java - Maven is failing to download the tomcat-maven-plugin snapshot

Question

Even after wiping out my settings.xml, I still get this error when trying to use this snapshot dependency. Given the dependency:

<plugin>            
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>tomcat-maven-plugin</artifactId>
    <version>1.0-SNAPSHOT</version>
    <configuration>                 
        <path>/licensing</path>
        <tomcatWebXml>${basedir}/src/main/mock/web.xml</tomcatWebXml>
    </configuration>
</plugin>

And (in the POM), the plugin repository definition:

<pluginRepository>
    <id>Codehaus Snapshots</id>
    <url>http://snapshots.repository.codehaus.org</url>
    <snapshots>
        <enabled>true</enabled>
    </snapshots>
    <releases>
        <enabled>true</enabled>  <!-- Workaround for MNG-2974, see note below -->
    </releases>
</pluginRepository> 

I'm left with the following 404 error. If I actually navigate out to that repo, the jar it's looking for isn't there, just dated ones (I'm not familiar with the mechanics of how Maven ultimately resolves expected dependency names).

Ideas?

Downloading: http://snapshots.repository.codehaus.org/org/codehaus/mojo/tomcat-maven-plugin/1.0-SNAPSHOT/tomcat-maven-pl
ugin-1.0-SNAPSHOT.jar
[INFO] Unable to find resource 'org.codehaus.mojo:tomcat-maven-plugin:maven-plugin:1.0-SNAPSHOT' in repository Codehaus
Snapshots (http://snapshots.repository.codehaus.org)
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] A required plugin was not found: Plugin could not be found - check that the goal name is correct: Unable to downl
oad the artifact from any repository

Try downloading the file manually from the project website.

Then, install it using the command:
    mvn install:install-file -DgroupId=org.codehaus.mojo -DartifactId=tomcat-maven-plugin -Dversion=1.0-SNAPSHOT -Dpacka
ging=maven-plugin -Dfile=/path/to/file

Alternatively, if you host your own repository you can deploy the file there:
    mvn deploy:deploy-file -DgroupId=org.codehaus.mojo -DartifactId=tomcat-maven-plugin -Dversion=1.0-SNAPSHOT -Dpackagi
ng=maven-plugin -Dfile=/path/to/file -Durl=[url] -DrepositoryId=[id]


  org.codehaus.mojo:tomcat-maven-plugin:maven-plugin:1.0-SNAPSHOT

from the specified remote repositories:
  central (http://repo1.maven.org/maven2),
  Codehaus Snapshots (http://snapshots.repository.codehaus.org)


  org.codehaus.mojo:tomcat-maven-plugin:maven-plugin:1.0-SNAPSHOT

from the specified remote repositories:
  central (http://repo1.maven.org/maven2),
  Codehaus Snapshots (http://snapshots.repository.codehaus.org)


[INFO] ------------------------------------------------------------------------
[INFO] For more information, run Maven with the -e switch
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2 seconds
[INFO] Finished at: Wed Jan 06 10:06:49 EST 2010
[INFO] Final Memory: 14M/36M
[INFO] ------------------------------------------------------------------------

Answer 1

I rechecked and, with the following pom fragments:

<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/maven-v4_0_0.xsd">
  ...
  <pluginRepositories>
    <pluginRepository>
      <id>Codehaus Snapshots</id>
      <url>http://snapshots.repository.codehaus.org/</url>
      <snapshots>
        <enabled>true</enabled>
      </snapshots>
      <releases>
        <enabled>true</enabled>  <!-- Workaround for MNG-2974, see note below -->
      </releases>
    </pluginRepository>
  </pluginRepositories>
  ...
  <build>
    <finalName>my-webapp</finalName>
    <plugins>
      ...
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>tomcat-maven-plugin</artifactId>
        <version>1.0-SNAPSHOT</version>
      </plugin>
      ...
    </plugins>
   ...
  </build>
</project>

The SNAPSHOT of the plugin has been downloaded successfully:

$ mvn clean
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building my-webapp Maven Webapp
[INFO]    task-segment: [clean]
[INFO] ------------------------------------------------------------------------
[INFO] snapshot org.codehaus.mojo:tomcat-maven-plugin:1.0-SNAPSHOT: checking for updates from Codehaus Snapshots
[INFO] snapshot org.codehaus.mojo:tomcat-maven-plugin:1.0-SNAPSHOT: checking for updates from maven2-repository.dev.java.net
Downloading: http://snapshots.repository.codehaus.org//org/codehaus/mojo/tomcat-maven-plugin/1.0-SNAPSHOT/tomcat-maven-plugin-1.0-20091222.232027-11.pom
5K downloaded  (tomcat-maven-plugin-1.0-20091222.232027-11.pom)
Downloading: http://snapshots.repository.codehaus.org//org/codehaus/mojo/tomcat-maven-plugin/1.0-SNAPSHOT/tomcat-maven-plugin-1.0-20091222.232027-11.jar
48K downloaded  (tomcat-maven-plugin-1.0-20091222.232027-11.jar)
[INFO] [clean:clean {execution: default-clean}]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 9 seconds
[INFO] Finished at: Wed Jan 06 16:13:28 CET 2010
[INFO] Final Memory: 7M/78M
[INFO] ------------------------------------------------------------------------

It's very weird because I can't see any difference, but things are working as expected. In other words, I can't reproduce...

---

In your local repository, do you have maven-metadata*.xml files in the 1.0-SNAPSHOT directory for the tomcat-maven-plugin artifact? Do they match the ones on the remote server? Do they correctly specify the build number and timestamp?

If they are incorrect locally, running maven with -U might help.

You might also check mvn help:effective-pom and see what Maven thinks the updatePolicy is for snapshots on that repository.

Or maybe just delete your tomcat-maven-plugin artifact from your local repository and try again.

If nothing helps, try to install it manually (download the plugin from the repository and use the mvn install:install-file mojo) or checkout the sources from the VCS and build it locally. But these options are just workarounds, you have a problem somewhere (what version of maven are you using?).