Build a Multiple Module Project with Maven

Introduction
Model example
Create project MathLibrary
Create project MathWebApp
Create project MavenParent
Configure Maven the relationship between the Projects
Pack the modules

1. Introduction

This document is based on:

Eclipse 4.6 (NEON)

You are viewing the advanced Maven. If you are a beginner Maven. You should look at the documentation for beginners Maven (Maven Hello world) at:

Maven Tutorial for Beginners

2. Model example

This is the model example in this document.

The objective of the guidelines is:

How a module using other module in Maven
Packing multiple Module using Maven (output: jar, war).

MathWebApp: is a WebApp project
MathLibrary: is a library Project, contains utility classes used by MathWebApp.

MavenParent: will pack two projects above, it is a parent module. MavenParent will:

Packing MathLibary to a jar file
Packing MathWebApp to a file war.

3. Create project MathLibrary

File/New/Other...

This is a simple Project, so we don't need to select a Maven archetype.

Select:

Create a simple project (skip archetype selection)

Enter:

Group Id: org.o7planning
Artifact Id: MathLibrary
Packaging: jar

Skip parent module information.

Project is created.

Create class MathUtils:

MathUtils.java

package org.o7planning.mathutils;

public class MathUtils {

  public static int sum(int a, int b) {
      return a + b;
  }

}

4. Create project MathWebApp

File/New/Other..

Select maven-archetype-webapp archetype. Eclipse will create a Project Maven that has the structure of a web application.

Enter:

Group Id: org.o7planning
Artifact Id: MathWebApp
Version: 0.0.2-SNAPSHOT
Package: org.o7planning.mathwebapp

Here is a screenshot MathWebApp project has been created. You may see an error message somewhere on the Project, do not worry about it, cause you have not declared Servlet library.

Eclipse create this project structure may be wrong. You need to check out.

Open file pom.xml

Add:

<dependency>
 <groupId>javax.servlet</groupId>
 <artifactId>javax.servlet-api</artifactId>
 <version>3.1.0</version>
 <scope>provided</scope>
</dependency>

As illustrated below:

Now error has no longer exist:

Continue configure Maven, MathWebApp use MathLibrary:

<dependency>
   <groupId>org.o7planning</groupId>
   <artifactId>MathLibrary</artifactId>
   <version>0.0.1-SNAPSHOT</version>
</dependency>

MathWebApp/pom.xml

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.o7planning</groupId>
  <artifactId>MathWebApp</artifactId>
  <packaging>war</packaging>
  <version>0.0.2-SNAPSHOT</version>
  <name>MathWebApp Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
      <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>3.8.1</version>
          <scope>test</scope>
      </dependency>


      <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>3.1.0</version>
          <scope>provided</scope>
      </dependency>
     
      <dependency>
          <groupId>org.o7planning</groupId>
          <artifactId>MathLibrary</artifactId>
          <version>0.0.1-SNAPSHOT</version>
      </dependency>        
     
  </dependencies>
  <build>
      <finalName>MathWebApp</finalName>
  </build>
</project>

Edit file index.jsp using MathUtils, class in project MathLibrary.

index.jsp

<html>
<body>
<h2>Hello World!</h2>

<%

int a = 100;
int b = 200;

int c = org.o7planning.mathutils.MathUtils.sum(a,b);

out.println("<h2>"+ c+"</h2>");

%>

</body>
</html>

5. Create project MavenParent

Create a Common Java Project.

File/New/Other..

Right-click the newly created project MavenParent, and convert it to Maven Project.

Enter:

Group Id: org.o7planning
Artifact Id: MavenParent
Version: 1.0.0-SNAPSHOT
Packaging: pom

6. Configure Maven the relationship between the Projects

This image describes briefly the Maven relational configuration among Projects.

Open file pom.xml of 2 project MathLibrary & MathWebApp and add:

<parent>
   <groupId>org.o7planning</groupId>
   <artifactId>MavenParent</artifactId>
   <version>1.0.0-SNAPSHOT</version>
   <relativePath>../MavenParent/pom.xml</relativePath>
</parent>

Open pom.xml of MavenParent add:

<modules>
  <module>../MathLibrary</module>
  <module>../MathWebApp</module>
</modules>

MathLibrary/pom.xml

<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>org.o7planning</groupId>
 <artifactId>MathLibrary</artifactId>
 <version>0.0.1-SNAPSHOT</version>


 <parent>
     <groupId>org.o7planning</groupId>
     <artifactId>MavenParent</artifactId>
     <version>1.0.0-SNAPSHOT</version>
     <relativePath>../MavenParent/pom.xml</relativePath>
 </parent>

</project>

MathWebApp/pom.xml

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.o7planning</groupId>
  <artifactId>MathWebApp</artifactId>
  <packaging>war</packaging>
  <version>0.0.2-SNAPSHOT</version>
  <name>MathWebApp Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
      <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>3.8.1</version>
          <scope>test</scope>
      </dependency>


      <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>3.1.0</version>
          <scope>provided</scope>
      </dependency>

      <dependency>
          <groupId>org.o7planning</groupId>
          <artifactId>MathLibrary</artifactId>
          <version>0.0.1-SNAPSHOT</version>
      </dependency>

  </dependencies>

  <parent>
      <groupId>org.o7planning</groupId>
      <artifactId>MavenParent</artifactId>
      <version>1.0.0-SNAPSHOT</version>
      <relativePath>../MavenParent/pom.xml</relativePath>
  </parent>

  <build>
      <finalName>MathWebApp</finalName>
  </build>
</project>

MavenParent/pom.xml

<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>org.o7planning</groupId>
  <artifactId>MavenParent</artifactId>
  <version>1.0.0-SNAPSHOT</version>
  <packaging>pom</packaging>


  <modules>
      <module>../MathLibrary</module>
      <module>../MathWebApp</module>
  </modules>

</project>