Maven: Packaging dependencies alongside project JAR?

I've like Maven to package a project with run-time dependencies.

This part is unclear (it's not exactly what you describe just after). My answer covers what you described.

I expect it to create a JAR file with the following manifest (...)

Configure the Maven Jar Plugin to do so (or more precisely, the Maven Archiver):

<project>
  ...
  <build>
    <plugins>
      <plugin>
         <artifactId>maven-jar-plugin</artifactId>
         <configuration>
           <archive>
             <manifest>
               <addClasspath>true</addClasspath>
               <classpathPrefix>lib/</classpathPrefix>
               <mainClass>com.acme.MainClass</mainClass>
             </manifest>
           </archive>
         </configuration>
      </plugin>
    </plugins>
  </build>
  ...
  <dependencies>
    <dependency>
      <groupId>dependency1</groupId>
      <artifactId>dependency1</artifactId>
      <version>X.Y</version>
    </dependency>
    <dependency>
      <groupId>dependency2</groupId>
      <artifactId>dependency2</artifactId>
      <version>W.Z</version>
    </dependency>
  </dependencies>
  ...
</project>

And this will produce a MANIFEST.MF with the following entries:

...
Main-Class: fully.qualified.MainClass
Class-Path: lib/dependency1-X.Y.jar lib/dependency2-W.Z.jar
...

and create the following directory structure (...)

This is doable using the Maven Dependency Plugin and the dependency:copy-dependencies goal. From the documentation:

dependency:copy-dependencies takes the list of project direct dependencies and optionally transitive dependencies and copies them to a specified location, stripping the version if desired. This goal can also be run from the command line.

You could bind it on the package phase:

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>2.1</version>
        <executions>
          <execution>
            <id>copy-dependencies</id>
            <phase>package</phase>
            <goals>
              <goal>copy-dependencies</goal>
            </goals>
            <configuration>
              <outputDirectory>${project.build.directory}/lib</outputDirectory>
              <overWriteReleases>false</overWriteReleases>
              <overWriteSnapshots>false</overWriteSnapshots>
              <overWriteIfNewer>true</overWriteIfNewer>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  [...]
</project>

Add the following plugins in pom.xml. Check the value at mainClass,classpathPrefix,addClasspath tags.

<plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>2.4</version>
        <configuration>
            <archive>
                <manifest>
                    <mainClass>org.apache.camel.spring.Main</mainClass>
                    <classpathPrefix>lib/</classpathPrefix>
                    <addClasspath>true</addClasspath>
                </manifest>
            </archive>
        </configuration>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>2.4</version>
        <configuration>
            <descriptors>
                <descriptor>src/assembly/some-assembly.xml</descriptor>
            </descriptors>
        </configuration>
        <executions>
            <execution>
                <id>make-assembly</id>
                <phase>package</phase>
                <goals>
                    <goal>single</goal>
                </goals>
            </execution>
        </executions>
    </plugin>

Create some-assembly.xml under src/assembly as below.

<assembly
xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
<id>distribution</id>
<formats>
    <format>zip</format>
</formats>
<includeBaseDirectory>true</includeBaseDirectory>
<fileSets>
    <fileSet>
        <directory>${project.build.directory}</directory>
        <outputDirectory>/</outputDirectory>
        <includes>
            <include>*.jar</include>
        </includes>
    </fileSet>
</fileSets>
<dependencySets>
    <dependencySet>
        <scope>runtime</scope>
        <outputDirectory>/lib</outputDirectory>
        <useProjectArtifact>false</useProjectArtifact>
        <unpack>false</unpack>
    </dependencySet>
</dependencySets>

Note that useProjectArtifact flag to false, unpack flag to false. If root folder inside zip file is not required,then one can make includeBaseDirectory to false.

This will create name-version-distribution.zip file. Inside zip file, there will be folder name-version. Inside this folder, your executable jar and lib folder containing all dependency jars will be present. Check manifest.MF file of executable jar. It contains both main class and classpath information.

Maven: Packaging dependencies alongside project JAR?

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