Maven suddenly wants src/ instead of src/main/java

Question

I'm using Maven 3.3.3 together with Eclipse Mars and m2e. Yesterday, I created a new Java project and converted it into a Maven one.

Afterwards, the classpath contained only src instead of the standard src/main/java. I was surprised but I simply created the missing folders and ran m2e's "Update Project". This didn't solve the problem; m2e still insisted on using only src.

So I edited the classpath manually to end up with with the usual

src/test/java
src/test/resources
src/main/java
src/main/resources

When I try m2e's "Update Project" now, I get this error:

Cannot nest 'foo/src/test/java' inside 'foo/src'. To enable the nesting, exclude 'test/' from 'foo/src'

sigh I went to the command line next and ran mvn eclipse:eclipse to get this classpath:

src/test/java
src/test/resources
src
src/main/resources

Now, I'm completely stumped. Why is that happening?

Answer 1

Open your POM in the POM editor and click on the "Effective POM" tab. Search for sourceDirectory. You'll probably see something like this:

<sourceDirectory>src</sourceDirectory>

When you first converted the Java project to Maven, m2e tried to keep the classpath the same. Eclipse Java projects have a different layout by default. They use src/ instead of src/main/java/. There is no test folder since Eclipse projects usually put their tests into a different project.

To fix the issue:

1. Delete the sourceDirectory element from the POM (Note: It might be in a parent POM).
2. Go to the project
3. Select all the source folders
4. Remove them from the build path (context menu -> Build Path -> Remove From Build Path).
5. Update the project

The error should now be gone and the classpath should be correct.