I am wondering if there is a way to run a Maven subproject alone. I mean, in several code samples you can find a group of maven projects with a common parent. There is a way to replace parent in order to be able to run just a subproject.
Lets suppose this repository https://github.com/in28minutes/spring-boot-examples
There is way to run just spring-boot-tutorial-soap-web-services/ project?
Thanks in advance.
maven projects are identified by pom.xml and you can run any maven project individually. (Any maven goal).
cd into_a_maven_project(identified by pom.xml).
mvn install(this will run install phase for the project).
There are several relationships among maven projects.
Parent-child
Submodule
Dependency
Parent-child: This relationship is used in defining a pom. For instance, When a set of pom shares a lot, you can define a parent pom(parent maven project) and reference from the child project. (reference is done from child to parent)
When you run child project, the parent project is used only to inherit the pom(copy the content of parent pom). Child pom overrides the configuration in parent pom.(child pom contains little because of the fact that required configurations copied from the parent pom)
Submodule: This relationship is used when it makes sense to build multiple projects together. In this case, you run build in the project referencing submodules. (This is not a parent child relationships, the pom is not inherited if the project is not also a parent). The result is that the submodule projects become part of the build. (The order of the build is determined by dependencies between them)
Dependency: This relationship is used when the code in a project depended by your project. The build order is calculated using this relationship.
Related
I have a maven Mojo plugin that I'd like to execute only in child pom, but not in the current pom or grandchildren poms. My plugin runs at compile time and essentially reads files, and for my use case if it runs in the child pom, it is redundant to run in grandchildren poms.
For example, I have a maven Mojo plugin that gets called by a parent pom file ParentFile. This pom file is inherited in other repositories, which I don't have write access to. In these repositories, there is a root module with a pom file ChildFile, whose parent is ParentFile. There are also other submodules in the repository that contain pom files (GrandchildrenFiles) whose parent is ChildFile.
I would like to execute my Mojo plugin from ChildFile, but not from GrandchildrenFiles or ParentFile. Is there a way for me to do this without write access to the repositories containing ChildFile and GrandchildrenFiles?
You probably cannot stop your plugin from being executed, but you could check, as first step in your plugin, if your parent is the parent you expected. For that, you can use project.getParent().
If not, you just skip the rest of the execution.
I have created a maven goal that outputs a dependency tree for a given maven project to a YAML file. Using the m2eclipse plugin for Eclipse Photon.
Currently when I run the goal against a parent project (using type pom when setting up dependency), the only dependency returned is on the pom for the specific parent. Is there any way to prevent me needing to run this goal against all of the projects underneath the parent?
Might need a little more information on this, but are your children poms of the parent specified as modules within the parent pom?
Example:
<parentPom>
<modules>
<module>/path/to/childA</module>
</modules>
</parentPom>
I have Maven project with multiple submodules. One of these submodules, let's say submodule X depends on all other submodules, as it is Maven Plugin that integrates everything else.
Now I want to use this Maven Plugin during verify stage in my parent POM to do real run of it over entire project (kind of eating own dogfood).
Unfortunatelly I'm getting error:
The projects in the reactor contain a cyclic reference
So how can I make such dogfood integration test for a Maven Plugin submodule?
I would review aggregation and inheritance: they are indeed two different concepts in Maven often used in combination but which can however be used in a complete separated manner as well.
In this case, your plugin submodule is certainly defined as a module in the aggregator pom (that is, it is a submodule). But I also presume the plugin submodule also has as parent pom the aggregator pom as well (that is, the aggregator pom is also the parent pom, which is a normal approach, but not always required).
Is the latter required? You could keep on having the multi-module/aggregator approach without necessarely having the aggregator as parent of the plugin submodule. As such, the plugin subModule would still be a module of the aggregator pom but it would not have as a parent the aggregator pom, decoupling it from it and as such breaking the cyclic dependencies.
Possible drawback: in the aggregator pom you were also defining common things (dependencies management, properties) required also in the plugin submodule. If the case, you would then need to duplicate/review these common settings only for the concerned submodule.
Small suggestion from my side. Cyclic means you have some transitive dependency in your modules. Can please check the dependency tree of your modules and resolve the circular dependency first.
Let's say I have a maven project which has some maven modules inside.
My main module depends on the other modules, so when I compile the main module they should be compiled together.
The question is, how to add these modules as dependencies to the main module?
I know if I have a custom lib that I want to use with maven, let's say a utilities project, I have to compile the jar of the project, do a mvn install:install-file on it to install it on the local repository and then add it to the pom.xml.
Do I have to do this with all my modules and add the dependency to the pom.xml on my main module? Because if it should be done like this, there will be a lot of work to do when changing code on the other modules.
What is the best practice to use avoid the trouble of compiling/installing the modules to local repository?
The question is, how to add these modules as dependencies to the main module?
The same way you add any other dependency to your maven project. By adding group id, artifact id and version to <dependency> element
Do I have to do this with all my modules and add the dependency to the pom.xml on my main module?
If your main module depends on some module A then only the pom of the main module should contain dependency declaration towards module A. You do that for all the dependencies of your module.
I don't know what you mean by "a lot of work when changing the code on other modules". Maven has nothing to do with code changes, it just builds the projects whatever they look like at the given moment...
What is the best practice to use avoid the trouble of compiling/installing the modules to local repository?
Any project that you invoke mvn install on gets built and it's jar copied to local repository. That's all you need to do to get the jar into the repo. This will also put all the dependent jars, if available, into the local repo.
As for best practices for multi module projects:
If your parent project (the one that has modules inside) has <modules> section that lists the modules of your application, and modules are in subdirectories of your parent project, then you simply mvn install (or whatever you want to do) the parent project and that will cause all the modules to be built in order defined by declared dependencies between them. That means that if your main module has dependency on module A, then module A will be built before the main module. This way you can build and install all your modules with one command. On the other hand this approach makes more tight coupling between modules which is not desired in some cases, so it depends on your use case whether it is a good approach or not.
I'm just curious, what happens if there are used both inheritance and aggregation in the same maven application?
This is the application structure:
my-project-app
my-project-jar
my-project-war
Now, in app's pom.xml, I declare jar and war projects as modules, and in the same time the the poms from both modules declare the app pom as their parent. It is create some kind of redundancy here, isn't it?
What is the best solution for this case?
It's not redundant. They both do different things.
If you use aggregation (define <modules>), you just say which projects have to be built, and its package type is pom.
If you inherit (define <parent>), you'll inherit the parent pom's preferences.
See:
Inheritance and aggregation create a nice dynamic to control builds through a single, high-level POM. You will often see projects that are both parents and aggregators. For example, the entire maven core runs through a single base POM org.apache.maven:maven, so building the Maven project can be executed by a single command: mvn compile. However, although both POM projects, an aggregator project and a parent project are not one in the same and should not be confused. A POM project may be inherited from - but does not necessarily have - any modules that it aggregates. Conversely, a POM project may aggregate projects that do not inherit from it.
More infos here.