Maven has for me a non user friendly documentation, with 80% of xml content. For long time I have been stuck in how easily manage both dependency from maven central and from local jars.

I finally got something quite general and functional. Here is how to make this working fine:

The pom.xml file:

<!-- Add the manifest -->
<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-jar-plugin</artifactId>
  <version>2.4</version>
  <configuration>
    <archive>
      <manifest>
        <mainClass>your.class.Main</mainClass>
      </manifest>
    </archive>
  </configuration>
</plugin>

<!-- Make a standalone build -->
<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-shade-plugin</artifactId>
  <version>2.2</version>
  <executions>
    <execution>
      <phase>package</phase>
      <goals>
        <goal>shade</goal>
      </goals>
      <configuration>
        <outputFile>
        ${project.build.directory}/${artifactId}-${version}-standalone.jar
        </outputFile>
      </configuration>
    </execution>
  </executions>
</plugin>

<!--  import your local jar-->
<dependency>
  <groupId>org.hsqldb</groupId>
  <artifactId>jdbcDriver</artifactId>
  <version>2.4.1</version>
</dependency>

<!-- create a local respository  -->
<repositories>
  <repository>
    <id>my-local-repo</id>
    <url>file://${basedir}/repos</url>
  </repository>
</repositories>

By the way one can add dependency jars by such command line. This will populate the repos folder:

mvn org.apache.maven.plugins:maven-install-plugin:2.3.1:install-file
-Dfile=lib/hsqldb.jar
-DgroupId='org.hsqldb'
-DartifactId='jdbcDriver'
-DgeneratePom=true
-Dpackaging=jar
-Dversion=2.4.1
-DlocalRepositoryPath=repos

As a result, the compilation will result as a standalone jar, containing both local and central dependencies.