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2 wars sharing code

I need to create 2 war applications deployed on tomcat server.
One of the applications have the exact same logic and code as the other application but with added changes to the view and controllers.
Then App1 and App2 will have the same code to access data and I don't want to duplicate code.
My idea is create 2 WARs and these WAR files should use a library or other project (I don't know) that has access to the database.
Which solution is the best for performance?

Option 1
If you are sharing code (and it's a big piece of code, which drives you crazy while uploading the war-files) it may be an option to create a jar containing the code and add the jar file to tomcats library-folder, which is ${CATALINA_BASE}/lib/
Note that this is usually not something you want to do lightly, because that jar file will be available to ALL war-files on the tomcat, creating possible namespace-problems.
Option 2
If sharing the code with all the projects on the application-server is not an option you'll have to add the jar-file to the projects and add it into it's classpath (which happens automatically within eclipse if you add the jar into ${PROJECT_ROOT}/WebContent/WEB-INF/lib).
Preformance-wise this doesn't really make a difference since tomcat will load the class-files, which are not very big. The instances might be, but the type of deployment doesn't really have an impact upon instances.

If you want to use the same classes for both projects just simple create one .jar file which will contain those classes. Then add that .jar into your web projects' classpath and use it in both.

You can extract the common part out, and make it as a jar. And then two wars use this jar as library.
If you used maven for building your wars, it would be easier to build a project hierarchy.
something like:
parent
|_common(jar)
|_war1
|_war2

Tomcat - won't load my META-INF\services\javax.servlet.ServletContainerInitializer file?

I have a web project that has a \META-INF\services\javax.servlet.ServletContainerInitializer file with its content pointing to the fully qualified name of a class that implements the ServletContainerInitializer interface. I basically followed the example given here: http://nullhaus.com/2011/03/using-servlets-3-0-servletcontainerinitializer/
I put debug lines in my class that implements the ServletContainerInitializer interface and it never makes it there. Not even the default constructor...
My application folder structure is as follows:
\MyApp
\META-INF\services\javax.servlet.ServletContainerInitializer
\WEB-INF\classes\
... [list of classes and packages go here]
Any ideas what I need to check for??
Note 1: My Tomcat publishes from an exploded external folder that contains my application
Note 2: I started my Tomcat from Eclipse - if that makes a difference!

Well, I think that you'll need to wrap your initializer class (and it's services-related META-INF directory) into a separate *.jar and put it in the WEB-INF/lib.
This is a JAR service, so I guess it could have something to do with problems with discovering services in a *.war file. Moreover, it doesn't even help if you put your META-INF directory inside WEB-INF/classes and set unpackWAR=false in your Tomcat's server.xml.
HTH.

The first thing to check is that you are actually using Servlet 3.0 and not an earlier version. For Tomcat, this means that you must be using Tomcat 7.0.22
Second, make sure that the \META-INF\services\javax.servlet.ServletContainerInitializer file actually exists in the exploded war file.
Third, when in doubt, configure and start Tomcat directly (not from Eclipse) - I've seen developers have endless problems with configuration of Tomcat using the Eclipse plugin.

For tomcat to load the META-INF directory , it has to be in classes folder . If you are using maven project , just put the META-INF directory inside src/main/resources directory .. on mvn package the same will be copied to classes directory .. No need of separerate jar .. if jar is prefered you can use
HandlesTypes annotation ..

I would like to quote some good explanation from Mark Thomas <markt#apache.org> given on the user mailing list of Tomcat:
Service files are loaded by class loaders from the META-INF/services
directory.
*.jar!/META-INF/services
and
*.war/WEB-INF/classes/META-INF/services
are visible to class loaders
*.war!/META-INF/services
is not.
The servlet expert group recently discussed WAR vs JAR in the context of
Java 9 and mutli-version JARs. The conclusion was (I'm paraphrasing)
that WARs are not a specialised form of JAR and while they share a
common format a feature that is available to a JAR is NOT automatically
available to a WAR unless the Servlet spec (of Java EE spec) explicitly
states otherwise.
Containers are free to add container specific extensions if they wish
but they come with the usual (lack of) interoperability warnings.
http://mail-archives.apache.org/mod_mbox/tomcat-users/201808.mbox/

/WEB-INF/classes vs /WEB-INF/lib

I'd like to package my Java EE6 web classes (beans, filters, servlets) into jar and place it into /WEB-INF/lib/ directory along with other utility jars and abandon /WEB-INF/classes/ directory totally.
Are there any substantial differences between the two in terms of classloading, acessing application context, etc?
Thanks.
PS: Whenever googling any of java specs I'm always redirected to Oracle documentation index which is dozen clicks away from original url. Anyone knows what's happening there?

I'd go for /WEB-INF/classes. It allows you to run your application in debug mode and hot-swap classes on change. If you package everything as a jar, you'd have to repackage and redeploy the app every time you change a class.

Well, shortly: Imagine you have class org.example.Test.class, if you put it into jar and in WEB-INF/lib/ directory, and copy the same class into WEB-INF/classes/ then classloader of that application will use last one (from WEB-INF/classes/).
Sometimes you can use it as advantage - I have a library, and it has a bug... I look for source of that class (where bug is; I miss the part of how I know that bug is in that class, that's another story), I add that class to the project with fixed code, and it is compiled into WEB-INF/classes/ while library still exist in WEB-INF/lib/. Fixed class will be used until library will be fixed.

In Tomcat Servlet container's definition: WEB-INF\classes is searched before WEB-INF\lib. You can choose to delegate your classloading to your custom classloader - even then the order above is maintained.
If you choose to go with a different provider e.g. JBOss, Glassfish, Jetty it might have a different order, but I am not sure about those.

Different lib directories of JBoss

There is a number of different lib directories JBoss (5.1.0) uses: I can find jboss/lib, jboss/lib/endorsed, jboss/common/lib, jboss/server/default/lib and of course the jboss/server/default/deploy/myapp/WEB-INF/lib (am I missing something ?).
From the above, I know that I need to use the last one (WEB-INF/lib) to put any jars my app needs. What about all the others ? What is their use and what should I put there ? Why put it there and not in the WEB-INF/lib ?
Thanks !

Other folders are for different sorts of shared libs. For example, if you have 10 apps using same DB driver, there is really no reason to keep one db driver jar per application (i.e. 10 jars). In that case you can simply put it into jboss/server/<server config>/lib.
jboss/server/<server config>/lib: all libs here are shared between all apps in given server config
jboss/common/lib: shared between all server configs
jboss/lib: these are libs for server itself (if I am not mistaking, they are also on your app classpath)
jboss/lib/endorsed: this is the same as above, only if you put a lib here, it will always be found before similar lib in jboss/lib. The idea is similar to Endorsed Standards Override Mechanism of JDK

Java distribuion as jar file containg config, libs and deps

I am developing a framework that needs a lot of stuff to get working. I have several folders inside of my Eclipse project that are needed
[root]
- config
- src
- lib
- serialized
Also there are important files like the log4j.properties and the META-INF dir inside the src directory.
I wonder if there is a way to distribute one JAR containing all essential files so my gui will just have to import one jar. I guess that I have to exclude the config folder in order to make the framework configurable.
I also wonder, if there is a way to move for example the log4j.properties to the config dir so that I have one config folder containg all needed configurations?
Thanks for help and advise on this matter!
Marco

Yes, but not really. You can take all your dependencies, unpack them and simply merge them into a bigger jar. This is what the maven jar plugin does if you make a jar with dependencies. The only problem is that this might result in conflicting files (suppose two of your dependencies contain a log4j.properties). This is one of the problems when doing the above with some of the spring libraries for instance.
I think someone actually wrote a classloader that allows you to bundle the whole jar inside of your jar and use it as is. I'm not sure how mature that is though and can't at the moment recall the name.
I think you're better off distributing all your dependencies separately. Setting up the classpath is a bit of a pain but surely java programmers are used to it by now. You can add dependencies to the Class-Path header in your manifest file, in simple cases. Bigger libraries have to rely on the classpath being set up for them though.
As to the second part of your question, probably dropping the conf/ directory under META-INF is enough for its contents to be picked up. I'm not sure about this. I'm fairly sure it will always be picked up if you put its contents at the top level of the jar. In any case, this is a distribution problem. You can easily have a conf/ directory inside your source tree and have your build scripts (whatever you might be using) copy the files in it to wherever is most convenient.
As to your users configuring. Try to establish some conventions so they have to configure as little as possible. For things that must be configured, it's best to have a basic default configuration and then allow the user to override and add options through his/her own configuration file.

In terms of the resources, it is possible except that if you do that you are not going to be able to load resources (non class files) from the filesystem (via a file path).
It's likely that you're currently loading these resources from the file system. Once in the jar you need to load them as class path resources via the class.getResourceAsStream or similar.
As for the dependent jars you may have, it's common practice for these to be placed as extra jars on the classpath. I know it's complicates things but developers are used to doing this. The nature of the java landscape is that this is inevitable. What the spring framework for example does is supply a bundled zip file with the core jar and the jar dependencies included.
Is your library going to be used in an EE context or an SE context? If it is an EE context then you really don't have to worry about configuration and class path issues as the container takes care of that. In an SE context it is a lot more tricky as that work has to be done manually.