Not sure if this well also help, here is another version of the stack trace (the one above was from we directly called sendRedirect from a ServletFilter, this one here, we do not, but it appears to be called by Comet):
java.lang.NullPointerException
at org.apache.coyote.tomcat5.CoyoteResponse.toAbsolute(CoyoteResponse.java:1610)
at org.apache.coyote.tomcat5.CoyoteResponse.sendRedirect(CoyoteResponse.java:1359)
at org.apache.coyote.tomcat5.CoyoteAdapter.postParseRequest(CoyoteAdapter.java:536)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:253)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:647)
at com.sun.enterprise.web.connector.grizzly.comet.CometEngine.executeServlet(CometEngine.java:609)
at com.sun.enterprise.web.connector.grizzly.comet.CometEngine.handle(CometEngine.java:356)
at com.sun.enterprise.web.connector.grizzly.comet.CometAsyncFilter.doFilter(CometAsyncFilter.java:84)
at com.sun.enterprise.web.connector.grizzly.async.DefaultAsyncExecutor.invokeFilters(DefaultAsyncExecutor.java:175)
at com.sun.enterprise.web.connector.grizzly.async.DefaultAsyncExecutor.interrupt(DefaultAsyncExecutor.java:153)
at com.sun.enterprise.web.connector.grizzly.async.AsyncProcessorTask.doTask(AsyncProcessorTask.java:92)
at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:265)
at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)
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