Example more generic usage multiproject goals.
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Key: MPMULTIPROJECT-55
URL: http://jira.codehaus.org/browse/MPMULTIPROJECT-55
Project: maven-multiproject-plugin
Type: Improvement
Versions: 1.4.1
Environment: Not of importance.
Reporter: Davy Toch
Assigned to: Brett Porter
One of the problems I have with Maven 1 (currently using maven-1.1-beta-1) is
knowing which goals can be executed on a certain project depends on the project
type. For example if the project is of type 'jar', then jar:install should be
called, while for a project of type 'ejb', ejb:install should be called. To
avoid that the developer needs to know this, it is possible to create a custom
maven.xml file. This could then include a goal 'install' that calls
'jar:install' for projects of type 'jar' and 'ejb:install' for projects of type
'ejb'. This way the developer could always call 'install', independent of the
current project type. This is also more consistent with the approach of most
IDE's (Eclipse, JBuilder, ...) where independent of project type, the tasks to
call are build, rebuild, clean, ....
However, the above approach would need a custom maven.xml file. In order to
avoid this, I had a look at the multiproject plugin that already has generic
goals (e.g. multiproject:artifact, multiproject:install, ...).
On the website of the multiproject plugin they propose e.g.
A. create a kind of 'master' project from which subprojects can inherit the POM
configuration
This master project has the following properties:
maven.multiproject.basedir=..
maven.multiproject.includes=*/project.xml
maven.multiproject.excludes=master/project.xml
Remark that with the above configuration the 'master' project has to be present
in a folder 'master' that is on the same level as its subprojects. This flat
project structure approach is chosen to avoid problems with the Eclipse IDE.
B. different subprojects are defined on the same level as the 'master' project
with the following property:
maven.multiproject.type=jar (or ejb, war, ear, ...)
This way you can e.g. call multiproject:artifact in the master project that
will automatically call the necessary goal in the subprojects (jar:jar,
ejb:ejb). However, if you only want to create the artifact for one subproject,
you should go to the subproject and call jar:jar, ejb:ejb, .... Therefore the
name of the goal to call is again different.
A solution for this I have thought of is : define each Maven project as a
multiproject, meaning that for the subprojects in B., the following properties
are also defined (but with different values then in A.):
maven.multiproject.basedir=${basedir}
maven.multiproject.includes=project.xml
maven.multiproject.excludes=
On the other hand it is also useful to define the following in the master
project:
maven.multiproject.type=master
With the above configuration you can:
- call multiproject:artifact in the 'master' project : will generate all
artifacts of the subprojects
- call multiproject:artifact in a subproject : will generate the artifact for
the subproject
- ...
Unfortunately, on
http://maven.apache.org/reference/plugins/multiproject/properties.html the
following is stated about the property maven.multiproject.includes:
"The 'top-level' project that you use to run maven multiproject must not be
included in the set of projects to be processed."
Question : why this restriction?
Remarks :
1. My multiproject approach has the following restrictions/problems:
- only subprojects of the 'master' project should create artifacts, not the
'master' project itself (the master project is only used to avoid POM
configuration duplication)
- the master project can't inherit from another project itself
- the subprojects are the base leaves in the inheritance tree, meaning that no
other projects can inherit from the subprojects
- reactor is always called
- not fully tested when calling the goals to create the website
- other problems?
2. Having maven.multiproject.type=master defined in the 'master' project is
e.g. useful when working in Eclipse, because calling the generic goal
multiproject:goal on the master project only calls the goal on the subprojects.
However, if you want to work with your projects in Eclipse, you should also be
able to generate the Eclipse project files (.classpath, ...) for the master
project because otherwise you won't be able to call Maven goals on the master
project from the Eclipse IDE. With maven.multiproject.type=master, you can have
a custom goal 'generate-eclipse-files' (or similar) in a script maven.xml:
<goal name="generate-eclipse-files">
<j:set var="type"
value="${context.getVariable('maven.multiproject.type')}"/>
<attainGoal name="eclipse"/>
<!--
If the current project type is 'master', then the eclipse goal should
also be called on the subprojects.
-->
<j:if test="${type == 'master'}">
<attainGoal name="multiproject:goal">
<j:set var="goal" value="eclipse"/>
</attainGoal>
</j:if>
</goal>
This goal is generic and can thus be put in 'master' projects or subprojects,
so my intent is satisfied: minimize custom scripting in maven.xml and if
scripting is really necessary, make it as generic as possible. On the other
hand, I think it would be easy to create a goal multiproject:run-goal-on-all in
the maven multiproject plugin that is similar to multiproject:goal but that can
run the goal on the parent project as well. This would avoid having to write a
custom script maven.xml.
Regards,
Davy Toch
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