ERROR [xxxxxx] ApplicationDispatcher[xxxxx] Servlet.service() for servlet jsp threw exception

[aba]

Lately i have been coming across an Error --> Application Dispatcher[]
in dimension 2.4, This comes for various reasons, all of which
haven't been discovered yet. I will list the ones which have been
found. if any one else come up with anything else please put it in
this thread...

1. First time when we faced this issue was due to JAVA version. the
latest version of java [JDK 1.7] was used then the inboxes would come
fine but without any data columns or column headings, only the inbox
name and the buttons if any will come up to display, and the editor
portlets will be showing, [modelname] is temporarily
available...... , in the error log you will be getting some thing
like this

-----------------------------------------------------------------------------------
2008-06-18 13:36:55,140 ERROR [org.jboss.web.localhost.Engine]
ApplicationDispatcher[/ [friendly url] /] Servlet.service() for
servlet jsp threw exception
java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor335.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:
43)
-----------------------------------------------------------------------------------


2. When naming a public field, if you give a name which starts with a
number, for example 2ndhalfqry or something like that, the database
will accept it... ( checked with mssql 2005 ), when done via studio
it will also accept it without throwing any errors or warning popups.
When deployed and accessed via server, in editor screen the bar at the
top right corner will be running and in the error log you will be
getting an error like this..

-----------------------------------------------------------------------------------
14:12:35,421 ERROR [Engine] ApplicationDispatcher[] Servlet.service()
for servlet jsp threw exception
org.jdom.IllegalNameException: The name "2halfqryfrmchild" is not
legal for JDOM
/XML elements: XML names cannot begin with the character "2".
at org.jdom.Element.setName(Element.java:206)
at org.jdom.Element.<init>(Element.java:140)
-----------------------------------------------------------------------------------

3. The reason for this has been stated as theme issue, but still the
same theme is working with another database dump of the same
application........ you will get an error and you will not be able to
login in, and if you login then you will get the second of errors are
as below......

-----------------------------------------------------------------------------------
18:31:16,234 ERROR [Engine] ApplicationDispatcher[] Servlet.service()
for servlet jsp threw exception
java.lang.NullPointerException
at
org.apache.jsp.html.themes.HRMS.templates.portal_005fnormal_jsp._jspService(portal_005fnormal_jsp.java:
541)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
-----------------------------------------------------------------------------------

-----------------------------------------------------------------------------------
18:31:16,281 ERROR [Engine] ApplicationDispatcher[] Servlet.service()
for servlet jsp threw exception
javax.servlet.jsp.JspTagException
at com.liferay.common.taglib.IncludeTag.doEndTag(IncludeTag.java:71)
at
org.apache.jsp.html.common.themes.portal_jsp._jspx_meth_theme_include_0(portal_jsp.java:
411)
at
org.apache.jsp.html.common.themes.portal_jsp._jspService(portal_jsp.java:
360)
-----------------------------------------------------------------------------------

4. The reason for this is still unknown, the symptoms would be like
this, you will be able to login to application and you can browse
around, but no inbox would come up for display... once a reason is
found will post it here.. for this you will get an error something
like this...

-----------------------------------------------------------------------------------
2008-07-04 17:16:25,968 ERROR [org.jboss.web.localhost.Engine]
ApplicationDispatcher[/Subject/] Servlet.service() for servlet
sample_jsp_portlet threw exception
java.lang.NullPointerException
at org.jboss.mx.loading.LoadMgr3.beginLoadTask(LoadMgr3.java:153)
at
org.jboss.mx.loading.RepositoryClassLoader.loadClassImpl(RepositoryClassLoader.java:
464)
at
org.jboss.mx.loading.RepositoryClassLoader.loadClass(RepositoryClassLoader.java:
374)
-----------------------------------------------------------------------------------