Basic maven plugin project not working, Mojo plugin descriptors not generating

Question

I am following the tutorial for creating a maven plugin and cannot run mvn install without getting errors. The info complains that i don't have the required mojo descriptors when the annotations should be generating them for me. I am running maven 3.0.5 and using intellij as my ide. here is my Main class:

@Mojo(name = "modify-connector")
public class ComplianceMojo extends AbstractMojo {

    @Parameter
    private String artifactId;

    @Parameter
    private String version;

    @Override
    public void execute() throws MojoExecutionException, MojoFailureException {
        File jar = new File(getPluginContext().get("project.build.directory") + "/"
                + getPluginContext().get("project.build.finalname") + "/" + artifactId + "-" + version);
        if(jar.exists()){
            getLog().info("The file exists! " + jar.getAbsolutePath());
        } else {
            getLog().info("The file does not exist: " + jar.getAbsolutePath());
        }
    }
}

And here is my pom.xml

<?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>

    <groupId>mysql-jdbc-compliance-maven-plugin</groupId>
    <artifactId>mysql-jdbc-compliance-maven-plugin</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>maven-plugin</packaging>

    <dependencies>
        <dependency>
            <groupId>org.apache.maven</groupId>
            <artifactId>maven-plugin-api</artifactId>
            <version>2.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.plugin-tools</groupId>
            <artifactId>maven-plugin-annotations</artifactId>
            <version>3.2</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

</project>

Note: I had to separately add the annotations dependency as the main plugin api did not contain these classes. when i run mvn install on my project, the output is as follows:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.867s
[INFO] Finished at: Wed Sep 25 17:45:55 EST 2013
[INFO] Final Memory: 8M/244M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:2.9:descriptor (default-descriptor) on project mysql-jdbc-compliance-maven-plugin: Error extracting plugin descriptor: 'No mojo definitions were found for plugin: mysql-jdbc-compliance-maven-plugin:mysql-jdbc-compliance-maven-plugin.' -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

score 65 · Answer 1 · edited Feb 13 '19 at 21:26

65

Maybe this is related to a unresolved issue in Maven: https://issues.apache.org/jira/browse/MNG-5346

For my plugin projects, i could workaround by adding an explicit execution of the maven-plugin-plugin:

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-plugin-plugin</artifactId>
                <version>3.2</version>
                <configuration>
                    <!-- see http://jira.codehaus.org/browse/MNG-5346 -->
                    <skipErrorNoDescriptorsFound>true</skipErrorNoDescriptorsFound>
                </configuration>

                <executions>
                    <execution>
                        <id>mojo-descriptor</id>
                        <goals>
                            <goal>descriptor</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

But see the comments in the JIRA issue for more elaborate solutions!

edited Feb 13 '19 at 21:26

turbanoff

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answered Sep 25 '13 at 08:15

Gyro Gearless

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I have read the issue you have posted and have implemented the work around on the website and it has worked! Thanks for pointing it out to me :) – coderatchet Sep 25 '13 at 08:30
9

This issue has been fixed in 3.2.2: http://maven.apache.org/docs/3.2.2/release-notes.html – Chris Parton Sep 05 '14 at 02:57
Thank you, this solved my build issue on a machine running Maven 3.0.5 – qqilihq Nov 29 '15 at 10:31
2

Half a decade later and this solution still holds when maven-plugin-plugin crashes on maven 3.6.3. Thank you – GideonleGrange Sep 24 '20 at 10:22
I can still reproduce the issue in 3.5+, but luckily this same solution still works to fix it! Thanks! – Matsu Q. Oct 19 '20 at 16:55
This works around the problem but I've found that deployed plugins do not work because the `plugins-help.xml` file is not properly generated. – Gray Jan 27 '21 at 00:58

score 41 · Accepted Answer · edited Mar 20 '18 at 16:06

after reading the Jira Issue that Gyro posted, i added the following lines to my pom and everything compiled nicely.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-plugin-plugin</artifactId>
            <version>3.2</version>
            <configuration>
                <goalPrefix>mysql-jdbc-compliance</goalPrefix>
            </configuration>
            <executions>
                <execution>
                    <id>default-descriptor</id>
                    <goals>
                        <goal>descriptor</goal>
                    </goals>
                    <phase>process-classes</phase>
                </execution>
                <execution>
                    <id>help-descriptor</id>
                    <goals>
                        <goal>helpmojo</goal>
                    </goals>
                    <phase>process-classes</phase>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

This entry is actually added to your plugin's `pom.xml` automatically if you generate the project using maven archetype: `mvn archetype:generate -DgroupId=com.example -DartifactId=my-awesome-maven-plugin -DarchetypeGroupId=org.apache.maven.archetypes -DarchetypeArtifactId=maven-archetype-plugin` — Jan Molak, Jul 09 '15 at 11:39
With mvn 3.3.9 I only required groupId, artifactId and v3.5 - all the config is default. — Adam, Nov 02 '17 at 09:53

score 38 · Answer 3 · edited Jan 19 '22 at 05:21

38

As mentioned in the previous answer, this was a bug and it is now fixed.

You just need to tell maven it should use a newer version of the maven-plugin-plugin.

Here is what my pom file looks like:

<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">
  <!-- ...other maven config... -->
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-plugin-plugin</artifactId>
        <version>3.3</version>
      </plugin>
    </plugins>
  </build>
</project>

edited Jan 19 '22 at 05:21

Dave Moten

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answered Jun 25 '15 at 06:39

Jmini

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1

Version 3.6.1 as of 2019-06-10 – jordiburgos Jun 10 '19 at 16:17
1

@jordiburgos https://search.maven.org specifies 3.6.0 for the latest version as of 2019-07-16 (which was updated on 2018-10-29) – ᴠɪɴᴄᴇɴᴛ Jul 16 '19 at 16:03
https://search.maven.org/artifact/org.apache.maven.plugins/maven-plugin-plugin for latest version – rohanagarwal Mar 01 '22 at 10:54

score 16 · Answer 4 · edited Jan 27 '21 at 16:08

Simply incrementing maven plugin version to 3.3 or 3.4 won't fix any issue (as some has stated).

You have to add a minimum of default-descriptor execution with the correct phase. So the minimum config of build information is as follows:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-plugin-plugin</artifactId>
            <version>3.1</version>
            <executions>
                <execution>
                    <id>default-descriptor</id>
                    <phase>process-classes</phase>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

irrespective of maven-plugin-plugin version. (it can be 3.1, 3.2, 3.3. 3.4 (didn't test the others)).

will yield:

...
[INFO] --- maven-plugin-plugin:3.2:descriptor (default-descriptor) @ example-maven-plugin ---
[WARNING] Using platform encoding (UTF-8 actually) to read mojo metadata, i.e. build is platform dependent!
[INFO] Applying mojo extractor for language: java-annotations
[INFO] Mojo extractor for language: java-annotations found 1 mojo descriptors.
[INFO] Applying mojo extractor for language: java
[INFO] Mojo extractor for language: java found 0 mojo descriptors.
[INFO] Applying mojo extractor for language: bsh
[INFO] Mojo extractor for language: bsh found 0 mojo descriptors.
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

Another option if you don't want to have build tags in your pom, you can use javadocs on your Mojo. For instance:

/**
 * @goal run123
 */
@Mojo(name = "run123")
public class MyMojo extends AbstractMojo {
}

will yield:

...
[INFO] --- maven-plugin-plugin:3.2:descriptor (default-descriptor) @ example-maven-plugin ---
[WARNING] Using platform encoding (UTF-8 actually) to read mojo metadata, i.e. build is platform dependent!
[INFO] Applying mojo extractor for language: java-annotations
[INFO] Mojo extractor for language: java-annotations found 0 mojo descriptors.
[INFO] Applying mojo extractor for language: java
[INFO] Mojo extractor for language: java found 1 mojo descriptors.
[INFO] Applying mojo extractor for language: bsh
[INFO] Mojo extractor for language: bsh found 0 mojo descriptors. 
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

Please refer to this guide for more info http://maven.apache.org/plugin-tools/maven-plugin-plugin/examples/using-annotations.html

Adding the descriptor should occur automatically when you build your plugin. Also, you don't need to declare the maven-plugin-plugin dependency as this is also automatically found when building a project with packaging `maven-plugin` declared. However you might not get the latest version - with mvn 3.3.9 I was getting maven-plugin-plugin 3.2, so I had to declare the dependency to specify v3.5 — Adam, Nov 02 '17 at 09:51
++ This is the only answer that worked for me. It looks like that the plugin runs at a different phase by default which causes it to not find any mojo entries. — Gray, Jan 27 '21 at 01:05

score 5 · Answer 5 · answered Apr 02 '19 at 19:52

5

Great answers above -- I'd like to augment them by adding a resource to find the latest version: https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-plugin-plugin

April 2, 2019 -- I encountered the same error above and resolved it by using 3.6.0

answered Apr 02 '19 at 19:52

solbs

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It worked with target is 11 – duyetpt Nov 04 '21 at 10:40

Shane Gannon · Answer 6 · 2017-07-10T13:25:33.703

Initially I thought Gyro's answer fixed the error. But later when executing the goal it failed.

mvn sample.plugin:hello-maven-plugin:1.0-SNAPSHOT:sayhi

produced

[ERROR] Could not find goal 'sayhi' in plugin sample.plugin:hello-maven-plugin:1.0-SNAPSHOT among available goals -> [Help 1]

Turns out that

skipErrorNoDescriptorsFound

only suppressed the error. i.e. It did not resolve the underlying problem. I removed this fix.

After that the solution was simple (and the cause purely my fault). When I created GreetingMojo.java I placed it in the following directory

.../Development/my-maven-plugin/src/sample/plugin/GreetingMojo.java

It needed to be under

.../Development/my-maven-plugin/src/main/Java/sample/plugin/GreetingMojo.java

Thanks, that led me to my mistake. Adding src in the build section would include this source folders. — Jan Uhlig, May 14 '20 at 10:23

Basic maven plugin project not working, Mojo plugin descriptors not generating

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