Maven dependency issue in eclipse

问题:

I have multiple related projects open in a workspace in eclipse. One of the projects has a maven dependency on the output jar from another project. In this project, any references to the classes in the dependency always show up as red (unidentified) and I get no code completion or javadoc showing up for them. If I manually add the jar to the classpath, then I no longer have this problem. The thing is, I don't want to have to manually add the jar every time our revision changes, that's what Maven is for. Any ideas on how I can resolve this? it seems like a bug to me, but I'm not sure...

回答1:

The correct way to do this is the following:

• Make sure that m2e or m2eclipse (depending on your version of Eclipse) is installed: http://www.eclipse.org/m2e/
• Use the dependencies section in the POM file exclusively, don't fiddle with the Eclipse project references. Right-click the project, then select Maven > Update Project Configuration to reset the project to the Maven default settings. This way, m2e has ownership of the dependencies.
• If you don't have that option, you might need to enable the project for Maven usage. Right-click the project, then Maven > Enable Workspace Resolution or Maven > Enable Dependency Management.
• Make sure all referenced projects are open in Eclipse and have the Maven nature enabled.
• Check the Maven settings for each project, make sure that groupId, artifactId and version match with the projects you have open in Eclipse. So if the project you depend on has version 1.0.0-SNAPSHOT in Eclipse, make sure that the depending project's POM file references version 1.0.0-SNAPSHOT in the dependencies section.
• Enable Workspace Resolution for each of the projects. Right-click the project, then Maven > Enable Workspace Resolution.
• Finally, if the projects are still not resolved, right-click the project again, then Maven > Update Dependencies

This should solve your problem.

回答2:

I had the same issue and resolved the problem by right-clicking on the project and selecting Maven -> Disable Workspace Resolution from the context menu. I had already tried updating the project from the POM file as described above.

回答3:

In order to fix this typically you can copy the Eclipse .classpath file from a working project since there isn’t anything project specific here assuming you’re structured as a standard Maven project. This will tell Eclipse to allow Maven to manage the dependencies and build. There seems to be no easy way to do this from the Eclipse UI.