Question

I purchased the ‘Apache Maven 3 Cookbook’ and I’m trying to learn on adding dependencies to my maven projects.

my main project pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<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>net.srirangan.packt.maven</groupId>
<artifactId>TestModularApp</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>

<name>TestModularApp</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>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.2</version>
</dependency>
</dependencies>
<modules>
<module>ChildProject</module>
<module>MyWebApp</module>
</modules>
</project>

as you can see here the packaging in this project is set to "pom" because this is the parent project.. ( that’s all i know 🙂 )

and then I created a subproject with the following pom.xml:

<?xml version="1.0"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>net.srirangan.packt.maven</groupId>
    <artifactId>TestModularApp</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>
  <groupId>com.xpogames.childproject</groupId>
  <artifactId>ChildProject</artifactId>
  <version>1.0-SNAPSHOT</version>
  <name>ChildProject</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>
    <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    </dependency>
  </dependencies>
</project>

as you can see here i did not add a version property to the mysql-connect-java dependency because it supposed to inherit the version from the parent project. but for some reason, it doesn’t.

when I run mvn compile on that project i get an error that the dependencies.dependency.version property is missing.

any ideas what i’m doing wrong? how can I resolve the issue that i won’t need to specify versions in sub-projects too ?

thanks!

update

after watching Peter Lawrey’s answer and watching the example on the url he provided
I noticed that my main XML is missing the property <dependencyManagement> around the <dependencies>. once I added that property then I didn’t need to provide a version number in the sub-project.

Peter answer shows another method to achieve this goal.

thanks for everything!

Kfir

Answer 1

You inherit versions from the dependencies in the dependencyManagement section of your parent pom(s) and selectively include these in child poms.

In your case you don’t need to mention the dependency again as it already included from the parent. (As it is for JUnit)

BTW: I use JUnit 4.10 which I haven’t found any backward compatibility problems with.