java.lang.NullPointerException at org.apache.myfaces.taglib.core.ViewTag.doStartTag

StackOverflow https://stackoverflow.com/questions/18129463

Pregunta

I am using MyFaces 1.2 with WAS 7.0 and Myeclipse Blue 10.7. I am getting the following error. I have researched Internet pretty thoroughly but to no avail. Logs don't present much. MyEclipse does not have JSF trace debug utility like IBM RAD.

[8/8/13 10:41:19:447 EDT] 00000018 webapp        E com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Servlet Error]-[/sui_index.jsp]: java.lang.NullPointerException
    at org.apache.myfaces.taglib.core.ViewTag.doStartTag(ViewTag.java:75)
    at com.ibm._jsp._sui_5F_welcome._jspx_meth_f_view_0(_sui_5F_welcome.java:755)
    at com.ibm._jsp._sui_5F_welcome._jspService(_sui_5F_welcome.java:121)
    at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:99)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
    at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1664)
    at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:940)
    at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:503)
¿Fue útil?

Solución

This exception is typical when you open a JSP page containing JSF components by a request URL which does not match the URL pattern of the FacesServlet. Basically, the JSF components in the JSP page are expecting to the FacesContext to be available by FacesContext#getCurrentInstance(). However, it returned null which in turn ultimately caused this NullPointerException.

Note that the stack trace also doesn't give any hint that the FacesServlet is properly been called. The call went directly to the container's own JSP servlet, which is HttpJspBase in case of Websphere, instead of JSF's own FacesServlet.

In order to sovle this problem, just look in the web.xml on which URL pattern the FacesServlet is been mapped. In JSF 1.x, this is usually *.jsf or maybe *.faces or very maybe /faces/*. Once you figured that, just make sure that the request URL, as you see in browser's address bar, matches exactly that URL pattern. So, instead of for example

http://example.com/context/sui_index.jsp

you should depending on the actual mapping be using either

http://example.com/context/sui_index.jsf

or

http://example.com/context/sui_index.faces

or

http://example.com/context/faces/sui_index.jsp

Either way, this way the FacesServlet will be invoked and be able to properly prepare the FacesContext as expected by the JSF components in the JSP page.

See also:

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