VelocityServlet: Error processing the template

org.hibernate.exception.GenericJDBCException: Cannot open connection
javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Cannot open connection
	at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:630)
	at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:41)
	at com.dg.persistence.JPAPersister.begin(JPAPersister.java:110)
	at com.dg.webtools.velocity.VelocityBase.handleRequest(VelocityBase.java:139)
	at org.apache.velocity.servlet.VelocityServlet.doRequest(VelocityServlet.java:365)
	at org.apache.velocity.servlet.VelocityServlet.doGet(VelocityServlet.java:318)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:489)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:583)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:212)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
	at com.dg.webtools.filters.RefererFilter.doFilter(RefererFilter.java:65)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:662)
	at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:428)
	at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:360)
	at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:297)
	at com.dg.webtools.filters.LocaleFilter.doFilter(LocaleFilter.java:49)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
	at com.dg.webtools.filters.PersistenceFilter.doFilter(PersistenceFilter.java:27)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
	at com.dg.webtools.filters.MaintenanceFilter.doFilter(MaintenanceFilter.java:42)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:682)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:682)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:617)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:932)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1694)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: org.hibernate.exception.GenericJDBCException: Cannot open connection
	at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:103)
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:91)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
	at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:426)
	at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
	at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:119)
	at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:57)
	at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1326)
	at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:38)
	... 45 more
Caused by: java.sql.SQLException: Cannot get a connection, pool error Timeout waiting for idle object
	at org.apache.tomcat.dbcp.dbcp2.PoolingDataSource.getConnection(PoolingDataSource.java:142)
	at org.apache.tomcat.dbcp.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:747)
	at org.hibernate.connection.DatasourceConnectionProvider.getConnection(DatasourceConnectionProvider.java:69)
	at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:423)
	... 50 more
Caused by: java.util.NoSuchElementException: Timeout waiting for idle object
	at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:443)
	at org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:353)
	at org.apache.tomcat.dbcp.dbcp2.PoolingDataSource.getConnection(PoolingDataSource.java:136)
	... 53 more