java.sql.SQLException: No operations allowed after statement closed.
	at com.mysql.jdbc.Statement.checkClosed(Statement.java:270)
	at com.mysql.jdbc.Statement.executeQuery(Statement.java:735)
	at database.MysqlConn.executeQuery(MysqlConn.java:44)
	at web.product.ProductDetail.doPost(ProductDetail.java:256)
	at web.product.ProductDetail.doGet(ProductDetail.java:58)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:114)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:91)
	at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:103)
	at filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:117)
	at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:73)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:175)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:240)
	at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:263)
	at com.caucho.server.port.TcpConnection.run(TcpConnection.java:481)
	at com.caucho.util.ThreadPool$Item.runTasks(ThreadPool.java:685)
	at com.caucho.util.ThreadPool$Item.run(ThreadPool.java:607)
	at java.lang.Thread.run(Thread.java:662)