com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException:是什么异常？？

com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: No operations allowed after connection closed.
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:888)
at com.mysql.jdbc.Connection.checkClosed(Connection.java:1877)
at com.mysql.jdbc.Connection.prepareStatement(Connection.java:4349)
at com.mysql.jdbc.Connection.prepareStatement(Connection.java:4315)
at org.lxit.extstu.all.Selection.selectGender(Selection.java:109)
at org.lxit.extstu.all.SelectionServlet.selectOperater(SelectionServlet.java:27)
at org.lxit.extstu.all.SelectionServlet.doGet(SelectionServlet.java:13)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:627)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
at java.lang.Thread.run(Unknown Source)

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