据默认值可能会有副作用。
回答by Pascal Thivent
Check if you can connect to the gamelog mysql database on the command line with the root user and no password (!). As a side note, I'd recommend to set a password for root and to use a different account to connect to the database from your application, but that's another story.
检查您是否可以在命令行上使用 root 用户且无需密码 (!) 连接到 gamelog mysql 数据库。作为旁注，我建议为 root 设置密码并使用不同的帐户从您的应用程序连接到数据库，但这是另一回事。
回答by MJB
Actually that's not even an authentication error. Is MySQL even running or bound to localhost?
实际上，这甚至不是身份验证错误。MySQL 是否正在运行或绑定到本地主机？
does telnet 127.0.0.1 3306 work? if so, install the mysql client on the box and try
telnet 127.0.0.1 3306 能用吗？如果是这样，请在盒子上安装 mysql 客户端并尝试
mysql --user=root --ip=127.0.0.1 and see what happens
mysql --user=root --ip=127.0.0.1 看看会发生什么
