When the jars are packaged within EAR/lib, all works fine, but I cannot use this
approach and need to refer to them from the filesystem (maybe using absolute/relative paths)
Also adding the jars to the system classpath (using conf/jboss-service.xml) is not an option.
I have already defined a scoped classloading using loader-repository for the app in jboss-app.xml
Is there a way the scoped classloader for the app can access libraries from outside the EAR structure?
Technically, yes, at least with JBoss 4.2, and with luck it'll work in 5 as well.
This takes advantage of the fact that when JBoss's EARDeployer reads the path of each library in the application.xml file, it resolves the path relative to the base directory of the exploded EAR. If you put in relative paths with the appropriate number of ../ entries, then the path will resolve to anywhere on the filesystem you like, as long as it's navigable as a path relative to where the EAR is deployed (i.e. on windows, it has to be on the same drive).
Be aware, though, this is not standard behaviour, and isn't even guaranteed to work between different versions of JBoss.
Related
I'm doing some clean-ups in a GWT (no maven) project. It has a lot of jars added in WEB-INF/lib. I know the purpose of those jars (for example for REST service - luckily it's documented) so I wanted to put them in appropriate subfolders for nicer look.
After re-adding them to build path (as now they are in subfolders) I tried to run SuperDevMode and got multiple warnings:
Server class 'X' could not be found in the web app, but was found on the system classpath
and some errors like:
Cannot find a default implementation of the HK2 ServiceLocatorGenerator
When I put those jars back in WEB-INF/lib (without subfolders) and re-add to build path everything runs just fine.
My question is: can't/should't I use subfolders in WEB-INF/lib? If so, why?
Server class loader is programmed to look only into WEB-INF/lib, not other folder nor subfolders.
I strongly suggest to get into the maven world, it has a steep learning curve but it will assure to your project a solid foundation to grow on. Another big plus of Maven is that it can automatically pick up the latest security patch of your libraries (Equifax, anyone?).
Extract from the Apache Tomcat 7 Docs:
WebappX — A class loader is created for each web application that is deployed in a single Tomcat instance. All unpacked classes and resources in the /WEB-INF/classes directory of your web application, plus classes and resources in JAR files under the /WEB-INF/lib directory of your web application, are made visible to this web application, but not to other ones.
I have this third party framework which comes with a huge set of dependent libraries, which by the way, have not yet been indexed in any Maven repository. I want to use this framework with some Web Apps, but for obvious reasons I don't want to put all those libraries under WEB-INF/lib, neither do I want just to place them all under server/default/lib to avoid mixing them with other local and third party libraries.
Is there some way under JBoss 4.2.2 or higher to specify a custom lib directory for certain Web Apps? It's possible and/or advisable to have something like server/default/lib/myAppLib?
Any suggestion on this regard?
You can add the following entry in your server/default/conf/jboss-service.xml for putting your jars in server/default/myLibDir:
<classpath codebase="myLibDir" archives="*"/>
To my knowledge, you have three options:
Package you WARs in an EAR and move the library JARs out of WEB-INF/lib and
place them in a lib folder at the root of the EAR. No extra configuration required. This (non portable) solution is described in Configuring JBoss shared libs.
Move the library JARs out of WEB-INF/lib and place them into server/xxx/lib.
Deploy the JARs in the deploy/ folder and disable WAR file class loader isolation.
I don't recommend option #3. Option #2 is what you don't want. This leaves us with option #1 (which is IMO the cleanest).
Related questions
Jboss shared library
In JBoss can I configure a “shared library” location?
I have a jruby rails app that has some jar dependencies in rails lib/java. I prefer this to just putting them straight in lib as it separates my java libs from ruby libs. Works locally using jruby. Problem is, on deploy, tomcat is looking for a bunch of these jars (such as jruby) in WEB-INF/lib, not WEB-INF/lib/java.
I think i need to put some config in the web.xml that tells tomcat to also look in lib/java, but i can't find ANY docs on the matter.
I don't want to modify tomcat's system wide classpath, I just want to tell its class loader to check a directory other than WEB-INF/lib for this particular app only
Can anyone enlighten me on how to do this?
you can't change this directory, j2ee spec says that all libs go in WEB-INF/lib. That is where they are supposed to go.
Just stay with your two directories in your project folder, but join them, when creating your .war file. This should be pretty easy with apache ant and other build tools.
I have a few separate application projects (EARs) with multiple EJBs that I want to deploy to the same JBoss server. Now, some of the projects may have the same EJBs, but different versions. In similar circumstances, some projects may use different versions of the same "ordinary" classes (i.e. classes loaded within VM, without JNDI lookup).
With OC4J, this seems not to have been a problem, but now with JBoss, I get the impression that everything resides in the same "name space" (or class loader perhaps). Am I correct in this assumption?
Basically, what I want to do (or ensure) are two things:
From a client that does a JNDI-lookup of an EJB, I want to be able to indicate which application it resides in, so that the correct version of the EJB is returned.
From within an EJB, when instantiating a class, I want to ensure that the class is the one deployed with the same application (EAR) as the EJB was.
I think I read that you could configure some "isolation" properties for EJBs, am I guessing correctly in that might would solve my second point?
JBoss's default behaviour is to use a flat classloader. This reduces the footprint, but as you've found, it makes deploying multiple applications troublesome.
Thankfully, the fix is easy. In the ear-deployer.xml file in the deploy directory, make sure the following parameter is set:
<attribute name="Isolated">true</attribute>
This will give each deployed EAR its own classloader space. It will still be able to access stuff from the JBoss lib directory, but the deployed EARs will be invisible to each other.
You're correct that classes from different EAR's reside in the same "space". JBoss uses by default a flat classloader hierarchy, meaning that all classes (except for WAR packaged ones) are loaded by the same classloader. With the introduction of JBoss 5 there's a new standard profile that strictly follows the Java EE rules and thus supports isolated classloading. Older JBoss versions also support this behavior through the callByValue and isolate properties in the deployer configuraion.
If I have an dependency Jar for my application is it better to place it in the war files lib directory or to place it in the global application server (like Tomcat) lib directory? What do I gain by using one approach over another?
Diskspace springs to mind, but we live in a time when diskspace is cheap. Is there a memory usage difference? Can someone with more experience then me list the pros and cons of both options?
Generally speaking, it's much better to have WAR self-contained so you don't have to rely on the container configuration. It makes deployment much easier also. So try to put library in the WAR if you can.
However, I ran into cases when installing libraries to container makes sense. For example,
We have some internal libraries used by every webapp and they are huge. We install them to container so all the webapps use the same version and it saves on memory and diskspace too.
Libraries installed in WEB-INF/lib is not available to container. If you need to reference these in context.xml (like JDBC driver defined in Resources), you have to put them in server/lib.
If you want send log4j logs from all the webapps to the same file, you have to put log4j jar in the server/lib. Otherwise, each webapp uses its own logger.
If you want to use the container's resource management capabilities -- e.g. connecting to a SQL database and providing a JNDI lookup and connection pool for it -- then the container software itself will need access to the libraries and drivers to manage the resources.
Otherwise you probably don't want to install them in the server /lib directory and assume they are there and will work, as different web applications might have subtly different version requirements.
For a in-depth description of the class loader hierarchy implemented by Catalina, you should check Tomcat's Class Loaders HOW-TO. This will help you to understand when to make jars available to the container, to all webapps, to a single webapp only... and where to put them.