Servlet.service() for servlet spring threw exception
java.lang.NullPointerException
     at org.controller.SimpleController.onSubmit(SimpleController.java:38)
     at org.springframework.web.servlet.mvc.SimpleFormController.onSubmit(SimpleFormController.java:387)
     at org.springframework.web.servlet.mvc.SimpleFormController.processFormSubmission(SimpleFormController.java:272)
     at org.springframework.web.servlet.mvc.AbstractFormController.handleRequestInternal(AbstractFormController.java:268)
     at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
     at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771)
     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)
     at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:563)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
     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:230)
     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:104)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
     at java.lang.Thread.run(Thread.java:619)
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:659)
     org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:563)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:803)