When Jetty is started with JSP 2.1, and then a context is stopped and started using JMX, the temp directory for the context is deleted but not created.
After restart, the following message is logged:
WARN EmbeddedServletOptions PWC5963: The scratchDir you specified: <temp_dir_name>\jsp is unusable.
If Jetty is started without JSP, the problem does not appear.
In org.mortbay.jetty.webapp.WebAppContext getTempDirectory(), change the initial test from
if (_tmpDir!=null && _tmpDir.isDirectory() && _tmpDir.canWrite())