How to register a custom built jar file as maven main artifact?

Question

I have a project expected to deliver a jar file:

<packaging>jar</packaging>

but the jar is built in a custom way, so the default packaging done with jar:jar has been disabled

<plugin>
  <artifactId>maven-jar-plugin</artifactId>
  <version>2.3.2</version>
  <executions>
    <execution>
      <id>default-jar</id>
      <phase>none</phase>
    </execution>
  </executions>
</plugin>

but then when I want to apply shade:shade on the existing jar I get an error

The project main artifact does not exist.

I assume that maven doesn't know about the .jar file created by my custom tool. How to let it know, because antrun attachArtifact doesn't work

<attachartifact file="./bin/classes.jar" classifier="" type="jar"/>

the error I get is

An Ant BuildException has occured: org.apache.maven.artifact.InvalidArtifactRTException: For artifact {:jar}: An attached artifact must have a different ID than its corresponding main artifact.

So this is not the method to register main artifact... Is there any (without writing custom java plugin)?

Thanks, Lukasz

score 2 · Accepted Answer · answered Jul 20 '15 at 10:04

I checked the sources of JarMojo and it gave me an idea how to solve it with Groovy (via gmaven)

<plugin>
  <groupId>org.codehaus.gmaven</groupId>
  <artifactId>gmaven-plugin</artifactId>
  <version>1.3</version>
  <executions>
    <execution>
      <id>set-main-artifact</id>
      <phase>package</phase>
      <goals> 
        <goal>execute</goal>
      </goals>
      <configuration>
        <source>
          project.artifact.setFile(new File("./bin/classes.jar"))
        </source>
      </configuration>
    </execution>
  </executions>
</plugin>

and it works!:)

score 1 · Answer 2 · edited Jun 15 '22 at 14:34

We were having the same problem, with getting the "attached artifact must have a different ID than its corresponding main artifact" error. We found the solution in the following excellent blog post:

embed-and-run-ant-tasks-and-scripts-from-maven

As detailed in this section, you can fix the problem by adding a classifier so Maven can distinguish between the ant-built jar and the maven-built jar. Since you're using antrun attachartifact, you'd need this:

<attachartifact file="./bin/classes.jar" classifier="foo" type="jar"/>

Note you'll also need to include that classifier (along with groupId, artifactId and version) whenever you want to grab this jar as a dependency in other projects.

score 1 · Answer 3 · answered Apr 24 '13 at 19:40

Something like this

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <version>1.8</version>
    <executions>
        <execution>
            <id>attach-artifacts</id>
            <phase>package</phase>
            <goals>
                <goal>attach-artifact</goal>
            </goals>
            <configuration>
                <artifacts>
                    <artifact>
                        <file>${basedir}/bin/classes.jar</file>
                        <type>jar</type>
                    </artifact>
                </artifacts>
            </configuration>
        </execution>
    </executions>
</plugin>

This won't work -- you will have the same error as in the question: An attached artifact must have a different ID than its corresponding main artifact. — Oleg Efimov, Dec 07 '18 at 09:37

score 1 · Answer 4 · answered Aug 19 '14 at 21:55

While your solution may work for a build to the install+ phase or where there are no dependencies in the reactor, in cases where only building to the compile or test phase the unpackaged classes won't be found by dependencies. Building to compile happens when using plugins like the maven-release-plugin.

Extending your chosen solution to include identifying the unpacked classes during compile

<plugin>
  <groupId>org.codehaus.gmaven</groupId>
  <artifactId>gmaven-plugin</artifactId>
  <version>1.3</version>
  <executions>
    <execution>
      <id>set-main-artifact-compile</id>
      <phase>compile</phase>
      <goals> 
        <goal>execute</goal>
      </goals>
      <configuration>
        <source>
          project.artifact.setFile(new File("./bin/classes"))
        </source>
      </configuration>
    </execution>
    <execution>
      <id>set-main-artifact</id>
      <phase>package</phase>
      <goals> 
        <goal>execute</goal>
      </goals>
      <configuration>
        <source>
          project.artifact.setFile(new File("./bin/classes.jar"))
        </source>
      </configuration>
    </execution>
  </executions>
</plugin>

By default the maven-install-plugin will use the identified artifact along the lines of ${project.build.directory}/${project.finalname}.jar

So another option might go something like this

<build>
    <directory>bin</directory>
    <outputDirectory>bin/classes</outputDirectory>
    <finalName>classes</finalName>
</build>

in multi-module relative paths don't work. I set `${basedir}/../jars-bundle/xxx.jar` and use `project.properties["prebuilt.jar"]` in groovy — basin, Jul 24 '18 at 13:51

How to register a custom built jar file as maven main artifact?

4 Answers4

Linked