Per Maven documentation Maven will only look in local and remote repos for a parent pom after it fails to find it locally. The best solution I've found to dummy this out is by adding
<relativePath>.</relativePath>
which is obviously a kludge and produces warnings (as it well should). Maven seems to be like file-system coupling when dealing with parent modules and multi-module projects so this is the only way I see to have both of those co-exist without something that feels obviously wrong (e.g. inheriting from a filesystem child).
You reference the parent pom using the tag:
<parent>
<groupId>com.mycompany</groupId>
<artifactId>my-parentpom</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
You must install the parent pom into your local repo using the mvn install -N command from the directory that contains the parent POM.
Related
Maven install knows all the artifacts generated by a build, and will push them locally.
Installs the project's main artifact, and any other artifacts attached by other plugins in the lifecycle, to the local repository.
the help plugin probably supports this, but not sure of right expression
# has all the pieces (artifact, version, type) but is it fair to assume filename will always be that combo?
mvn help:evaluate -Dexpression=project.artifact
Is there any way to get that list of paths from a maven command?
I want to generate a list of specific artifacts to persist as artifact results in a build process, without publishing to a maven repo.
Artifact paths in Maven repository will follow the following formula by default:
groupId is broken into folders using the full stops as delimiter, then artifactId and version form the last two folders
filename of the artifact consists of artifactId and version, type is defined by packaging
So, let's say you have a multi-module project with main pom.xml:
<groupId>com.foobar.my.business</group>
<artifactId>myApp</artifactId>
<version>1.0-SNAPSHOT</version>
And it has two submodules, first is web module that creates a REST endpoint:
<parent>
<groupId>com.foobar.my.business</group>
<artifactId>myApp</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>myApp-web</artifactId>
<packaging>war</packaging>
Second one is persistence layer:
<parent>
<groupId>com.foobar.my.business</group>
<artifactId>myApp</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>myApp-persistence</artifactId>
<packaging>jar</packaging>
Let's say your local repository is found from ~/.m2/repository. Then your artifacts will be saved in local repository at:
~/.m2/repository/com/foobar/my/business/myapp/1.0-SNAPSHOT/myapp-1.0-SNAPSHOT.pom
~/.m2/repository/com/foobar/my/business/myapp-web/1.0-SNAPSHOT/myapp-web-1.0-SNAPSHOT.pom
~/.m2/repository/com/foobar/my/business/myapp-web/1.0-SNAPSHOT/myapp-web-1.0-SNAPSHOT.war
~/.m2/repository/com/foobar/my/business/myapp-persistence/1.0-SNAPSHOT/myapp-persistence-1.0-SNAPSHOT.pom
~/.m2/repository/com/foobar/my/business/myapp-persistence/1.0-SNAPSHOT/myapp-persistence-1.0-SNAPSHOT.jar
An artifact's final build name and the local repository location can be tinkered with. But you can use the following expressions to check those:
${settings.localRepository} will return path to local repository.
${project.build.finalName} will return final build artifact name.
To get this list in almost the correct format, you can run:
On Windows mvn -q exec:exec -Dexec.executable="cmd" -Dexec.args="/C echo ${settings.localRepository}\${project.groupId}\${project.artifactId}\${project.version}\${project.build.finalName}.${project.packaging}"
On POSIX mvn -q exec:exec -Dexec.executable='echo' -Dexec.args='${settings.localRepository}/${project.groupId}/${project.artifactId}/${project.version}/${project.build.finalName}.${project.packaging}'
Then you just have to fix the full stops in groupId.
There is also a mvn dependency:build-classpath command which will show the location of each dependency on the file system that can come in handy sometimes.
with maven 3 i have a parent project at 'C:/travail/parent'.
I have several child-projects who, for various reasons, can change locations.
To make a war, the relativePath tag must be set.
<parent>
<groupId>framework.parent</groupId>
<artifactId>parent</artifactId>
<version>1.0.0-SNAPSHOT</version>
<relativePath>C:/Travail/parent/pom.xml</relativePath>
</parent>
Question: How can I put an absolute path for the parent? The following doesn't work.
<relativePath>/C:/Travail/parent/pom.xml</relativePath>
You cannot use an absolute path for your parent pom, the name itself of the configuration entry is quite self explanatory (relative path).
From the official Maven model documentation for this element:
The relative path of the parent pom.xml file within the check out. If not specified, it defaults to ../pom.xml. Maven looks for the parent POM first in this location on the filesystem, then the local repository, and lastly in the remote repo. relativePath allows you to select a different location, for example when your structure is flat, or deeper without an intermediate parent POM. However, the group ID, artifact ID and version are still required, and must match the file in the location given or it will revert to the repository for the POM. This feature is only for enhancing the development in a local checkout of that project. Set the value to an empty string in case you want to disable the feature and always resolve the parent POM from the repositories.
Default value is: ../pom.xml.
You can't even use a shortcut or symbolic link for the same, distributed together with each and every module and pointing at the absolute file location, it would not work (and you shouldn't use such a trick anyway, even if it was going to work).
You can't even use a property as value placeholder of the relativePath element. Something like:
<parent>
<groupId>framework.parent</groupId>
<artifactId>parent</artifactId>
<version>1.0.0-SNAPSHOT</version>
<relativePath>${path.to.parent}</relativePath>
</parent>
And try to inject it at build time like:
mvn clean install -Dpath.to.parent=C:/somewhere/pom.xml
Would simply not work, as also documented by the following Maven tickets:
MNG-2569: Expressions not evaluated inside
MNG-624: automatic parent versioning
The only reasonable use case for this configuration entry is, as mentioned in the official documentation, for flat-structured multi-module projects, where modules and parent project are located at the same directory level.
Otherwise, and more suitable for your use case, you should provide the parent pom as part of the shared Maven repository (if any) or require a maven install (so that it will be available in the local maven cache) of the parent project upfront for any new version before any required maven action on the children/module projects.
What's the best structure for a (multi-module) Maven project which should build "in the wild" without any Maven repository manager and can easily build within my organization where deployments should happen to my Maven repository manager?
Ideally, I would have two different paren POMs for each situation.
But unfortunately, I can't use a Maven property to pass the correct value for each situation, because the property expression in the parent POM reference doesn't get interpolated, if I try something like
<parent>
<groupId>org.example</groupId>
<artifactId>${root.pom}</artifactId>
<version>1.0-SNAPSHOT</version>
<relativePath/>
</parent>
...
<properties>
<root.pom>wild-parent</root.pom>
</properties>
Added a minimalistic project which shows a crude approach to solve this by patching the parent POM via sed.
This response on the maven-users mailing list pointed me in the direction to use Maven properties to pass in the in-house specifics.
I updated the example project.
E.g.:
<parent>
<groupId>mycompany.trade.com</groupId>
<artifactId>mycompany.trade.</artifactId>
<version>1.1.1.0-SNAPSHOT</version>
</parent>
Does it mean that Maven will search for parent pom?
If yes, where, in which order? May be in folder up 1 level? Or in local repository or in repo?
Yes, maven reads the parent POM from your local repository (or proxies like nexus) and creates an 'effective POM' by merging the information from parent and module POM.
See also Introduction to the POM
One reason to use a parent is that you have a central place to store information about versions
of artifacts, compiler-settings etc. that should be used in all modules.
The common dependencies,Properties,constants etc can be definded in central parent project pom.xml
The main important thing is the parent project cannot be distributed and it looks quite similar to a regular "pom.xml" except that it also has a packaging tag
<groupId>com.company.demo</groupId>
<artifactId>MavenInheritance</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>pom</packaging>
The child now able to inherit this using
<parent>
<groupId>com.company.demo</groupId>
<artifactId>MavenInheritance</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
As the name suggests, we can point out a parent pom.xml file for the current pom.xml file. Doing so, dependencies, properties, constants and many more defined at the parent pom.xml file also get merged with the current pom.xml (child pom.xml) file. Say you have a parent tag in your projects pom.xml that looks like below:
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.8.RELEASE</version>
</parent>
Then maven reads that parent POM from your local repository (or from repository managers like sonatype, jfrog, etc that you have configured) and creates a Resultant POM by combining the parent POM and your module’s POM.
To see the combined result use the following mvn command:
mvn help:effective-pom
This is the practice that is used in multi-modules projects where we need to inherit the dependencies from the parent projects.
I have a maven project - it is a plugin for jenkins. It's parent should be a:
<parent>
<groupId>org.jenkins-ci.plugins</groupId>
<artifactId>plugin</artifactId>
<version>1.414</version>
</parent>
But at the same time this plugin can be also used for hudson, without changing any line of code. But the parent project for it should be:
<parent>
<groupId>org.jvnet.hudson.plugins</groupId>
<artifactId>hudson-plugin-parent</artifactId>
<version>2.0.1</version>
</parent>
Can I specify 2 different profiles for that and use them to build plugin for jenkins or hudson accordingly? So that I call something like that:
mvn package -P jenkins
or
mvn package -P hudson
I have tried to specify properties in profiles, but those are not replaced by their values inside the <parent> tag. So is there any other possibility to build plugin for both, but with as much as possible common code and files?
Added: So, if I cannot do that, what should I do then? How to refactor? What the new structure should be?
As already mentioned, this is not possible.
Also, it is not possible to set a property for the parent's version as the interpolation for that happens a lot earlier than the handling of the profiles.
I would suggest that you create a masterbuild project as follows:
master
|-plugin-jenkins
|-plugin-hudson
|-plugin-assembly
The master should build all three as usual. However, in the assembly, you could add each of the two plugins as dependencies in separate profiles. And... each of these plugins can have the parent you like.
This is obviously somewhat a deviation from the Maven convention, but I believe it is a solution to your problem.
It's not possible because the tag "parent" is not available in the profiles section of the pom.
Currently we decided to stick with 1 repository and 2 separate pom.xml files, giving maven key which pom.xml use to build the project.
mvn package -f pom-jenkins.xml
mvn package -f pom-hudson.xml
No you cannot do that. you will have to refactor somehow to avoid the necessity.
As mentioned already not possible. I would suggest to make separate projects for jenkins plugin and hudson plugin. I assume that in not that far future that will not work anymore cause Hudons and Jenkins will diverge.
In general, you should be able to set the {group,artifact}Id and version of the parent POM via Java System Properties or Environment Variables, but it seems there is a Bug in Maven which will only be fixed in 4.x:
https://issues.apache.org/jira/browse/MNG-624
Another solution is to delegate the inclusion of the parent POM to your own parent POMs which you reference in the relativePath element, and change the content of the target e.g. via a symlink or cp command.
So in the main POM you would write:
<parent>
<groupId>org.mycompany.project</groupId>
<artifactId>foo-artifact</artifactId>
<version>1.0.0</version>
<relativePath>./my-parent.pom</relativePath>
</parent>
And in my-parent-jenkins you would just put:
<groupId>org.mycompany.project</groupId>
<artifactId>foo-artifact</artifactId>
<version>1.0.0</version>
<parent>
<groupId>org.jenkins-ci.plugins</groupId>
<artifactId>plugin</artifactId>
<version>1.414</version>
</parent>
The same project information with the block for hudson you put in my-parent-hudson.pom.
No you can either use
ln -s my-parent-jenkins.pom my-parent.pom
or
ln -s my-parent-hudson.pom my-parent.pom
to include the respective parent POM without the need to maintain two different main POM files for your project.
In case POM does not exist at the place referenced in relativePath, Maven will look up the POM in the remote repository[1], which is also an easy way to overwrite a parent POM locally.
[1] http://maven.apache.org/components/ref/3.3.9/maven-model/maven.html#class_parent