严重: Servlet.service() for servlet [dispatcherServlet] in context with path [/demo] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause

java.lang.NullPointerException

	at com.thon.controller.system.WelcomeController.listUser(WelcomeController.java:61)

	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:601)

	at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)

	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)

	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)

	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:746)

	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:687)

	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)

	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)

	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)

	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915)

	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:811)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)

	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)

	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

	at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:233)