Maven multi-module project in eclipse

Learn how to create multi module maven project in eclipse IDE. In this maven tutorial, we will learn to create nested maven projects in eclipse.

1. Create multi module maven project

Let’s create a maven project having modules packaging ear, war and jar types. We are creating the structure of an enterprise application where application will be deployed to applications servers (e.g. weblogic, websphere) as an EAR (Enterprise Application aRchive) file.

This EAR will contain one (or many) WAR (Web Application Resource) files and each war will contain the service project which has common code to all war files and packaging type in JAR (Java ARchive).

Projects Relationship

1.1. Create parent project – packaging type ‘pom’

Create a new maven project in eclipse. Set it’s packaging type to ‘pom‘.

Create new maven project

Fill maven group id and artifact id

Change packaging jar to pom

1.2. Create maven module – packaging type ‘ear’

Create a new maven module in the parent project. Change its packaging type to 'ear'. This module can have maven ear plugin which will ultimately build the ear file to be deployed on servers.

Create new maven module

Add Module Name

Fill archetype details

1.3. Create maven modules – packaging type ‘war’ and ‘jar’

Similar to ear module, create two more modules for war file and service jar file. Change their packaging respectively and add maven plugins.

1.4. Final result

Now observe the final project structure in eclipse and verify the pom.xml files for all projects.

pom.xml - Parent project

<?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>com.howtodoinjava.app</groupId>     <artifactId>HelloWorldApp</artifactId>     <version>0.0.1-SNAPSHOT</version>     <packaging>pom</packaging>       <name>HelloWorldApp</name>     <url>http://maven.apache.org</url>       <properties>         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>         <maven.compiler.source>1.8</maven.compiler.source>         <maven.compiler.target>1.8</maven.compiler.target>     </properties>       <modules>         <module>web</module>         <module>service</module>         <module>ear</module>     </modules> </project>

pom.xml - Ear project

<?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>com.howtodoinjava.app</groupId>         <artifactId>HelloWorldApp</artifactId>         <version>0.0.1-SNAPSHOT</version>     </parent>     <artifactId>ear</artifactId>     <name>ear</name>     <packaging>ear</packaging>     <properties>         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>     </properties>     <dependencies>         <dependency>             <groupId>com.howtodoinjava.app</groupId>             <artifactId>web</artifactId>             <version>0.0.1-SNAPSHOT</version>             <type>war</type>         </dependency>     </dependencies>     <build>         <pluginManagement>         <plugins>         <plugin>             <groupId>org.apache.maven.plugins</groupId>             <artifactId>maven-ear-plugin</artifactId>             <version>3.0.1</version>             <configuration>                 <modules>                     <webModule>                         <groupId>com.howtodoinjava.app</groupId>                         <artifactId>web</artifactId>                         <uri>web-0.0.1-SNAPSHOT.war</uri>                         <!-- Set custom context root -->                         <contextRoot>/application</contextRoot>                     </webModule>                 </modules>             </configuration>         </plugin>         </plugins>         </pluginManagement>     </build> </project>

pom.xml - War project

<?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>com.howtodoinjava.app</groupId>         <artifactId>HelloWorldApp</artifactId>         <version>0.0.1-SNAPSHOT</version>     </parent>     <groupId>com.howtodoinjava.app</groupId>     <artifactId>web</artifactId>     <version>0.0.1-SNAPSHOT</version>     <name>web</name>     <url>http://maven.apache.org</url>     <packaging>war</packaging>     <properties>         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>     </properties>     <dependencies>         <dependency>             <groupId>com.howtodoinjava.app</groupId>             <artifactId>service</artifactId>             <version>0.0.1-SNAPSHOT</version>         </dependency>     </dependencies> </project>

pom.xml - Jar project

<?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>com.howtodoinjava.app</groupId>         <artifactId>HelloWorldApp</artifactId>         <version>0.0.1-SNAPSHOT</version>     </parent>     <groupId>com.howtodoinjava.app</groupId>     <artifactId>service</artifactId>     <version>0.0.1-SNAPSHOT</version>     <name>service</name>     <url>http://maven.apache.org</url>     <packaging>jar</packaging>     <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>

To build the projects, run $mvn clean install command from console.

Console

E:\devsetup\workspacetemp\HelloWorldApp>mvn clean install   [INFO] Scanning for projects... [INFO] ------------------------------------------------------------------------ [INFO] Reactor Build Order: [INFO] [INFO] HelloWorldApp                                                      [pom] [INFO] service                                                            [jar] [INFO] web                                                                [war] [INFO] ear                                                                [ear] [INFO] ... ... [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ service --- [WARNING] JAR will be empty - no content was marked for inclusion! [INFO] Building jar: E:\devsetup\workspacetemp\HelloWorldApp\service\target\service-0.0.1-SNAPSHOT.jar [INFO] ... ... [INFO] Packaging webapp [INFO] Assembling webapp [web] in [E:\devsetup\workspacetemp\HelloWorldApp\web\target\web-0.0.1-SNAPSHOT] [INFO] Processing war project [INFO] Copying webapp resources [E:\devsetup\workspacetemp\HelloWorldApp\web\src\main\webapp] [INFO] Webapp assembled in [47 msecs] [INFO] Building war: E:\devsetup\workspacetemp\HelloWorldApp\web\target\web-0.0.1-SNAPSHOT.war [INFO] WEB-INF\web.xml already added, skipping [INFO] ... ... [INFO] [INFO] --- maven-ear-plugin:3.0.1:ear (default-ear) @ ear --- [INFO] Copying artifact [war:com.howtodoinjava.app:web:0.0.1-SNAPSHOT] to [web-0.0.1-SNAPSHOT.war] [INFO] Copy ear sources to E:\devsetup\workspacetemp\HelloWorldApp\ear\target\ear-0.0.1-SNAPSHOT [INFO] Building jar: E:\devsetup\workspacetemp\HelloWorldApp\ear\target\ear-0.0.1-SNAPSHOT.ear [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary: [INFO] [INFO] HelloWorldApp 0.0.1-SNAPSHOT ....................... SUCCESS [  0.328 s] [INFO] service ............................................ SUCCESS [  0.839 s] [INFO] web ................................................ SUCCESS [  0.838 s] [INFO] ear 0.0.1-SNAPSHOT ................................. SUCCESS [  0.588 s] [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2.749 s [INFO] Finished at: 2018-11-18T15:04:52+05:30 [INFO] ------------------------------------------------------------------------

The build generates an ear file with name ear-0.0.1-SNAPSHOT.ear. Feel free to change the name of projects and generated packages as per your need.

2. FAQs

2.1. GroupId is duplicate of parent groupId

Maven child projects inherit properties from parent project. If either group id or version id is same as parent project for any maven module/project, then we can simply remove this entry.

Remove duplicate entries

2.2. Artifact is not a dependency of the project

we may face this error when have added the module dependency (war) without specifying the type attribute.

Module type attribute