LoginServlet tries to create a velocity.log file in the tomcat root and fails when there is no write access for it

Also see http://hippo.2275632.n2.nabble.com/NullPointerException-when-accessing-login-tt6808331.html

Hey, I've got more detailed stack trace:

java.lang.NullPointerException
at org.apache.velocity.runtime.RuntimeInstance.parse(RuntimeInstance.java:1103)
at org.apache.velocity.runtime.RuntimeInstance.parse(RuntimeInstance.java:1086)
at org.apache.velocity.runtime.RuntimeInstance.evaluate(RuntimeInstance.java:1199)
at org.apache.velocity.runtime.RuntimeInstance.evaluate(RuntimeInstance.java:1165)
at org.apache.velocity.app.Velocity.evaluate(Velocity.java:191)
at org.hippoecm.hst.security.servlet.LoginServlet.renderTemplatePage(LoginServlet.java:486)
at org.hippoecm.hst.security.servlet.LoginServlet.renderAutoLoginPage(LoginServlet.java:420)
at org.hippoecm.hst.security.servlet.LoginServlet.doLoginLogin(LoginServlet.java:269)
at org.hippoecm.hst.security.servlet.LoginServlet.doGet(LoginServlet.java:194)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302)
at org.apache.catalina.authenticator.FormAuthenticator.forwardToLoginPage(FormAuthenticator.java:321)
at org.apache.catalina.authenticator.FormAuthenticator.authenticate(FormAuthenticator.java:245)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:528)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:662)

The problem appeared to be in velocity. It's trying to create velocity.log file in the tomcat root and throws exception because of failure.

The quick and *dirty* workaround (which worked for me) was: sudo chmod a+w /var/lib/tomcat6
I'll update you with proper solution as soon I find it.