Connections could not be acquired from the underlying database
2008-09-04 10:59:34,515 [org.hibernate.cfg.SettingsFactory]-[WARN] Could not obtain connection metadata
java.sql.SQLException: Connections could not be acquired from the underlying database!
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:104)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:264)
at com.mchange.v2.c3p0.PoolBackedDataSource.getConnection(PoolBackedDataSource.java:94)
at com.mchange.v2.c3p0.ComboPooledDataSource.getConnection(ComboPooledDataSource.java:521)
at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)
at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:72)
at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1881)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1174)
at org.springframework.orm.hibernate3.LocalSessionFactoryBean.newSessionFactory(LocalSessionFactoryBean.java:825)
at org.springframework.orm.hibernate3.LocalSessionFactoryBean.afterPropertiesSet(LocalSessionFactoryBean.java:751)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1091)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:396)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:233)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:145)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:277)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:313)
at org.springframework.web.context.support.AbstractRefreshableWebApplicationContext.refresh(AbstractRefreshableWebApplicationContext.java:139)
at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:252)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:190)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3827)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4343)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:823)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:807)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:595)
at org.apache.catalina.core.StandardHostDeployer.install(StandardHostDeployer.java:277)
at org.apache.catalina.core.StandardHost.install(StandardHost.java:832)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:701)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:432)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:983)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:349)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1091)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:789)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1083)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:478)
at org.apache.catalina.core.StandardService.start(StandardService.java:480)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:2313)
at org.apache.catalina.startup.Catalina.start(Catalina.java:556)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:287)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:425)
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAcquire(BasicResourcePool.java:972)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:208)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:260)
... 43 more
2008-09-04 10:59:34,625 [com.mchange.v2.resourcepool.BasicResourcePool]-[WARN] com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1621fe6 -- 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).


[解决办法]
连接不上数据库，使用第三方软件(pl/sql或者sqlplus)在你这台机器上面，连接一下数据是否正常
[解决办法]
你使用的开发工具是什么?
[解决办法]
用户MyEclipse自带的数据库连接测试一下，驱动程序是否正常
如果连接不上则证明数据库的驱动程序有问题
1。仔细检查你的数据库名称及密码
2。再检查一下你的这个用户是否已经被锁定

[解决办法]
好像是没有读取到属性文件吧。。。
[解决办法]
和以前我遇到的情况是一模一样，运行一会以后就出现这个异常，这个好像是和数据库的服务有关，当时也不记得怎么解决的了！
[解决办法]
读取配置文件是否正常
[解决办法]
数据库里的mysql下的有个user表,
update user set Host ='%' where user ='root' ;
我的就是这样做的.
[解决办法]
<property name="driverClass">
<value>oracle.jdbc.driver.OracleDriver</value>
</property>
<property name="jdbcUrl">
<value>jdbc:oracle:thin:@192.168.1.80:1521:gdxltdb1</value>
</property>
<property name="properties">
<props>
<prop key="c3p0.minPoolSize">50</prop>
<prop key="hc3p0.maxPoolSize">200</prop>
<prop key="hc3p0.timeout">300</prop>
<prop key="c3p0.max_statement">10</prop>
<prop key="c3p0.testConnectionOnCheckout">true</prop>
<prop key="user">eais_xlt</prop>
<prop key="password">enstrong_xlt</prop>
<prop key="hibernate.connection.release_mode">auto</prop>
</props>
</property>