Executable jar won't find the properties files

Properties properties = new Properties();
URL url = new App().getClass().getResource(PROPERTIES_FILE);
properties.load(url.openStream());

<plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>2.2</version>
    <configuration>
      <descriptorRefs>
        <descriptorRef>jar-with-dependencies</descriptorRef>
      </descriptorRefs>
      <archive>
        <manifest>
          <mainClass>com.stackoverflow.App</mainClass>
        </manifest>
        <manifestEntries>
          <Class-Path>.</Class-Path> <!-- HERE IS THE IMPORTANT BIT -->
        </manifestEntries>
      </archive>
    </configuration>
    <executions>
      <execution>
        <id>make-assembly</id> <!-- this is used for inheritance merges -->
        <phase>package</phase> <!-- append to the packaging phase. -->
        <goals>
          <goal>single</goal> <!-- goals == mojos -->
        </goals>
      </execution>
    </executions>
  </plugin>

java -cp .;filename.jar com.example.YourClassWithMain

URL root = getClass().getProtectionDomain().getCodeSource().getLocation();
URL propertiesFile = new URL(root, "filename.properties");
Properties properties = new Properties();
properties.load(propertiesFile.openStream());

Class-Path: .

<plugin>
        <artifactId>maven-jar-plugin</artifactId>
        <configuration>
                <resources>
                        <resource>
                                <directory>src/main/java</directory>
                                <includes>
                                        <include>**/*properties</include>
                                </includes>
                        </resource>
                </resources>
        </configuration>
<plugin>

<!-- Create a custom MANIFEST.MF file, setting the classpath. -->
<delete file="${project.base.dir}/resources/MANIFEST.MF" failonerror="false"/>
<manifest file="${project.base.dir}/resources/MANIFEST.MF">
  <attribute name="Class-Path" value="." />
</manifest>

<!-- JAR the server-side code, using the custom manifest from above. -->
<jar destfile="services/${name}.aar" manifest="${project.base.dir}/resources/MANIFEST.MF">
[....]