STRUTS2 label Error: Caught an exception while getting the property values of NULL

Java.lang.NullPointerException

At Com.opensymphony.xwork2.ognl.OgnlUtil.getBeanInfo (ognlutil.java:398)
At Com.opensymphony.xwork2.ognl.OgnlUtil.getPropertyDescriptors (ognlutil.java:344)
At Com.opensymphony.xwork2.ognl.OgnlUtil.getBeanMap (ognlutil.java:375)
At Com.opensymphony.xwork2.ognl.OgnlReflectionProvider.getBeanMap (ognlreflectionprovider.java:97)
At Org.apache.struts2.components.Debug.start (debug.java:71)
At Org.apache.struts2.views.jsp.ComponentTagSupport.doStartTag (componenttagsupport.java:53)
At Org.apache.jsp.web_002dinf.jsp.member2restaurant.searchpartner_jsp._jspx_meth_s_005fdebug_005f0 ( searchpartner_jsp.java:272)
At Org.apache.jsp.web_002dinf.jsp.member2restaurant.searchpartner_jsp._jspservice (searchPartner_jsp.java:183)
At Org.apache.jasper.runtime.HttpJspBase.service (httpjspbase.java:70)
At Javax.servlet.http.HttpServlet.service (httpservlet.java:728)
At Org.apache.jasper.servlet.JspServletWrapper.service (jspservletwrapper.java:432)
At Org.apache.jasper.servlet.JspServlet.serviceJspFile (jspservlet.java:390)
At Org.apache.jasper.servlet.JspServlet.service (jspservlet.java:334)
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.catalina.core.ApplicationDispatcher.invoke (applicationdispatcher.java:749)
At Org.apache.catalina.core.ApplicationDispatcher.processRequest (applicationdispatcher.java:487)
At Org.apache.catalina.core.ApplicationDispatcher.doForward (applicationdispatcher.java:412)
At Org.apache.catalina.core.ApplicationDispatcher.forward (applicationdispatcher.java:339)
At Org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute (servletdispatcherresult.java:164)
At Org.apache.struts2.dispatcher.StrutsResultSupport.execute (strutsresultsupport.java:186)
At Com.opensymphony.xwork2.DefaultActionInvocation.executeResult (defaultactioninvocation.java:374)
At Com.opensymphony.xwork2.DefaultActionInvocation.invoke (defaultactioninvocation.java:278)
At Com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept (parametersinterceptor.java:236)
At Com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept (methodfilterinterceptor.java:98)
At Com.opensymphony.xwork2.DefaultActionInvocation.invoke (defaultactioninvocation.java:249)
At Com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept (Exceptionmappinginterceptor.java : 187)
At Com.opensymphony.xwork2.DefaultActionInvocation.invoke (defaultactioninvocation.java:249)
At Cn.com.eatlab.web.AuthInterceptor.intercept (authinterceptor.java:74)
...........
ERROR Exceptionmappinginterceptor:38-caught An exception while getting the property values of null-class:com.opensymph Ony.xwork2.ognl.OgnlUtil
File:OgnlUtil.java
Method:getbeaninfo
Line:398-com/opensymphony/xwork2/ognl/ognlutil.java:398:-1
Org.apache.jasper.JasperException:Caught an exception while getting the values of Null-class:com.opensymphony . xwork2.ognl.OgnlUtil
File:OgnlUtil.java
Method:getbeaninfo
Line:398-com/opensymphony/xwork2/ognl/ognlutil.java:398:-1
At Org.apache.jasper.servlet.JspServletWrapper.handleJspException (jspservletwrapper.java:549)
At Org.apache.jasper.servlet.JspServletWrapper.service (jspservletwrapper.java:470)
At Org.apache.jasper.servlet.JspServlet.serviceJspFile (jspservlet.java:390)
At Org.apache.jasper.servlet.JspServlet.service (jspservlet.java:334)
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)


Debug go in to the Debug.class file to find such a piece of code:

Public Boolean start (writer writer) {
        Boolean result = Super.start (writer);


        Valuestack stack = Getstack ();
        Iterator iter = Stack.getroot (). Iterator ();
        List stackvalues = new ArrayList (Stack.getroot (). Size ());
        while (Iter.hasnext ()) {
            Object o = Iter.next ();
            Map values;
            try {
                values = Reflectionprovider.getbeanmap (o);
            } catch (Exception e) {
                throw new Strutsexception ("< Span style= "color: #ff0000;" >caught an exception and getting the property values of</span> "+ O, e);
            }
            Stackvalues.add (New Debugmapentry (O.getclass (). GetName (), values));
        }

        Addparameter ("Stackvalues", stackvalues);

        return result;
  }

Image

An object in root was found to be null, which is the reason for the exception,

Then found that the JSP page has a <s:debug></s:debug> tag, remove the label is normal.

But there is a new problem, the debug tag is debug, but because the debug tag produced a bug ...

Figure out why you need to know why there is a null object in Valuestack.getroot ().

It's about figuring out what valuestack is putting on ... And then... Analysis ...

Continued:

Asked in the forum, no results, calm analysis, the other pages can be normal, but this one page can not, so that the problem of the place in action inside,
Then we find a piece of code: Actioncontext.getcontext (). Getvaluestack (). push (member);
That's the problem, as you can imagine where the null in root came from, and then add an if (member! = null) {}, and the problem is solved.
Specifically do not know who added, used to do, so add an if to judge, is estimated to be used on the page, just a bit does not conform to our code's consistent style.
This is the problem, but also debug to debug to ...