I work with Maven and I want to do a build with packaging ear, I want to add a dependency with scope system (...). But I don't found the jar in my generater ear!!!
Yes, that's just what you get when (ab)using a system scoped dependency which is supposed to be always available by definition. I wrote many times about this, for example in this previous answer that I'm quoting below:
  I already wrote many, many,
  really many times about this
  here on SO and in 99% of the cases,
  system scoped dependencies should be
  avoided. And I'll repeat what the
  Dependency Scopes mini guide says
  one more time:
  
  
    
    - system: This dependency is required in some phase of your
    project's lifecycle, but is
    system-specific. Use of this scope
    is discouraged: This is considered an
    "advanced" kind of feature and should
    only be used when you truly understand
    all the ramifications of its use,
    which can be extremely hard if not
    actually impossible to quantify.
    This scope by definition renders your
    build non-portable. It may be
    necessary in certain edge cases. The
    system scope includes the- <systemPath>element which points to
    the physical location of this
    dependency on the local machine. It is
    thus used to refer to some artifact
    expected to be present on the given
    local machine an not in a repository;
    and whose path may vary
    machine-to-machine. The systemPath
    element can refer to environment
    variables in its path:- ${JAVA_HOME}for instance.
  
  So, instead of using the system
  scope, either:
  
  
  - Add your libraries to your local repository via install:install-file.
  This is a quick and dirty way to get
  things working, it might be an option
  if you're alone but it makes your
  build non portable.
- Install and run an "enterprise repository" like Nexus, Archiva, or
  Artifactory and add your libraries via
  deploy:deploy-file. This is the
  ideal scenario.
- Setup a file based repository as described in this previous answer
  and put your libraries in there. This
  is the best compromise if you
  don't have a corporate repository but
  need to work as a team and don't want
  to sacrifice portability.
Please, stop using the system scope.