How to create a .jar out of multiple jars using Maven Plugin

Question

I have a project which has multiple .jar files in it. To add this as a dependency, I need to turn all these jars into one big jar. So far I have come until:

    <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>mainProjects</groupId>
      <artifactId>mainProjects.master</artifactId>
      <relativePath>../pom.xml</relativePath>
      <version>1.0.0-SNAPSHOT</version>
   </parent>
   <groupId>mainProjects</groupId>
   <artifactId>sampleModule1</artifactId>
   <name>sampleModule1</name>
   <version>1.0.0.qualifier</version>
   <build>
    <plugins>
     <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <executions>
            <execution>
                <phase>package</phase>
                <goals>
                    <goal>shade</goal>
                </goals>
                <configuration>
                    <artifactSet>
                    <includes>
                        <include>Sample1.jar</include>
                        <include>Sample2.jar</include>
                     </includes>
                    </artifactSet>
                    <finalName>${project.artifactId}-${project.version}-final</finalName>
                    <outputDirectory>${project.artifactId}/build</outputDirectory>
                    <shadedArtifactAttached>false</shadedArtifactAttached>
                </configuration>
            </execution>
        </executions>
    </plugin>
    </plugins>
</build>
</project>

This creates the final jar, however, inside there are no content from the other jars (sample1.jar and sample2.jar) as there should be. I have looked into the documentation of the plugin, however all they did was to do it via class files, not jars. So I don't know how to proceed from now on.

Any thoughts?

Update:

So in order to make it clear, hereby I share the project structure that I have:

 +- mainProjects
 |   +- pom.xml
 |   +- mainProject1
 |   |  +- pom.xml
 |   |  +- src
 |   +- mainProject2 
 |   |  +- pom.xml
 |   |  +- src   
 |   +- group1
 |   |  +- pom.xml  
 |   |  +- sampleModule1
 |   |  | +- pom.xml  
 |   |  | +- build
 |   |  | +- sample1.jar
 |   |  | +- sample2.jar
 |   |  | +- sample3.jar
 |   |  | +- sample4.jar
 |   |  | +- sample5.jar
 |   |  | +- sample6.jar
 |   |  +- sampleModule2
 |   |  | +- pom.xml
 |   |  | +- src

Now, I want to be able to use sampleModule1 as a dependency in the pom.xml of mainProject1 as a jar, like this:

      <dependency>
         <groupId>group1</groupId>
         <artifactId>sampleModule1</artifactId>
         <version>1.0.0.qualifier</version>
         <scope>system</scope>
         <systemPath>sampleModule1/build/${project.artifactId}-${project.version}-final.jar</systemPath>
   </dependency>

to achieve this, I need to compile all the jars into one jar, so that I can add it by using one systemPath. I found this which shows an example of how to include multiple files into one. However, in the example they are not jars, but rather classes and others. Now here, I am trying to achieve the same, but with only jars.

Answer 1

There are two ways to solve your problem! If you just want to to add files into your jar, you can use the resources tags to add them

<build>
    <resources>
        <resource>
            <filtering>false</filtering>
            <directory>lib</directory>
            <includes>
                <include>*.jar</include>
            </includes>
        </resource>
    </resources>
</build>

This now puts all jar files from you lib folder into the main jar. The root folder is the folder from which you invoked the corresponding pom.xml. With this you can add arbitrary files to you jar. For a complete syntax reference take a look here.

The other way and maybe the most convenient way is to use the maven-shade-plugin this allows you to copy almost everything into you final jar.

<?xml version="1.0" encoding="UTF-8"?>
<plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-shade-plugin</artifactId>
   <version>2.4.3</version>
   <executions>
      <execution>
         <phase>package</phase>
         <goals>
            <goal>shade</goal>
         </goals>
         <configuration>
            <artifactSet>
               <includes>
                  <include>groupid:artifactid_a</include>
                  <include>groupid:artifactid_b</include>
               </includes>
            </artifactSet>
            <filters>
               <filter>
                  <artifact>*:*</artifact>
                  <includes>
                     <include>resources/*.png</include>
                  </includes>
               </filter>
            </filters>
         </configuration>
      </execution>
   </executions>
</plugin>

The artifactSet parts allow you to reference jar from within you local repro to be included just by mentioning their groupid and artifactid

This will include the content like class files, manifest etc. and also the folder structure) of the mentioned artifact (from you local repro) into you jar.

If you want to include other arbitrary files into you jar you can use the filter tag of the plugin which allows you to specify files and file-patterns directly. For a complete syntax reference take a look here.

P.S.: If you want to exclude certain files you can replace the include tag by an exclude tag ;-)