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Maven - Handling Snapshot Dependencies

I have the following maven dependency in my web application POM, which in turn should pull other dependencies:
<dependency>
<groupId>com.my.libraries</groupId>
<artifactId>my-libs</artifactId>
<type>pom</type>
<version>1.6-SNAPSHOT</version>
</dependency>
NOTE I had release 1.5 for my-libs artifact previously pulled during an older build. But I have later upgraded the version to 1.6-SNAPSHOT. mathlibrary artifact wasn't present in 1.5 release.
I am expecting some jars to be present as part of my-libs artifact verson 1.6-SNAPSHOT which wasn't present in 1.5 - the pOM is below:
<!-- all the usual POM descriptionsm for my-libs -->
<groupId>com.my.libraries</groupId>
<artifactId>my-libs</artifactId>
<version>1.6-SNAPSHOT</version>
<packaging>pom</packaging>
<!-- continues... all normal stuff, nothing to see here :'/ -->
<dependency>
<groupId>com.my</groupId>
<artifactId>mathlibrary</artifactId>
<version>1.0</version>
</dependency>
<!-- continues -->
I expected that mathlibrary jar would be pulled if I do mvn package for my project. But when I looked at the lib folder for my webapplication the jar wasn't there. I then checked my .m2 directory contents and it seems that only version 1.5 is present, so 1.6-snapshot wasn't automatically installed. From here, I am thinking that if a release version is pulled before, it doesn't pull the next SNAPSHOT?
After I manually installed my-libs artifact using mvn clean install - on the next build for my web application it pulled the jars correctly. Does this mean that my package phase is defined not to automatically pull the SNAPSHOT dependencies? or is this something expected (i.e. I have to manually run install phase it if it's not a release version) ?

Use mvn package pulls all SNAPSHOT dependencies from your local repository (and also updates your local repository from a remote repository every 24 hours, if the artifact comes a remote one).
I do not really understand what you mean by "manually installed my-libs" because there is no automatic way to install artifacts (except for CI servers, that install/deploy on checkin). If you want to use an artifact (like my-libs), you need to build it and put it in the local repository -- and you do this by using mvn install.

Answer to your question depends on which packaging you are using in your pom.xml and on which plugins have executions tailored to the packge phase. When dependencies are processed, Maven usually resolves them, which means that corresponding jar files will be in your local repository.
Getting jar files in your target folder (as is, or unpacked) is a result of some plugin's work (such plugin would execute a mojo at prepare-package or package phase (usually). So, make sure you use proper packaging (such as war) or e.g. "assembly" plugin (which can repack dependencies for you).
To make your dependency artefacts available for resolution and further use, you should either deploy them to a remote repository, or install them to local repository.

After reading #JFMeier answer on this, I did the following:
1) Removed all release/snapshots from my .m2 directory.
2) Changed my web app POM to use 1.5 release for my-libs
3) Kicked off the build.
4) Once the build finishes, I confirm that mylibraries jar hasn't been deployed in my final web application directory in tomcat's WEB-INF\lib
5) Repeated steps 2-4 - BUT changed the version to 1.6-SNAPSHOT for my-libs.
6) Now I can see the expected result.

Maven is only getting into repository (either global or local) when you make a mvn install. With Maven Install, Maven checks if all the POM libraries are present in your project and downloads from repositories into your project if some are missing. If you do a Maven package, it only packages the libraries present in your project.

Install library jar in pom maven

I have Java Maven Project with a folder lib with all jars that must be included in my project.
I don't know how I have to modify the POM to add all libraries. I want that Maven uses this libraries and I can use all in the project.

Lets be frank here: you are basically asking how to use Maven but then not use it at the same time. Maven is built around the fact that dependencies are managed from dependable repositories and then you come along and want to bypass that entire system by having local jars anyway as you would have in a project not managed through Maven - like one that is built with ANT.
The true clean solution to "not getting jars from a Maven repository" is to still get them from a repository - your own. Setup a local repository and put your third party dependencies there, then configure your Maven build to know about that local repository. If they are actually dependencies that exist in Maven central then you can setup your local repository to proxy them rather than manually installing them yourself.
http://maven.apache.org/repository-management.html
If you are using the release management features of Maven (or something like Hudson) then you should actually already have such a thing to stick your generated release artifacts into.

You have to know which libraries are you using. Imagine that you use in your project the joda-time library.
So you have to search your libraries (in this case joda-time) in maven repositories and add to your pom.xml like the following:
<dependency>
<groupId>joda-time</groupId>
<artifactId>joda-time</artifactId>
<version>2.7</version>
</dependency>
Here the Maven repository --> Maven Repo

add external jar to our dependency

There is a jar file lets say "abc.jar" which maven dependency does not exist(ie created a jar by using java command of own classes). I want to add this jar as maven dependency so that at build time it will automatically copy that jar in lib folder as like other maven dependency. how i will do. please help .

Add it as a dependency with a system scope. See the docs here.
However, rather than adding it as a system dependency it might be better to mavenize the jar itself, then you can build and install it into your dependency management system.
Also, see this question: Can I add jars to maven 2 build classpath without installing them?

You can use the systemPath attribute in the dependency tag in the POM file of your project.
In your pom.xml, use the following snippet corresponding to abc.jar:
<dependencies>
<!-- Other dependencies -->
<dependency>
<groupId>abc</groupId>
<artifactId>x</artifactId>
<version>1.0</version>
<scope>system</scope>
<systemPath>{path_to_abc.jar}</systemPath>
</dependency>
</dependencies>
The scope parameter corresponding to this artifact must be set to system, for the artifact to be picked up from the specified systemPath.
Hope this helps!

A normal maven dependency is always resolved by looking into a repository. So you must put your JAR file into a repository.
You could install your JAR into your local repository. Have a look at the install plugin. The install-file goal is your friend.
If other developers also need this JAR (because they are working with the same project), they either need to install it locally too, or - better - you deploy the JAR to a remote repository. Have a look at the deploy plugin. Here the deploy-file goal is your friend. For deploying artifacts, you need a repository manager like Nexus or Artifactory.
However, a dependency could also have the system scope (look at the other answers).

Configure Maven To Create An Archive File With All Dependencies Defined in POM XML

I am working in a private network which doesn't have internet proxy.
I can not create a local repository as well which involves the bureaucracy, management won't allow it. I may be a long term fix but not the solution for the question I asked.
I can not keep maven as a build tool as it requires the direct or indirect internet connection.
I HAVE to use ANT for building the project hence using maven in offline mode also not an option for me.
But I still want to use the maven dependency management for collecting all the jars in a one archive smartly.
My plan is to generate a ZIP file containing dependencies resolved using maven. And then we will share this ZIP file to all developers working inside a private network which doesn't have internet connection.
To do so I will get a temporary access to a computer which is having internet connection and from there I will define a dummy POM with all the dependencies required.
Now the question is how do I generate a ZIP file ( not a single jar ) using maven which contains all the dependencies defined in POM.

while what youre suggesting is technically possible, it is (in my opinion) not the best solution to your problem.
your statement that
it requires the direct or indirect internet connection
is not accurate. what maven requires is a maven repository (or a set of them) to fetch stuff from. the best solution to your problem would be to install a local maven repository inside your organization's network. the 2 most popular choices for a loaclly-run maven repository seem to be nexus and artifactory - both offer free open source versions and paid supported pro versions.
once you set up a maven repository inside your organization's network and populate it with the artifacts you require you can simply configure all of your project's pom files to go to those repositories. for example, to configure maven to use your repo instead of maven central, you can do this:
<repositories>
<!-- override central -->
<repository>
<id>central</id>
<url>http://your.repo.location</url>
</repository>
</repositories>
you will need to map a plugin repository in a similar fashion.
its also possible to achieve this by configuring the maven settings.xml file in each user's home directory if you dont want this in the pom files but from my experience its less error-prone this way

use following command to build Maven project offline.
mvn -o package
Refer this and this for more information.

I ended up with a smart hack which lets me do dependency resolution and archiving!
I am creating a dummy maven web project with all the dependencies defined in pom xml.
Now the war packaging mode is used by default for web applications.
I simply install the maven project from internet facing machine.
I get all the dependencies and transitive dependencies in war file's "lib" directory with dependency naming version remaining unchanged !!!!
Copying and adding those files into an ANT project is a trivial task then..!

Maven: Add local dependencies to jar

I have a dependency
<dependency>
<groupId>de.matthiasmann</groupId>
<artifactId>twl</artifactId>
<version>1.0.0</version>
<scope>system</scope>
<systemPath>${project.basedir}/lib/TWL.jar</systemPath>
</dependency>
Then I execute mvn assembly:assembly. All natives files and remote maven libs are added, but there is no this jar.
UPDATE
When I am trying to run app by java -jar myjar.jar. It returns an error that there is no class from the above dependency (NoClassDefFoundError : de.matthiasmann.twl.ForExample).
I want to add classes from this jar to myjar.jar (the same what maven does with remote dependencies). How I can configure maven to do that?

See Maven 2 assembly with dependencies: jar under scope "system" not included for why system dependencies are not included and how you can work around it, specifically the mvn install:install-file code is what you want.

You cannot use systemPath, unless your Java EE server/container has that jar configured.
Remember that maven is development and compile time only. Once the war file is built, maven has no effect except for having placed all the desired jars into the WEB-INF/lib folder.
When you specify system scope, it means that it is your responsibility to ensure that the jar is present when the war is deployed. You already have a framework to do that and you do not wish to encumber your build dependency with that jar, but you have to make it available thro Maven only during development.
The other similar scope is "provided". e.g., JBoss or your corporate common deployment Tomcat framework already provides many of the jars like Spring and Hibernate that are loaded by the server startup and common to all apps in the server. Therefore, you would not want maven build to include those into the war file.
The right way, Maven gurus would tell you. is to have your own maven server and build whatever artefacts you need into that server. However, occasionally that is not possible.
Therefore, on such occasions, I create project level repository that is distributed with the project and checked into version control. I run the command mvn install to create a project level directory called, say, "project-repo".
http://maven.apache.org/plugins/maven-install-plugin/examples/specific-local-repo.html (Due to familiarity, most of the time, I build the repo by hand rather than run mvn install).
Then in the POM, I specify file://${project.basedir}/project-repo as one of the repositories. The caveat with this is that in Windows, the slashes other than the pair after "file://" has to be back-slashes when referring to Windows file system paths.
<repositories>
<repository>
<id>my-repo1</id>
<name>my custom repo</name>
<url>http://ho.ho.ho</url>
</repository>
<repository>
<id>project-repo</id>
<name>my project repo</name>
<url>file://${project.basedir}\project-repo</url>
</repository>
</repositories>

YOu can implement this in many ways refer the blog below
http://blog.valdaris.com/post/custom-jar/

If you have such an dependency the best solution is first to use a repository manager and simply put that dependency into the repository manager and afterwards use it as simple dependency.