java mysql被占用_Java DBCP数据库连接池被占满报错的解决方案
手机登录超时，查看后台日志，错误如下：org.apache.commons.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object
at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:104)
at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
at com.ultrapower.pasm.util.DBConnect.getConnection(DBConnect.java:98)
at com.ultrapower.ca.dao.UserDAO.getUserByMobile(UserDAO.java:31)
at com.ultrapower.ca.controler.CAServlet.getAccountByMobile(CAServlet.java:413)
at com.ultrapower.ca.controler.CAServlet.getUser(CAServlet.java:403)
at com.ultrapower.ca.controler.CAServlet.handleToken(CAServlet.java:310)
at com.ultrapower.ca.controler.CAServlet.reponse4common(CAServlet.java:244)
at com.ultrapower.ca.controler.CAServlet.service(CAServlet.java:90)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.util.NoSuchElementException: Timeout waiting for idle object
at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:825)
at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:96)
... 29 more
查看代码之后发现，在查询数据库时，只建立了数据库的链接，没有关闭数据库链接，连接池一直被占用，程序运行一段时间之后，连接池被占满，所以就会出现这种情况。
解决方案：
用完一个数据库链接之后就关闭连接。
try{
//创建数据库连接，执行SQL
}catch(Exception e){
}finally{
//关闭数据库链接
}
启发：写代码时一定要注意代码规范，注意细节问题，细节决定成败。