关于Spring mvc中session值赋值和获取问题?报错

import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;

@Controller
@RequestMapping("/Test2")
@SessionAttributes("first")
public class Test2Controller {

 @RequestMapping("/firstMethod")
 public String firstMethod (ModelMap map){
  System.out.println("执行firstMethod");
  map.addAttribute("first", "ok");
  return "search";
 }
 
 @RequestMapping("/secondMethod")
 public String secondMethod(@ModelAttribute("first") String first){
  System.out.println("执行了secondMethod");
  System.out.println("+++++"+first);
  return "search1";
 }
}

上面是我写的小例子，先是执行http://localhost:8080/@mvc/Test2/firstMethod.do，可以执行成功，但在执行http://localhost:8080/@mvc/Test2/secondMethod.do时就报错了，

报错内容如下：

2013-3-5 15:50:13 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet mvc threw exception
org.springframework.web.HttpSessionRequiredException: Expected session attribute 'first'
 at org.springframework.web.method.annotation.ModelFactory.initModel(ModelFactory.java:103)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:614)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
 at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
 at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 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:235)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:291)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
 at java.lang.Thread.run(Thread.java:619)

哪位高手指点一下，我这个是错在哪了，还是配置文件没配什么