How to create a non-executable JAR file that includes all Maven dependencies

I have a Java project that doesn’t have a main file but it has a lot of Maven dependencies.

How I can create a JAR-file that contains my source-code and required maven dependencies?

My 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>NetworkCommunicationAPI</groupId>
    <artifactId>NetworkCommunicationAPI</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <build>
        <sourceDirectory>src</sourceDirectory>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <dependency>
      <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20210307</version>
        </dependency>
    </dependencies>
</project>

Answer

You can use the maven-assembly-plugin just as you could use it for creating an executable JAR with dependencies.

The only thing you need to change is that you don’t need to specify a main class:

<build>
  <plugins>
    <plugin>
      <artifactId>maven-assembly-plugin</artifactId>
      <configuration>
        <descriptorRefs>
          <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
      </configuration>
    </plugin>
  </plugins>
</build>

After that, you can create the JAR using mvn compile assembly:single.

This compiles your sources and creates a JAR containing the compiled sources and all dependencies in the compile-scope.