에러 타입 : org.springframework.web.util.NestedServletException
		에러 메세지 : Request processing failed; nested exception is java.lang.Exception: a의 값이 없습니다. [null]
		스택 트레이스 : 
		org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.Exception: a의 값이 없습니다. [null]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:656)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	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:76)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at com.innoforce.ultari.common.filter.StatisticsFilter.doFilter(StatisticsFilter.java:94)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:200)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.Exception: a의 값이 없습니다. [null]
	at com.innoforce.ultari.common.vo.ParamVo.getStringValue(ParamVo.java:231)
	at com.innoforce.ultari.main.MainController.control(MainController.java:88)
	at sun.reflect.GeneratedMethodAccessor189.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.springframework.web.servlet.mvc.multiaction.MultiActionController.invokeNamedMethod(MultiActionController.java:471)
	at org.springframework.web.servlet.mvc.multiaction.MultiActionController.handleRequestInternal(MultiActionController.java:408)
	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:790)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
	... 29 more