How to build an executable jar from multi module maven project?

Question

I'm beginner with maven and do not understand many things. I can build simple executable jar, but how to build multimodule maven project into executable jar is magic for me. So, I have three projects. Parent:

<?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>org.example</groupId>     <artifactId>Test</artifactId>     <packaging>pom</packaging>     <version>1.0-SNAPSHOT</version>     <modules>         <module>Main</module>         <module>Dep</module>     </modules> </project> 

And two child projects:

<?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">     <parent>         <artifactId>Test</artifactId>         <groupId>org.example</groupId>         <version>1.0-SNAPSHOT</version>     </parent>     <modelVersion>4.0.0</modelVersion>      <artifactId>Main</artifactId>      <dependencies>         <dependency>             <groupId>org.example</groupId>             <artifactId>Dep</artifactId>             <version>1.0-SNAPSHOT</version>         </dependency>     </dependencies> </project> 

and:

<?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">     <parent>         <artifactId>Test</artifactId>         <groupId>org.example</groupId>         <version>1.0-SNAPSHOT</version>     </parent>     <modelVersion>4.0.0</modelVersion>      <artifactId>Dep</artifactId> </project> 

Main module has Main class with main method(lol)

public class Main {     public static void main(String[] args) {         Hello hello = new Hello();         System.out.println(hello.sayHello());     } } 

Class Hello is defined in the Dep module. What should I add into my poms to build executable jar with Main class from Main module as entry point?

Answer 1

You need to change your pom for artifactid Main. You need to add the maven-assembly-plugin

In the configuration of it you have an option to specify the mainClass in the manifest. This should be the fully qualified name of the Main class.

<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>     <parent>         <groupId>org.example</groupId>         <artifactId>Test</artifactId>         <version>1.0-SNAPSHOT</version>     </parent>     <artifactId>Main</artifactId>      <properties>         <!-- plugins -->         <maven.assembly.plugin.version>2.4</maven.assembly.plugin.version>         <!-- dependencies -->         <dep.version>1.0-SNAPSHOT</dep.version>     </properties>      <build>         <plugins>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-jar-plugin</artifactId>             </plugin>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-assembly-plugin</artifactId>             </plugin>         </plugins>          <pluginManagement>             <plugins>                 <plugin>                     <groupId>org.apache.maven.plugins</groupId>                     <artifactId>maven-assembly-plugin</artifactId>                     <version>${maven.assembly.plugin.version}</version>                     <configuration>                         <descriptorRefs>                             <descriptorRef>jar-with-dependencies</descriptorRef>                         </descriptorRefs>                         <archive>                             <manifest>                                 <mainClass>Main</mainClass>                             </manifest>                         </archive>                     </configuration>                     <executions>                         <execution>                             <id>make-assembly</id>                             <phase>package</phase>                             <goals>                                 <goal>single</goal>                             </goals>                         </execution>                     </executions>                 </plugin>             </plugins>         </pluginManagement>     </build>      <dependencies>         <dependency>             <groupId>org.example</groupId>             <artifactId>Dep</artifactId>             <version>${dep.version}</version>         </dependency>     </dependencies> </project> 

After you start your build on the parent project, it should create the executable jar in the target subfolder of the module Main. (a jar with the name Main-1.0-SNAPSHOT-jar-with-dependencies.jar was what i got)