Hehe, your playing with fire there. ;-) As you are aware each request is processed in its own thread. The actual instance of the action that singleton is called from is unimportant, you could have several threads calling it simultaneously - all from the same actions code. What this means of course is that your singleton probably needs to be threadsafe. Depending on what its doing this often means making appropriate use of the "synchronized" keyword - either within the code of the singleton itself, or by synchronizing in your code everywhere you call it. Having done this, only one thread will get to play with the singleton at a time - the others blocking until they get a chance (beware of deadlocks!) - this could have a performance impact if its code thats used a lot. The next thing you need to be aware of is that your singleton is only a singleton within that JVM (or ClassLoader to be precise) - if you are running in a clustered environment each JVM will have its own version of your singleton. If you have not thought through the consequences of this, you will probably run into trouble.
I did a quick web search. Have a read of these - Ive not had time to look at them probably myself but they should help your understanding. http://www.javaworld.com/javaworld/jw-01-2001/jw-0112-singleton.html http://www.javageeks.com/Papers/JavaStatics/JavaStatics.pdf -----Original Message----- From: Mohan Radhakrishnan [mailto:[EMAIL PROTECTED]] Sent: Saturday, November 16, 2002 18:26 To: 'Struts Users Mailing List' Subject: action calling Singleton Hi, What effect does a Singleton class have when it is called by the Action? I read that the Action is reused. It is just a simple file save utility but multiple users might be calling it from their actions at the same time. Is it recommended to use a utitily like this ? The upload utility is an example. If multiple users upload, and every file is saved in the same directory, the java directory handle might have to be shared. Is that right ? Won't it result in locking of the directory ? Thanks, Mohan -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
