Meaning of parent tag in Maven

Question

I created my project with structure same as in next snippet of code.

|-- modP

|   |-- pom.xml

|   |-- src

|   |   |-- main

|   |     `-- java

|   |         `-- com

|   |             `-- myorg

|   |                 `-- myapp

|   |                     `-- modP

|   |                         `-- AppP.java

|-- modC1

|   |-- pom.xml

|   |-- src

|   |   |-- main

|   |     `-- java

|   |         `-- com

|   |             `-- myorg

|   |                 `-- myapp

|   |                     `-- modC

|   |                         `-- AppM.java

|-- modC2

|   |-- pom.xml

|   |-- src

        |-- main

          `-- java

              `-- com

                  `-- myorg

                      `-- myapp

                          `-- modC2

                              `-- AppN.java

My pom.xml for modP is:

<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>com.myorg.myapp</groupId>

  <artifactId>modP</artifactId>

  <version>0.0.1-SNAPSHOT</version>

  <packaging>pom</packaging>



  <name>modP</name>

  <url>http://maven.apache.org</url>



  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

  </properties>



  <dependencies>

    <dependency>

      <groupId>junit</groupId>

      <artifactId>junit</artifactId>

      <version>3.8.1</version>

          <scope>test</scope>

    </dependency>

  </dependencies>

</project>

My pom.xml for C1 is :

<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">

<parent>

    <artifactId>modP</artifactId>

    <groupId>com.myorg.myapp</groupId>

    <version>0.0.1-SNAPSHOT</version>

    <relativePath>.../modP/pom.xml</relativePath>

</parent>

<modelVersion>4.0.0</modelVersion>



  <groupId>com.myorg.myapp</groupId>

  <artifactId>modC1</artifactId>

  <packaging>jar</packaging>



  <name>modC1</name>

  <url>http://maven.apache.org</url>

</project>

And pom.xml for C2 is:

<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">

<parent>

    <artifactId>modP</artifactId>

    <groupId>com.myorg.myapp</groupId>

    <version>0.0.1-SNAPSHOT</version>

    <relativePath>.../modP/pom.xml</relativePath>

</parent>

<modelVersion>4.0.0</modelVersion>



  <groupId>com.myorg.myapp</groupId>

  <artifactId>modC2</artifactId>

  <packaging>jar</packaging>



  <name>modC2</name>

  <url>http://maven.apache.org</url>

</project>

My question is can I using such configuration reference AppP.java from ModP in AppC1.java and AppC2.java in ModC1 and ModC2.

I tried this and it looks like this doesn't works. Did I misunderstood meaning of parent tag in pom.xml? What I need to do in maven for such function?

I read a lot of documentation, but now I'm even more confused than before reading. :(

Every answer will be highly appreciated.

Thanks

Answer 1

Typically maven projects hierarchy is stored in hierarchical file system. Child projects are stored under parent, i.e. in your terms:

modP
    pom.xml
    modC1
        pom.xml
    modC2
        pom.xml

The sub projects may have their own children etc.

Each project except the higher-level one should contain definition like

<parent>
    <groupId>com.company</groupId>
    <artifactId>parent-artifact-id</artifactId>
    <version>1.0</version>
</parent>

Each parent module should hold list of modules:

<modules>
    <module>child1</module>     
    <module>child2</module>     
    <module>child3</module>     
</modules>

As far as I understand in your case you hold all 3 projects in the same directory but one of them is parent. It is possible but I think that your reference to parent's pom is wrong. Number of dots is 3 while should be 1:

<relativePath>.../modP/pom.xml</relativePath>

try this one:

<relativePath>../modP/pom.xml</relativePath>

Answer 2

Since ModP is a pom (packaging) project, it should not contain any Java code.