Maven Project Structure with Multiple Modules

Question

I am somewhat new to the Maven project structure. I am creating a project this is going have two jars. Neither jar is dependent on each other, however, they will use some of the same libraries and there are two helper classes I created (one for logging) that would be used in both.

I was following this guide as far as project structure goes: http://maven.apache.org/guides/introduction/introduction-to-the-standard-directory-layout.html

My current project only has one module. I am using the IntelliJ IDE to create my build.xml (using ANT) to create my Jars. The IntelliJ build.xml, however, did not work off the bat and I had to do some manual editing to have it build both jars. I believe this would be solved if each jar was in it's own module. Also, according to the following, it seems they should be anyway http://www.jetbrains.com/idea/webhelp/module.html

This is where I am a little confused. If I do create a second module for my second jar, how do I deal with classes that are shared by both modules? Whenever I go to create a new module , IntelliJ gives the new module it's own src/ path.

As I said, I am new to the Maven project structure. I am also fairly new to ant and building jars using a build.xml. If I am completely on the wrong path please let me know so I can fix this problem early.

Thanks ahead of time.

Not a complete answer, so using a comment: What we do is have each module be its own maven project. Common code will be put in separate modules. And the projects/modules using them will have the needed modules as dependencies in their pom.xml file. — Matsemann, Aug 12 '13 at 12:47

Evgeniy Dorofeev · Accepted Answer · 2013-08-13T02:56:35.513

Create a multi-module project (x) which contains a pom.xml with packaging = pom

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>test</groupId>
  <artifactId>x</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>pom</packaging>
  <modules>
    <module>x1</module>
    <module>x2</module>
  </modules>
</project>

and 2 regular (jar) projects (x1 and x2). This is how the project structure should look like

x
  x1
    ...
    pom.xml
  x2
    ...
    pom.xml
pom.xml

The main project pom should contain dependencies common to both modules. Nested projects poms should have a reference to the parent.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>test</groupId>
    <artifactId>x</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </parent>
  <artifactId>x1</artifactId>
</project>

See more here http://maven.apache.org/guides/mini/guide-multiple-modules.html

score 2 · Answer 2 · answered Aug 12 '13 at 13:05

If you are going to do things the maven way you should remember that each (maven-)project only builds one artifact. So if you want to build two jars you will need two maven-projects (p1,p2) each with their own pom.xml.

If you got some classes that are used by both of these projects they will have to go to their own maven-project as well to build their own module-jar (p3). p3 will then be included in p1 and p2 as a dependency.

To build these jarrs in one go you could resort to the module-layout suggested by Evgeniy Dorofeev

Maven Project Structure with Multiple Modules

2 Answers2