multiple context paths pointing to the same doc base?
Hi there, May be somebody can give me a quick answer with regards to T3.2.2. I need to have multiple context paths to point to the same doc base, say my server.xml has the following entries: Context path=/somectx docBase=d:/foo/bar debug=0 reloadable=false /Context Context path=/somectx1 docBase=d:/foo/bar debug=0 reloadable=false /Context Will the above config cause my webapp classes/servlets to be loaded twice through different classloaders, or TC is smart enough to realize it's the same webapp? Thanks, --V.
Re: multiple context paths pointing to the same doc base?
On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: Hi there, May be somebody can give me a quick answer with regards to T3.2.2. I need to have multiple context paths to point to the same doc base, say my server.xml has the following entries: Context path=/somectx docBase=d:/foo/bar debug=0 reloadable=false /Context Context path=/somectx1 docBase=d:/foo/bar debug=0 reloadable=false /Context Will the above config cause my webapp classes/servlets to be loaded twice through different classloaders, Yes. or TC is smart enough to realize it's the same webapp? It is *not* the same webapp. Every webapp must have a unique context path, and you have just defined two different context paths here. The fact that the document base is the same is just a coincidence. Thanks, --V. Craig
Re: multiple context paths pointing to the same doc base?
Thanks for the clarification, it makes sense. Is it according to the spec or just a peculiarity of Tomcat? Actually, I need just the opposite, is there any way to do this? Meaning different context paths - one webapp and one class loader... Thanks, --V. - Original Message - From: Craig R. McClanahan [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Wednesday, August 22, 2001 9:41 AM Subject: Re: multiple context paths pointing to the same doc base? On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: Hi there, May be somebody can give me a quick answer with regards to T3.2.2. I need to have multiple context paths to point to the same doc base, say my server.xml has the following entries: Context path=/somectx docBase=d:/foo/bar debug=0 reloadable=false /Context Context path=/somectx1 docBase=d:/foo/bar debug=0 reloadable=false /Context Will the above config cause my webapp classes/servlets to be loaded twice through different classloaders, Yes. or TC is smart enough to realize it's the same webapp? It is *not* the same webapp. Every webapp must have a unique context path, and you have just defined two different context paths here. The fact that the document base is the same is just a coincidence. Thanks, --V. Craig
Re: multiple context paths pointing to the same doc base?
On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: Thanks for the clarification, it makes sense. Is it according to the spec or just a peculiarity of Tomcat? Servlet 2.3 PFD2, Section 3.1 (emphasis added by **): A ServletContext is rooted at *a* known path within the web server. For example, a servlet context could be located at http://www.mycorp.com/catalog. All requests that begin with the /catalog request path, known as the context path, are routed to the web application associated with the servlet context. Actually, I need just the opposite, is there any way to do this? Meaning different context paths - one webapp and one class loader... Not that I know of. Of course, that begs the question of *why* you need this -- if everything is identical (as it would be if you got your wish), then what's the point? Thanks, --V. Craig - Original Message - From: Craig R. McClanahan [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Wednesday, August 22, 2001 9:41 AM Subject: Re: multiple context paths pointing to the same doc base? On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: Hi there, May be somebody can give me a quick answer with regards to T3.2.2. I need to have multiple context paths to point to the same doc base, say my server.xml has the following entries: Context path=/somectx docBase=d:/foo/bar debug=0 reloadable=false /Context Context path=/somectx1 docBase=d:/foo/bar debug=0 reloadable=false /Context Will the above config cause my webapp classes/servlets to be loaded twice through different classloaders, Yes. or TC is smart enough to realize it's the same webapp? It is *not* the same webapp. Every webapp must have a unique context path, and you have just defined two different context paths here. The fact that the document base is the same is just a coincidence. Thanks, --V. Craig
Re: multiple context paths pointing to the same doc base?
Thanks for the clarification, it makes sense. Is it according to the spec or just a peculiarity of Tomcat? Servlet 2.3 PFD2, Section 3.1 (emphasis added by **): A ServletContext is rooted at *a* known path within the web server. For example, a servlet context could be located at http://www.mycorp.com/catalog. All requests that begin with the /catalog request path, known as the context path, are routed to the web application associated with the servlet context. Well, I don't want to be picky but this quote doesn't emphasize that context is the same thing as web application, nor does it say that a web application cannot be shared by multiple contexts , it merely says that all requests are routed to the app associated with a particular context. In my understanding (which might be wrong btw) a webapp is something you package and distribute in a *.war file meaning classes, servlets, jsps, static html, and a webapp can be shared by different contexts. Isn't it more correct to have a class loader per *.war file (logically) than per contextpath? Or have it configurable since the spec is somewhat vague on this point? Actually, I need just the opposite, is there any way to do this? Meaning different context paths - one webapp and one class loader... Not that I know of. Of course, that begs the question of *why* you need this -- if everything is identical (as it would be if you got your wish), then what's the point? Without going into much details my particular application is relying on combination of context path and path info values to perform an internal lookup of some data. The data is cached and there's a cache maintanence thread running. So, I end up with as many caches and threads as many contexts I have configured. Of course I can try to interpret request URI's to extract the data I need, but using context path is much easier. Well, I guess I have no choice now :-| --V. Thanks, --V. Craig - Original Message - From: Craig R. McClanahan [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Wednesday, August 22, 2001 9:41 AM Subject: Re: multiple context paths pointing to the same doc base? On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: Hi there, May be somebody can give me a quick answer with regards to T3.2.2. I need to have multiple context paths to point to the same doc base, say my server.xml has the following entries: Context path=/somectx docBase=d:/foo/bar debug=0 reloadable=false /Context Context path=/somectx1 docBase=d:/foo/bar debug=0 reloadable=false /Context Will the above config cause my webapp classes/servlets to be loaded twice through different classloaders, Yes. or TC is smart enough to realize it's the same webapp? It is *not* the same webapp. Every webapp must have a unique context path, and you have just defined two different context paths here. The fact that the document base is the same is just a coincidence. Thanks, --V. Craig
Re: multiple context paths pointing to the same doc base?
On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: Date: Wed, 22 Aug 2001 11:19:47 -0700 From: Vladimir Grishchenko [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: Re: multiple context paths pointing to the same doc base? Thanks for the clarification, it makes sense. Is it according to the spec or just a peculiarity of Tomcat? Servlet 2.3 PFD2, Section 3.1 (emphasis added by **): A ServletContext is rooted at *a* known path within the web server. For example, a servlet context could be located at http://www.mycorp.com/catalog. All requests that begin with the /catalog request path, known as the context path, are routed to the web application associated with the servlet context. Well, I don't want to be picky but this quote doesn't emphasize that context is the same thing as web application, nor does it say that a web application cannot be shared by multiple contexts , it merely says that all requests are routed to the app associated with a particular context. Spec language is like legal contracts ... you've got to be familiar with the nuances :-). In particular the a above means one and only one. In my understanding (which might be wrong btw) a webapp is something you package and distribute in a *.war file meaning classes, servlets, jsps, static html, and a webapp can be shared by different contexts. From the perspective of the container, it is free (from a spec perspective) to do whatever it wants to with a WAR file. Some containers automatically expand them into unpacked directories (like Tomcat does by default), some run directly from a WAR (like Tomcat can), some store the static resources as BLOBs in a database. But the key point is this -- where the resources came from is irrelevant -- each web application is operated independently. Isn't it more correct to have a class loader per *.war file (logically) than per contextpath? Or have it configurable since the spec is somewhat vague on this point? You'll have to find me a servlet container vendor that interprets this the way you would like in order for me to think it is vague. Actually, I need just the opposite, is there any way to do this? Meaning different context paths - one webapp and one class loader... Not that I know of. Of course, that begs the question of *why* you need this -- if everything is identical (as it would be if you got your wish), then what's the point? Without going into much details my particular application is relying on combination of context path and path info values to perform an internal lookup of some data. The data is cached and there's a cache maintanence thread running. So, I end up with as many caches and threads as many contexts I have configured. Of course I can try to interpret request URI's to extract the data I need, but using context path is much easier. Well, I guess I have no choice now :-| One option you have is to put the classes that actually cache things into a common directory ($TOMCAT_HOME/lib or $CATALINA_HOME/lib). Such classes are shared across web apps, so this should accomplish your goal of having a single cache. They are loaded from a (common) parent class loader to the one for each web app. The only tricky part of this would be where the classes of the objects being cached are found. If your cache logic is in the parent class loader, but you try to instantiate an object of a class in the web app using the usual technique (Class.forName().newInstance()), you will get ClassNotFoundException errors. This can be worked around by noting that the Thread context class loader (guaranteed at least for Servlet 2.3 based containers) will always correspond to the webapp class loader, so your cache code can do something like this: String applicationClassName = ... class name of the object to create ... ClassLoader ccl = Thread.currentThread().getContextClassLoader(); Class clazz = ccl.loadClass(applicationClassName); Object instance = clazz.newInstance(); or something similar. --V. Craig
Re: multiple context paths pointing to the same doc base?
One option you have is to put the classes that actually cache things into a common directory ($TOMCAT_HOME/lib or $CATALINA_HOME/lib). Such classes are shared across web apps, so this should accomplish your goal of having a single cache. They are loaded from a (common) parent class loader to the one for each web app. I'm not using the latest servlet spec (2.3). Anyway, the simplest solutuion will be to put all my classes on the system classpath, this should work. I have no jsp's and don't need dynamic class reloading in production, so I beleive it's perfectly legal in my case. Thanks and regards, --V.
Re: multiple context paths pointing to the same doc base?
On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: One option you have is to put the classes that actually cache things into a common directory ($TOMCAT_HOME/lib or $CATALINA_HOME/lib). Such classes are shared across web apps, so this should accomplish your goal of having a single cache. They are loaded from a (common) parent class loader to the one for each web app. Wont this still result in one init() call per servlet per context? The only think you'll gain is the use of static variables right? Obviously these could be used to achieve the desired outcome, but you wouldn't get one context with two paths...? I'm not using the latest servlet spec (2.3). Anyway, the simplest solutuion will be to put all my classes on the system classpath, this should work. I have no jsp's and don't need dynamic class reloading in production, so I beleive it's perfectly legal in my case. you would be well advised to put it in a jar which you then place in tomcat's lib dir... that way its relatively easy to move your app. cheers dim
Re: multiple context paths pointing to the same doc base?
On Thu, 23 Aug 2001, Dmitri Colebatch wrote: Date: Thu, 23 Aug 2001 06:42:13 +1000 From: Dmitri Colebatch [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: Re: multiple context paths pointing to the same doc base? On Wed, 22 Aug 2001, Vladimir Grishchenko wrote: One option you have is to put the classes that actually cache things into a common directory ($TOMCAT_HOME/lib or $CATALINA_HOME/lib). Such classes are shared across web apps, so this should accomplish your goal of having a single cache. They are loaded from a (common) parent class loader to the one for each web app. Wont this still result in one init() call per servlet per context? Yes, but the second initialization can easily detect that the cache has already been initialized. The only think you'll gain is the use of static variables right? Obviously these could be used to achieve the desired outcome, but you wouldn't get one context with two paths...? Since the original objective was to share the cache, it seems to me that one versus two contexts is not a big deal, right? I'm not using the latest servlet spec (2.3). Anyway, the simplest solutuion will be to put all my classes on the system classpath, this should work. I have no jsp's and don't need dynamic class reloading in production, so I beleive it's perfectly legal in my case. you would be well advised to put it in a jar which you then place in tomcat's lib dir... that way its relatively easy to move your app. In fact, this is critical to the sharing solution. Eerything in Tomcat's lib directory is shared -- everything in /WEB-INF/classes or /WEB-INF/lib is not shared. cheers dim Craig
Re: multiple context paths pointing to the same doc base?
On Wed, 22 Aug 2001, Craig R. McClanahan wrote: Since the original objective was to share the cache, it seems to me that one versus two contexts is not a big deal, right? ahhh, sorry - missed the start of the thread... thought it was a more general one webapp thing... you would be well advised to put it in a jar which you then place in tomcat's lib dir... that way its relatively easy to move your app. In fact, this is critical to the sharing solution. Eerything in Tomcat's lib directory is shared -- everything in /WEB-INF/classes or /WEB-INF/lib is not shared. My reading of the suggestion was that the classes would reside elsewhere in the system but be in the startup classpath as startup - this would do the same thing but be a little more spread out... thats all my point was there (o: cheesr dim
