Question

I have a fairly simple maven-ized Java project, but am having trouble getting my head around it.

My parent module defines a lot of Java classes (and dependencies) that I expect to be useful for several child modules. One of the child modules is dedicated to deploying a web app, so it needs a few extra classes (the servlets) plus everything from the parent module.

The file structure looks like this

 - parent
   - src
   - pom.xml
   - child
     - src
     - pom.xml

My parent pom looks like this:

<project>
  <groupId>my.group</groupId>
  <artifactId>parent</artifactId>
  <version>0.0.1</version>
  <packaging>pom</packaging>

  ...

  <modules>
    <module>child</module>
  </modules>
</project> 

And the child looks like this:

<project>
  <artifactId>child</artifactId>
  <packaging>war</packaging>
  <parent>
    <artifactId>parent</artifactId>
    <groupId>my.group</groupId>
    <version>0.0.1</version>
  </parent>

  ...

</project>

Is this all I need to have the child know about the classes and dependencies defined in parent? It doesn’t seem to be: eclipse gives compile errors, and running mvn clean package from parent folder or child folder results “cannot find symbol” messages any time a class from parent is mentioned.

What am I doing wrong?

Answer 1

I’d change the structure of your project like this:

• parent (pom)
  • core (jar, with all the classes that used to be in parent)
  • child (war, depends on core)

Parent:

<project>
  <groupId>my.group</groupId>
  <artifactId>parent</artifactId>
  <version>0.0.1</version>
  <packaging>pom</packaging>

  <modules>
    <module>core</module>
    <module>child</module>
    <!-- possibly more modules... -->
  </modules>
</project>

Core:

<project>
  <parent>
    <groupId>my.group</groupId>
    <artifactId>parent</artifactId>
    <version>0.0.1</version>
  </parent>
  <artifactId>core</artifactId>
  <packaging>jar</packaging>
</project>

Child:

<project>
  <parent>
    <groupId>my.group</groupId>
    <artifactId>parent</artifactId>
    <version>0.0.1</version>
  </parent>
  <artifactId>module1</artifactId>
  <packaging>war</packaging>

  <dependencies>
    <dependency>
      <groupId>my.group</groupId>
      <artifactId>core</artifactId>
      <version>${project.version}</version>
    </dependency>
  </dependencies>
</project>