Managing system scoped jars with maven and the addjars plugin

When using some third party dependencies in a maven project you realize that sometimes some of jars are not available in any of the public maven repositories available (e.g. the oracle jdbc driver that is not available for copyright reasons)

When developing a team project and that you are required to use a jar of this type you have mainly 3 options :

1. Using Maven repository repository manager

There are a few maven repository managers out there which allow mainly to mirror distant maven repositories such as maven central, by storing the remote jars locally and making them available inside the company

This is where you can store your companies jars and wars and some other jar not available in the public repositories

I will not go into the details of the different repository managers but there are mainly 3

• Sonatype nexus repository
• JFrog Artifactory
• Archiva

I never used Archiva but I really like Nexus. There is a nice comparison matrix over here so you can make and educated choice

Anyhow if you or your company have a repository manager you can easily install the required JAR on your repository.

Once the JAR is installed in the repository it will be available to anyone that uses the repository as long as your settings.xml file or pom.xml file are properly configured.

The main advantage if this approach is that once the JAR downloaded and installed in the repository manager it will be available for all the users and future projects

The main inconvenient is the fact that you need to install a repository manager

2. Installing the JAR in the maven local repository

Installing a JAR in the user's maven local repo is quite straightforward

a) Download the JAR to the local machine

b) Install the JAR in the local repository

    mvn install:install-file -Dfile=/data/downloads/ojdbc6.jar -DgroupId=com.oracle -DartifactId=ojdbc6 -Dversion=11.2.0.3

c) Declare the JAR as a maven dependency

   

       .....

      
          
              =com.oracle
              ojdbc6
              11.2.0.3
         
     

  

This is the quickest and simplest approach to implement

The major inconvenient is that every new developer will need to install the JAR in their local repository

3. Using the addjars shade plugin and system as dependency scope

Maven allows you to easily defined dependencies with a system scope. But there is a problem with system scoped jars. When packaging the application (WAR, JAR, etc.) the system scoped jars will not be included in the packaged result. Here is where the addjar plugins comes in handy, this plugin allows you to include system scoped jars when packaging the application

Below is a quick example of a simple java web app with system scoped jar (ojdbc6.jar) :

my-app
|-- pom.xml
`-- src
    |-- main
    |   `-- java
    |   `-- webapp
    |-- external
    |   `-- ojdbc6.jar   

As stated before if I run a mvn package on this project I will get a WAR file but the ojdbc6.jar JAR will not be included under WEB-INF/lib

Thankfully the addjars plugins comes to the rescue here this plugin will include your third party jar in your project's classpath when packaging

You can see below a sample configuration for the plugin in the pom.xml file :

   
...

  
      
       com.googlecode.addjars-maven-plugin
       addjars-maven-plugin
       1.0.5
          
             
                
                  add-jars
                
                
                  
                    
                      ${basedir}/external/
                    
                 
              
           
        
      
    
  
...

The main advantage is that once the pom.xml configured with the dependency and the plugin and the JAR committed into the source control the building becomes transparent for the users

The main inconvenient comes from the fact that you will need to commit the JAR file in your source control repository and handle JAR versions manually

It's good to note that the add-jars plugin requires maven 3.0.3+