Friday, July 18, 2014

Solving Eclipse and Maven problems:

"Failed to read artifact descriptor for"

I've spent most of today trying to add a dependency for the Cassandra Java driver to a maven pom in eclipse with little luck at all.  Worst when I tried it on another machine it worked fine so it was something wrong with my mac laptop.  Nothign I did would work, I kept on getting a error " Failed to read artifact descriptor for com.datastax.cassandra" etc. Looking at:

Stackoverflow: Maven: Failed to read artifact descriptor 

It suggested Maven -> Update Project and click on the force option.  No joy there !  It was only when I tried a manual mvn -U clean install command that I got the full error:
 "Failed to execute goal on project testmaven: Could not resolve dependencies for project Failed to collect dependencies at com.datastax.cassandra:cassandra-driver-core:jar:2.0.3: Failed to read artifact descriptor for com.datastax.cassandra:cassandra-driver-core:jar:2.0.3: Could not transfer artifact com.datastax.cassandra:cassandra-driver-core:pom:2.0.3 from/to central ( Specified destination directory cannot be created: /Users/Administrator/.m2/repository/com/datastax/cassandra/cassandra-driver-core/2.0.3"
Looking at the permissions on /Users/Administrator/.m2/repository/com/datastax/cassandra/ did I see that the sub directories where owned by root. I must have used sudo at some point to manually build the cassandra java driver from a git repo (in fact I knew I did).

The answer then was to delete  /Administrator/.m2/repository/com/datastax and then run the force maven project update in eclipse.

All now works well !

Update to Java 1.8

I also ran into a problem changing the java version of a project from 1.5 to 1.7 or 1.8.  Yes you can change the project facet, but you'll find that a maven update will change it back to 1.5.  This stakoverflow has the correct answer:

Java. Warning - Build path specifies execution environment J2SE-1.4

Open the pom.xml file and add the following to the section

You will need to do a maven update from eclipse after that.

Change Web app facet to 3.0

If you create a dynamic webapp from the file->new->maven project and select maven-archetype-webapp you may find that it is "stuck" at version 2.3.  If you try and change it to 2.4 or higher (3.1 for instance) you'll be prevented. Deep inside this thread is on stackoverflow is the correct answer (for me):

Cannot change version of project facet Dynamic Web Module to 3.0?

In eclipse, go to window->show vie -> navigator.  Now in the navigator window you should see the .settings folder.  Open the folder and open the file org.eclipse.wst.common.project.facet.core.xml  Inside that file you should see jst.web and you can change the webapp facet version there.  Again do a maven update from eclipse after that.