I'm using Maven in Eclipse with the m2Eclipse plugin.
I'm very confused about how this is supposed to build within eclipse.
The on-the-fly compiling works as normal (i.e. as if without maven) so if you have an error it will be highlighted.
But when I want to run a junit for example, any changes to the code are only picked up after I run a maven build command. The Eclipse project clean doesn't seem to work.
Any help in explaining how this is all supposed to work would be greatly appreciated.
The eclipse builder uses simpler logic than maven, so sometimes the things m2eclipse does are just not enough. I usually keep a shell open to issue simple commands before I run unit tests. depending on your setup, here are some commands that might be helpful.
mvn process-resources
# This is usually enough when you have
# changed something in src/main/resources
If you know that the only resource processing needed is maven resource filtering, just call the goal:
mvn resources:resources
Same for tests:
mvn processs-test-resources
or
mvn resources:test-resources
If you need a fuller solution, because perhaps some new code has to be generated etc, then use
mvn test-compile
# This will through recursion process the following phases:
validate
initialize
generate-sources
process-sources
generate-resources
process-resources
compile
process-classes
generate-test-sources
process-test-sources
generate-test-resources
process-test-resources
test-compile
So you're getting pretty much everything except the actual unit test execution. Most plugins are smart enough to detect changes and leave unchanged files alone, so mvn test-compile is usually fast enough.
If you prefer not to use a shell, you can of course bind any of the above phases / goals to m2eclipse Run as... maven build targets.