Nexus repository contains artifact but only makes POM available - maven-2

Question

I have a Nexus instance with Maven 2 repositories hosted on a non-Internet-connected corporate development domain. I need to use the maven-jaxb-schemagen plugin from Sun, however, it was only available in Maven 1 format (along with many other Maven 1 dependencies, so this is not a one-off edge case).
I made a new Maven 1 hosted repository in Nexus (maven1), then made a Maven1-to-Maven2 virtual repository as well (maven1as2). Because some of the needed artifacts are snapshots, the policy for maven1 (and by extension maven1as2) is Snapshot.
I imported all of the Maven 1 artifacts through the filesystem to this repository's overridden local storage location.
I then added maven1as2 to my Public Repositories group. Some of the reference I have found says that Nexus will not allow you to browse or search a Maven1 repository. I have had mixed results. If I select Public Repositories or maven1as2 in Nexus, I can go to Browse Storage and drill down to com/sun/tools/jxc/maven2/maven-jaxb-schemagen-plugin/1.3-SNAPSHOT/ and view the maven-jaxb-schemagen-plugin-1.3-SNAPSHOT.pom file and its checksum. However, I cannot view the JAR artifact that should be there and is on the filesystem.
When I try to use Maven to build, I get the following:
$ mvn clean compile
[INFO] Scanning for projects...
[INFO] Reactor build order:
[INFO] MyProject
[INFO] MyModule1
[INFO] MyModule2
...
[INFO] ---------------------------------------------------------------------------
[INFO] Building MyProject
[INFO] task-segment: [clean, compile]
[INFO] ---------------------------------------------------------------------------
[INFO] [clean:clean {execution: default-clean}]
[INFO] [cobertura:clean {execution: default}]
[INFO] No goals needed for project - skipping
[INFO] ---------------------------------------------------------------------------
[INFO] Building MyModule1
[INFO] task-segment: [clean, compile]
[INFO] ---------------------------------------------------------------------------
Downloading: http://my.nexus.server:8081/nexus/content/groups/public/com/sun/tools/jxc/maven2/maven-jaxb-schemagen-plugin/1.3-SNAPSHOT/maven-jaxb-schemagen-plugin-1.3-SNAPSHOT.pom
6K downloaded (maven-jaxb-schemagen-plugin-1.3-SNAPSHOT.pom)
[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 download 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=com.sun.tools.jxc.maven2 -DartifactId=maven-jaxb-schemagen-plugin -Dversion=1.3-SNAPSHOT -Dpackaging=maven-plugin -Dfile=path/to/file
Alternatively, if you host your own repository you can deploy the file there:
mvn deploy:deploy-file -DgroupId=com.sun.tools.jxc.maven2 -DartifactId=maven-jaxb-schemagen-plugin -Dversion=1.3-SNAPSHOT -Dpackaging=maven-plugin -Dfile=path/to/file -Durl=[url] -DrepositoryId=[id]
com.sun.tools.jxc.maven2:maven-jaxb-schemagen-plugin:1.3-SNAPSHOT
from the specified remote repositories:
nexus (http://my.nexus.server:8081/nexus/content/groups/public)
com.sun.tools.jxc.maven2:maven-jaxb-schemagen-plugin:1.3-SNAPSHOT
from the specified remote repositories:
nexus (http://my.nexus.server:8081/nexus/content/groups/public)
[INFO] ---------------------------------------------------------------------------
[INFO] For more information, run Maven with the -e switch
[INFO] ---------------------------------------------------------------------------
[INFO] Total time: 2 seconds
[INFO] Finished at: Tue Jul 06 15:05:08 EDT 2010
[INFO] Final Memory: 7M/17M
[INFO] ---------------------------------------------------------------------------

Answer 1

Sometimes it happens when working with m2eclipse. You chose a dependency and the default scope is pom and not jar. You didn't show your pom file. validate that all dependencies are jar scoped.

Answer 2

I learned that most of the time rebuilding metadata of the repositories helps to solve such problems.
I find it annoying how often this is necessary.
Select the repository
In the "Browse Storage" tab open the context menu of the root node (it sometimes is hidden behind the Firefox default context menu - pressing Esc helps in this case and brings the Nexus context menu into view)
Select rebuild metadata
Expire cache and reindex may help too for some cases.
Most of the time these steps didn't solve the problem at the first try but at last they solved it each time though.
I run Nexus as a WAR in Glassfish 2.1