adding error diagnostics as to where servlet API is loaded from.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@5706 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/WebAppMain.java

@@ -75,7 +75,7 @@ public class WebAppMain implements ServletContextListener {
             try {
                 ServletResponse.class.getMethod("setCharacterEncoding",String.class);
             } catch (NoSuchMethodException e) {
-                context.setAttribute(APP,new IncompatibleServletVersionDetected());
+                context.setAttribute(APP,new IncompatibleServletVersionDetected(ServletResponse.class));
                 return;
             }
 

core/src/main/java/hudson/util/IncompatibleServletVersionDetected.java

 package hudson.util;
 
+import hudson.remoting.Which;
+
+import java.io.File;
+import java.io.IOException;
+
 /**
  * Model object used to display the error top page if
  * we find out that the container doesn't support servlet 2.4.
@@ -10,4 +15,13 @@ package hudson.util;
  * @author Kohsuke Kawaguchi
  */
 public class IncompatibleServletVersionDetected {
+    private final Class servletClass;
+
+    public IncompatibleServletVersionDetected(Class servletClass) {
+        this.servletClass = servletClass;
+    }
+    
+    public File getWhereServletIsLoaded() throws IOException {
+        return Which.jarFile(servletClass);
+    }
 }

core/src/main/resources/hudson/util/IncompatibleServletVersionDetected/index.jelly

@@ -5,9 +5,9 @@
     <l:main-panel>
       <h1><img src="${imagesURL}/48x48/error.gif" alt="[!]"/><st:nbsp/>Error</h1>
       <p>
-        We detected that your servlet container does not support Servlet 2.4.
+        We detected that your servlet container does not support Servlet 2.4
+        (servlet API is loaded from ${it.whereServletIsLoaded})
       </p>
-
     </l:main-panel>
   </l:layout>
 </j:jelly>
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