SSM exception analysis - java.lang.NullPointerException

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException

<pre>org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
	org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
</pre>
	<p><b>根本原因。</b></p>
	<pre>java.lang.NullPointerException
	com.iweb.service.impl.PersonServiceImpl.addPerson(PersonServiceImpl.java:19)
	com.iweb.controller.PersonController.addPerson(PersonController.java:23)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	java.lang.reflect.Method.invoke(Method.java:498)
	org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
	org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
	org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
	org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

Exception resolution:

solve!