Develop Reference

Maven multimodule library build

I'm developing library with Maven system, which is published in the Nexus repository.
In the nexus (and the maven build as well), the project produces the final jar named <projectName>-<version>.jar - this is exactly what I want.
Now, I decided to split the library into maven modules and therefore top level pom.xml have <packaging>pom</packaging>. The build also do not produce final <projectName>-<version>.jar, instead it produces <moduleName>-<version>.jar for each module.
What I want to achieve is to have the project split into modules and be able to produce final <projectName>-<version>.jar containing defined modules. Is this possible?
Is it possible to solve this issue migrating to the Gradle?

When you decided to split the library into multi modules it means that you decided to build them independently. So it's expected that each module creates it's own <moduleName>-<version>.jar.
Now when you use the created modules as dependencies for the bigger module with scope of compile maven would automatically add them to lib of the project.
So in your case you don't need to change packaging to pom and just add the modules as dependency in the pom.xml file and let maven to create the final jar for you.
Also if you want use pom packaging there is a good question here which might help you.

How to add and use one project in another project?

I have a project based on Spring which is running successfully. Now I have created another project based on Jersey which I want to integrate with spring project in Jersey.
I have gone through internet and I added spring project in the build-path of the Jersey project.
Here the problem is whenever I run my Jersey project, it has to execute the Spring project first.
How to configure spring project in Jersey?

You should consider using a dependency management/build tool such as Maven or Gradle.
This way each of your projects will be a module, which can be referenced from the other project as a dependency. You can still use the first project alone and the two-dependent projects alone as wall. Then the tool lets you just simply package the resulting project in a artifact such as WAR with all the dependencies.
Here is a quick maven tutorial - Maven in 5 Minutes
It is a good idea to use such a tool in any case as it has many additional advantages:
Lets you manage also your third party dependencies without needing to manually download the libraries and add them to the classpath
It is much easier to use such a project in cases like continuous integration.
You can run all your tests automatically during the build process to make sure everything works
It resolves transitive dependencies (dependencies of your dependencies)
It builds resulting archive file for you
You can have multiple profiles for different environments
...

Make both of your projects modules of one Maven parent pom project. This way you can build them both at the same time.

how to configure dependencies in maven pom.xml?

I am converting my simple working web application (runs from eclipse) to a maven project. This is my first maven project. I have 3 external jar dependencies to it and i added then to the pom.xml my build is failing saying that it can't find those 3 dependencies. here my pom.xml file
The build is saying that the 3 packages does not exist.
package javax.servlet does not exist
package org.apache.commons.codec.binary does not exist
package org.apache.commons.configuration does not exist
What i am missing? I am running my application from Mac and in the .m2/repository i see these 3 libraries/packages present.

You need to either remove the dependencyManagement tags that surround dependencies or add the dependencies again but nested within the project tag, i.e. at the same level as dependencyManagement.
dependencyManagement allows you to fix information about dependencies across a multi-module project - e.g. like version numbers - however you still need to provide a dependencies section alongside that so that Maven knows to include them.
If your project is not a multi-module project I would be tempted to not use a dependencyManagement section at all.

Just remove dependecyManagement tags

Dependencies in pom file - how does it work

I see some java programming examples on the internet which require me to use non-standard api's. So, the authors mentioned that a pom file is needed. I need to understand what is the purpose of this file and how does it get bound/"binded" to a java project.
When I add a non-standard jar to my project's build path in eclipse, is it the same as creating a pom file, doing something "magical" with it and then "binding" it to my project?
Or is it something else ?

The pom file is the main artifact of Maven, which is a build tool. Maven has many uses, but the most common is dependency management (build management is also a core feature). The way it works is that it allows you to define dependencies to external libraries that your project needs, and when you use Maven to build your project it will fetch these libraries from the web (external repositories) and add them to your built project. So it's an automatic handling of dependencies.
So if you for instance you want to include Spring in your Maven project, you edit your pom.xml and add
<dependency>
<groupId>org.springframework</group>
<artifactId>spring-core</artifactId>
<version>3.1.3.Final</version>
</dependency>
Where the groupId and artifactId is an unique identifier of the library you want to include, and version to select the right jar-file. Now, when the project is built with Maven (mvn install), it will try to fetch jar from the web and add it to the classpath of your built project.
Maven might be a bit hard to get started with, since there are so many options, but for learning Maven I would recommend starting with the build cycle and dependency management, and then move on to more advanced topics when you have a good understanding on how these things work.

JIBX MAVEN Problem

I am trying to use JIBX maven plugin in my Spring Web Service project,
My project has diferent layers (API-DAO-SERVICE vsvs..)
these layers are individual projects and has maven dependency each other.
In my WEB project's POM, I add other project as dependencies, and my mapping
classes are all in API project.
Even in my web project's POM includes dependencies of API project I could
not use that class'es in JIBX
BUT IF I put that class'es in WEB project's src/main/java directory there is
NO PROBLEM,
How can I use mapping classes that are other maven dependent projects.
Any help is really appreciated;
Thanks.

Generated sources are supposed to be compiled and packaged in the artifact at the end. The classes should thus be visible from your webapp.
Did you setup the maven-jixb-plugin as shown in Generate Java Sources from Schemas? If not, then maybe update your setup first and try again.
And if you are still facing problems, please show the relevant parts of your POM(s).