IllegalArgumentException in Servlet

Question

I am trying to migrate an existing application to weblogic.
One of our Servlet uses the servlet API to get the header "If-Modified-Since".
It works well on Tomcat and OC4J, but weblogic throws:
java.lang.IllegalArgumentException: Bad date header: 'Wed, 15 Oct 2008 18:37:31 GMT'
     at weblogic.servlet.internal.ServletRequestImpl.getDateHeader(ServletRequestImpl.java:983)
     at javax.servlet.http.HttpServletRequestWrapper.getDateHeader(HttpServletRequestWrapper.java:83)
     at com.jivesoftware.base.action.util.ResourceLoaderServlet.isModified(ResourceLoaderServlet.java:661)
     at com.jivesoftware.base.action.util.ResourceLoaderServlet.doGet(ResourceLoaderServlet.java:171)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
     Truncated. see log file for complete stacktraceThank you

Answer 1

First lesson: Google for "IllegalArgumentException: Bad date header". As soon as you see an error message you haven't seen before, google the parts of the message that are not specific to your application. You'll very often come close to a solution to the problem just with this information alone.
It appears from reviewing those search results that WebLogic is strictly validating the value of the "If-Modified-Since" header. the [RFC 822 spec|http://www.faqs.org/rfcs/rfc822.html] is pretty clear that the year should be 2 digits, and not 4.
Past that, I don't know that value was submitted, whether on the client side or the server side (this point is also raised in some of the search results), so it's impossible to say what erroneously entered that value.