Maven Integration for Eclipse

Actually it is trickier then it seems. You can't really use the same output folders between Eclipse compiler and any external tools, including Maven build. So, it is generally a bad idea to use the same output folders.

See discussion about this at https://bugs.eclipse.org/bugs/show_bug.cgi?id=99497

I understand what you want to say. Output folder may not be shared
by Eclipse and others. But what I'd like to say more is an inconvenient
behavior that 'Update Source Folders' action completely deletes
all custom output folder settings.

For instance, src/main/resources/log4j.properties and
src/test/resources/log4j.properties (for testing) are conflicted
by being copied into single output folder. So, I hope alternative function
to specify output folders for main resources and test resources respectively
on each subproject.

I am not sure how they can't conflict even when going under separate folders? They will end up in the same classpath anyways. Am I missing something?

Another thing is that action "Update Source Folders" intended to free you from worying about what source and target folders should be, as long as you have correct definitions in Maven's POM. we are open for suggestions how to improve it and keep it simple at the same time.

Sorry, I noticed that the example was wrong. What I meant was I didn't
want to gather resources of all subprojects into single output folder.

As you said, main resource and test resource will gather into the same classpath
at certain subproject, but I think that some resources of subproject-A
and independent subproject-B's one should not be gathered into
single classpath. How about this?

So I'd like to separate output folders per subproject, but currently
I have no idea for realize this.

Let's try to look at this from a different angle. why would you need these resources anyways? I can only think that they could be needed to run unit tests. However wWhen you run these tests from Maven resources already taken from the right folders. So, we may just add some support for JUnit runner within Eclipse that will use right resource folders when needed.

I tried to create a patch for this issue. This patch enables
to separate output folders per subprojects.

It adds a boolean property 'Separate Output Folders'
at 'Maven2 Preferences' dialog, and after turning on this
property, 'Update Source Folders' action creates source
path entries with individual output folder.

In detail, please picture the following project:
project/pom.xml
subproject1/pom.xml
src/main/java
src/main/resources
src/test/java
src/test/resources
subproject2/pom.xml
src/main/java
src/main/resources
src/test/java
src/test/resources
and assume that the default output folder is 'project/bin'.

After invoking 'Update Source Folders' action, source
folders on build path becomes like following:
project/subproject1/src/main/java
Output folder: project/subproject1/bin
project/subproject1/src/main/resources
Output folder: project/subproject1/bin
project/subproject1/src/test/java
Output folder: project/subproject1/bin
project/subproject1/src/test/resources
Output folder: project/subproject1/bin

project/subproject2/src/main/java
Output folder: project/subproject2/bin
project/subproject2/src/main/resources
Output folder: project/subproject2/bin
project/subproject2/src/test/java
Output folder: project/subproject2/bin
project/subproject2/src/test/resources
Output folder: project/subproject2/bin

In this patch, project-relative path of the default output folder
('bin') is used to generate each subproject's output folder.

I hope you accept this patch.

Takehiko, can you please respond to my comment about there separate resources would be needed? I am still not sure if it will be a good idea to have two parallel trees for Maven and Eclipse targets, especially when they all going into the same build and classpath.

As a side note, when resources are placed in a separate folder we may use resource folder as an output folder for Eclipse, so it won't even need to copy anything.

In fact, my strongest motivation to separate output folders per subprojects is to suppress Eclipse's warning messages about conflict of resources by copying into single output folder. So it may not be critical issue not to separate output folder, but lots of meaningless warning messages disturb development because they jam other important error messages up.

> As a side note, when resources are placed in a separate folder we may use
> resource folder as an output folder for Eclipse, so it won't even need to copy
> anything.

I'm sorry but I could not see what you meant. Could you please explain "use resource folder as an output folder for Eclipse" in detail?

It seems to me that Eclipse is actually rignt and you should have these properties files in a single place (perhaps common project for all subprojects), thoug I have to check some details on how Maven prepare classpath.

What I meant about target build path for resources is that you can point output folder to the same folder where sources are.

You may be right about resources for actual code, but how about resources
for testing? For example, assume that each subproject has log4j.properties
in src/test/resources folder and those contents are different from others.
I have no idea about a way to put those files in a single place.

About target build path, even if I set output folder to the same folder as source
one, the setting will be deleted after invoking 'Update Source Folder' action. X-<

Lets forget how this feature implemented now. I am just trying to understand what is the best way and still don't see how we can make it work for single project when all resources are going into the same classpath,

This action now setting output folders for resource folders to themselves. This eliminates warnings about resource conflicts even without adding property to use separate output folders. All source code still going to be compiled into single location.