Maven assembly plugin

The Maven Assembly plugin is a plugin you can use to create arbitrary distributions for your applications. You can use the Maven Assembly plugin to assemble the output of your project in any format you desire by defining a custom assembly descriptor.
we’re going to use the predefined jar-with-dependencies format. To configure the Maven Assembly Plugin, we need to add the following plugin configuration to our existing build configuration in the pom.xml.

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

Once you’ve added this configuration, you can build the assembly by running the assembly:assembly goal. In the following screen listing, the assembly:assembly goal is executed after the Maven build reaches the install lifecycle phase:
 While it is certainly valid to execute a plugin goal directly from the command-line as we just demonstrated, it is more consistent with the design of Maven to configure the Assembly plugin to execute the assembly:assembly goal during a phase in the Maven lifecycle.

The following plugin configuration configures the Maven Assembly plugin to execute the attached goal during the package phase of the Maven default build lifecycle. The attached goal does the same thing as the assembly goal. To bind to assembly:attached goal to thepackage phase we use the executions element under plugin in the build section of the project’s POM.

<plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>simple-command</id>
                        <phase>package</phase>
                        <goals>
                            <goal>attached</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

Once you have this configuration in your POM, all you need to do to generate the assembly is run mvn package. The execution configuration will make sure that the assembly:attached goal is executed when the Maven lifecycle transitions to the package phase of the lifecycle. The assembly will also be created if you run mvn install as the package phase precedes the install phase in the default Maven lifecycle.