Eclipse + Maven + Git + Multi-Module projects = Unhappiness

Question

We've got a multi-module project using Eclipse and Maven. The only way I could get it to work in the past was to use a flat layout for the projects, where the parent module was a peer to the other modules. This worked fine with m2eclipse and Subversion.

Now we'd like to move to Git and GitHub. I'd like to expose the entire project, along with all the modules, as a single project on GitHub. The problem is that EGit, the Eclipse/Git plugin, wants to manage projects one at a time, not groups of projects, and so if you've got a flat layout, you can't do it.

The right answer is to use a standard Maven hierarchical layout and manage the parent and all the modules as a unit. But Eclipse doesn't like that, and no amount of fiddling will get Eclipse to accept nested projects. m2Eclipse does not support hierarchies: https://issues.sonatype.org/browse/MNGECLIPSE-2291

So what do you do? Do Git from the command line and abandon the ability to see what files have changed in Eclipse? Or abandon Eclipse?

bmargulies · Accepted Answer · 2011-10-21T16:43:02.630

A standard Maven multi-module structure as a single git repo works perfectly fine for me in Eclipse Indigo with M2e and the git plugin that shows up in that environment. You can't ask Eclipse to do your fetching for you, but once you've pulled from command line, you use Team/Share, say 'Git!' and all is well.

I think I see what's the source: hierarchy is a problem for projects inside the workspace, not 'existing projects' that you import.

Here's a typical workflow:

use git svn clone to get a tree. it's a stock, hierarchical mvn multi-module tree
in eclipse, use import/maven/existing maven project. Point at the whole tree
select all
OK

it works fine. The nesting does not disturb eclipse one bit. I don't know what problem that bz is pointing at.

Before I used m2e I used the maven-eclipse-plugin. And it also worked in these cases, because it does not generate a .project/.classpath for <packaging>pom</packaging> aggregating projects, so Eclipse is never called upon to actually nest anything.

I'm not alone -- see the developer setup instructions as cxf.apache.org for an open source example that you can try for yourself.

How did you get Eclipse to deal with a hierarchical layout? I can't mine to compile. According to https://bugs.eclipse.org/bugs/show_bug.cgi?id=245412 Eclipse doesn't yet support them. — ccleve, Oct 21 '11 at 15:01

score 4 · Answer 2 · answered Oct 21 '11 at 23:22

4

Is it possible that you are working with old versions of the tool?

I have a Maven multi-module project that I work with using Eclipse 3.7 (Indigo), M2Eclipse (1.0) and EGit (1.0).

On the file system the multi-module project has a single parent directory.

In Eclipse I have separate projects for each module.

M2Eclipse does the dependency management perfectly.

There is single git repository (.git directory) at the top-level and EGit works perfectly.

answered Oct 21 '11 at 23:22

Sri Sankaran

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+1 because I was using old versions, and everything changed when I upgraded. – ccleve Oct 23 '11 at 22:36
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"In Eclipse I have separate projects for each module." For those wondering, the file system is a working hierarchy, but m2eclipse will still not allow you to manage a parent/child module as a single project hierarchy. Every module for m2eclipse has to have a project in Eclipse or else Eclipse won't find class types or relationships between them. – Feb 10 '12 at 15:28

Kane · Answer 3 · 2011-10-24T03:02:58.450

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You can put your modules in Git with hierarchical layout. And build those modules by Maven. If those modules are projects(whatever java, c++ or php project) recognized by Eclipse, they can be imported into workspace as flat layout in workspace.

-- the root of Git working directory
  -- moudule1
    -- project1(a java project)
      -- .project(a project file recognized by eclipse JDT)
      -- pom.xml
    -- project2(a java project)
      -- .project
      -- pom.xml
  -- module2
    -- projectA(a java project)
      -- .project(a project file recognized by eclipse JDT)
      -- pom.xml
    -- projectB(a c++ project)
      -- .project(a project file recognized by CDT)
      -- pom.xml

edited Oct 24 '11 at 03:02

answered Oct 21 '11 at 03:19

Kane

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How? If they're physically arranged on disk in a hierarchical way, how do you import them flat? – ccleve Oct 21 '11 at 15:02
Workspace doesn't care where the project locates(could be under the workspace or anywhere on the disk). Each project only has a .project file under the root folder, Eclipse could import it into workspace without copying it into the workspace. See my updated answer. – Kane Oct 24 '11 at 02:59

score 0 · Answer 4 · answered Nov 27 '14 at 18:18

For Maven projects, multiple imports at once can be achieved via the Maven import wizard (that is accessible from Git). In case you don't know what kind of projects you're about to import, you can use the new Easymport that will import project "as best", by deducing configurations from various files. See https://github.com/jbosstools/jbosstools-playground#easymport-easy-and-smart-openimport-of-a-project

Once you get all those projects, you can use the Nestor plugin, which will show project in a nested/hierarchical layout, mapping more correctly your Maven project: https://github.com/jbosstools/jbosstools-playground#nestor-view-nested-projects

Eclipse + Maven + Git + Multi-Module projects = Unhappiness

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