JETTY-1362 Set root cause of UnavailableException

git-svn-id: svn+ssh://dev.eclipse.org/svnroot/rt/org.eclipse.jetty/jetty/trunk@3002 7e9141cc-0065-0410-87d8-b60c137991c4

VERSION.txt

@@ -1,5 +1,6 @@
 jetty-7.4.0-SNAPSHOT
  + 342504 Scanner Listener 
+ + JETTY-1362 Set root cause of UnavailableException
 
 jetty-7.4.0.RC0
  + 324110 Added test harnesses for merging of QueryStrings.

jetty-servlet/src/main/java/org/eclipse/jetty/servlet/ServletHolder.java

@@ -396,17 +396,21 @@ public class ServletHolder extends Holder<Servlet> implements UserIdentity.Scope
         }
     }
 
-
     /* ------------------------------------------------------------ */
 
-    private void makeUnavailable(Throwable e)
+    private void makeUnavailable(final Throwable e)
     {
         if (e instanceof UnavailableException)
             makeUnavailable((UnavailableException)e);
         else
         {
             _servletHandler.getServletContext().log("unavailable",e);
-            _unavailableEx=new UnavailableException(String.valueOf(e),-1);
+            _unavailableEx=new UnavailableException(String.valueOf(e),-1)
+            {
+                {
+                    initCause(e);
+                }
+            };
             _unavailable=-1;
         }
     }