Connections could not be acquired from the underlying database!解决办法

今天程序遇到了下述问题
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 ds.util.C3P0Demo.getConn(C3P0Demo.java:27)
 at ds.biz.channel.channelBean.getAll(channelBean.java:38)
 at ds.web.channel.ChannelAction.getAll(ChannelAction.java:66)
 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.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:270)
 at org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:187)
 at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
 at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
 at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
 at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
 at java.lang.Thread.run(Thread.java:595)
出现这种问题有以下几种情况:
1，驱动配置有误：driver=com.mysql.jdbc.Driver
2，数据库连接地址有误：url=jdbc:mysql://localhost:3306/test?3useUnicode=true&characterEncoding=utf8
3，密码或帐号有误：username=root
      password=root
4，数据库未启动或无权访问
5，项目未引入对应的驱动jar包mysql-connector-java-5.1.6-bin.jar
6,mysql root没有远程访问的权限，需要增加权限，增加权限的步骤如下：
进入mysql数据库：
grant all privileges on *.* to 'root'@'%' identified by 'root' with grant option;
flush privileges;


最主要的时检查一下数据库的名字和数据库的连接信息的数据库的名字是否一致，一般都是这个错误！