Is there a way to build a project for different client with the same base but with modularity for some feature that would be discovered at runtime?

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I'm used to using the E4 Eclipse framework to build desktop applications and now I would like to migrate to a simple maven project.

In the Eclipse platform with OSGi, there is a notion of bundle, feature and product.

When I want to build my project for client A, I have a file A.product describing all the dependencies. For client B, I have B.product and so on.

Of course, my software shares the same base, but if a client wants a new feature (like a plugin) I have to add it to my product file, and the new feature will be discovered at runtime and present to my software.

In maven, I don't find a good way to do the same things, because there is only one pom.xml describing the whole project. How can I introduce modularisation for plugin discovered at runtime?
Should I have multiple POM for each client? Should I use the profile to do that? I tried but I was not easy to manage.

Is there another maven good way to do it, and to manage the variability easily?

quarkus maven java
1 Answers

Re „And (maybe) another Pom.xml (or profile ?)“ in one of your comments to the question:

One of Maven's principles is: one project (declared in a POM), one resulting (main) artifact (JAR, WAR, ...). („main“ since there can be accompanying artifacts like ...-sources.jar, ...-javadoc.jar, ...-jar-with-dependencies.jar, ....zip, ...)

Maven POMs are of declarative nature. That means, there are no (imperative) ifs to skip declarations on occasion and you also can't add/remove declaration (XML) elements during build (you "just" can add/change element text contents via properties). (There are plugins with a <skip>false|true parameter, which can be set/overridden with a property, but that's not a general rule and therefore there are not many of them.)

Profiles are a way to overcome this no-if-principle. With them you can activate ("inject") declarations which set or override existing declarations at build time via various profile activation methods.

Regarding your comment after removing the osgi tag, I'm going to update this answer later. In the meantime you can have a look at my answer to Maven: Lifecycle vs. Phase vs. Plugin vs. Goal.

UPDATE

+- jojal-main
   +- pom.xml   ... contains declarations common for all of your projects
   +- base-main
      +- pom.xml   ... contains declarations common for all base projects
      +- A
         +- src/main/java/your/package/Plugin.java
         +- pom.xml
      +- B
         +- src/main/java/your/package/ClassA.java   ... implements Plugin
         +- pom.xml
      +- C
         +- src/main/java/your/package/ClassB.java   ... implements Plugin
         +- pom.xml
   +- product-main
      +- pom.xml   ... contains declarations common for all product projects
      +- product1
         +- src/main/java/your/package/Product1.java   ... references A & B
         + pom.xml
      +- product2
         +- src/main/java/your/package/Product2.java   ... references A & C
         +- pom.xml
      +- product3
         +- src/main/java/your/package/Product3.java  ... references A & B & C
         +- pom.xml

jojal main POM

<project ...>
  ...

  <groupId>name.jojal</groupId>
  <artifactId>jojal-main</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>pom</packaging>  <!-- different to the default 'jar'[1] -->

  <modules>  <!-- to build projects in sub-dirs at once[2] -->
    <module>base-main</module>
    <module>product-main</module>
  </modules>

  ... declarations common for all of your projects like dependencies for unit testing, logging etc. ..

<project>

[1] POM Reference, Packaging
[2] POM Reference, Aggregation

Base main POM

<project ...>
  ...

  <parent>   <!-- declarations are inherited from this parent POM[3] -->
    <groupId>name.jojal</groupId>
    <artifactId>jojal-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>jojal-base-main</artifactId>  <!-- <groupId>, <version> can be omitted if the same as in parent -->
  <packaging>pom</packaging>

  <modules>
    <module>A</module>
    <module>B</module>
    <module>C</module>
  </modules>

  ... declarations common for all base projects ...

<project>

[3] POM Reference, Inheritance

A POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal.base</groupId>
    <artifactId>jojal-base-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>
 
  <artifactId>project-a</artifactId>

<project>

B POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal.base</groupId>
    <artifactId>jojal-base-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>project-b</artifactId>

  <dependencies>
    <dependency>
      <groupId>name.jojal.base</groupId>
      <artifactId>project-a</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>

<project>

C POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal.base</groupId>
    <artifactId>jojal-base-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>
 
  <artifactId>project-c</artifactId>

  <dependencies>
    <dependency>
      <groupId>name.jojal.base</groupId>
      <artifactId>project-a</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>

<project>

Product main POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal</groupId>
    <artifactId>jojal-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>jojal-product-main</artifactId>
  <packaging>pom</packaging>

  <modules>
    <module>product1</module>
    <module>product2</module>
    <module>product3</module>
  </modules>

  ... declarations common for all product projects ...

<project>

Product 1 POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal.product</groupId>
    <artifactId>jojal-product-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>product-1</artifactId>

  <dependencies>
    <dependency>
      <groupId>name.jojal.base</groupId>
      <artifactId>project-b</artifactId>  <!-- project-a is resolved automatically by Maven
                                               as a transitive dependency[4] -->
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>

<project>

[4] POM Reference, Dependencies

Product 2 POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal.product</groupId>
    <artifactId>jojal-product-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>product-2</artifactId>

  <dependencies>
    <dependency>
      <groupId>name.jojal.base</groupId>
      <artifactId>project-c</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>

<project>

Product 3 POM

<project ...>
  ...

  <parent>
    <groupId>name.jojal.product</groupId>
    <artifactId>jojal-product-main</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>product-3</artifactId>

  <dependencies>

    <dependency>
      <groupId>name.jojal.base</groupId>
      <artifactId>project-b</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>

    <dependency>
      <groupId>name.jojal.base</groupId>
      <artifactId>project-c</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>

  </dependencies>

<project>

[Please note: Not tested in real, typos possible]

user_17447740
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