-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Mukarram,
On 4/20/2011 1:41 AM, Mukarram Baig wrote: > We are using tomcat in a non-clustered environment. We put certain > domain objects in the session [...]. The domain > objects are not serializable. No problem: there is no requirement that session objects be serializable unless your webapp is marked <distributable /> in web.xml. I suspect that Tomcat might complain if you put an object into a distributable webapp's session that does not implement Serializable. > We have randomly seen NullPointerExceptions > thrown when accessing properties of these domain objects via the session. You need perform null-checking when accessing session objects. :) > I > had read about Tomcat deciding to serialize sessions when it thinks that the > available memory is getting tight on some forum ( > http://www.coderanch.com/t/86379/Tomcat/Problems-disabling-Session-Persistence-Manager) This has to do with Tomcat restarting a webapp, not due to low-memory conditions. > but couldn't see the same in the servlet spec or documentation on tomcat's > site. http://tomcat.apache.org/tomcat-6.0-doc/config/manager.html You have to read between the lines a bit, here: the default Manager implementation persists sessions across webapp restarts using a file that defaults to "SESSIONS.ser" and standard Java serialization. Any session objects that are not Serializable will cause the session to fail to write to that file, and may possible corrupt the file causing all sessions to be lost. > If yes, under what > (approximate) conditions does tomcat decide to serialize sessions to disk > and back? During a webapp restart, unless you have configured another Manager implementation. I suspect not, since you haven't mentioned anything like that. > Overall, is the recommended approach to always make objects in the > session serializable? I wouldn't worry about it unless you a) intend to do distributable in the future or b) want to persist sessions across webapp restarts > Also, wouldn't it be great if a better exception like > NotSerializableException be thrown rather than the user stumbling over null > values and NPE's being thrown? You are probably getting both: NSE on the way out and NPE after your webapp starts up again and tries to read an empty session. Check your log files, especially catalina.out. - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk2u8KYACgkQ9CaO5/Lv0PDv6gCeLvwu4JFykrcsBEDrnaPQ6jc/ nyEAniP9O3B01I6AIVa9Y/tgDjNw9duN =I+u6 -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
