Why Maven Assembly Plugin does not include my project files in the jar with dependencies ?

Question

I am using maven assembly plug in to package my project with all its dependency so i can run a simple java -jar myproject.jar and be able to run the project. However when I ran the jar it told me

Error: Could not find or load main class com.project.ServerStart

Then I unzipped the .jar file and found that the assembly does not include my project files, which is ridiculous !
When packaging the project I receive this warning

[WARNING] Cannot include project artifact: Amjar:amjar:pom:0.2; it doesn't have an associated file or directory.

This is my plugin config

<build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>2.4</version>
        <configuration>
          <finalName>amjar-${project.version}</finalName>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
          <archive>
            <manifest>
              <addClasspath>true</addClasspath>
              <mainClass>com.project.ServerStart</mainClass>
            </manifest>
          </archive>
        </configuration>
        <executions>
          <execution>
            <id>assemble-all</id>
            <phase>package</phase>
            <goals>
              <goal>single</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

What am I doing wrong ?

Answer 1

From the warning you've included in your question:

[WARNING] Cannot include project artifact: Amjar:amjar:pom:0.2; it doesn't have an associated 

I'd guess that you've got the packaging in your pom.xml set to pom.

This is fine if your module is simply packaging a set of dependencies or resource files, however, if you also want Maven to create a jar containing the classes in you module you will need to set the packaging to jar.