maven – Nikolay´s Technical Blog

Sooner or later, after a couple of reinstallations of the operating system, each of us reaches the conclusion that the user applications should be installed to a partition/hard-disk, different from the system one. On the other hand, the default configuration of most of the applications by default rely on the fact that the installation of that program is done on the system partition (at least under Windows). That’s the case of Eclipse and Maven as well.

Changing Maven Local Repository Location

Even Maven to be installed on a partition different from the system one, by default the Mavel local repository is expected to be on the system partition:

for Windows (Vista/7) it is at C:\Users\<WINDOWS_USERNAME>\.m2\repository
for Linux – at ~/.m2/repositoy

If we want to change the local repository location, to be on a partition other than the system one for example, the only what is needed is to be changed the Maven configuration file – settings.xml, located in the Maven installation directory. For the purpose, uncomment the tagg localRepository and add the path to the new directory, which will be used for new local repository:

<settings>
...
<localrepository>/path/to/local/repo/</localrepository>
...
</settings>

In my case, the change looks in the following way:

<settings>
...
<localrepository>D:/config/maven/.m2/repository</localrepository>
...
</settings>

Eclipse and the New Maven Location

By default Eclipse uses its own Maven instance. For local Maven repository, it uses the following folders:

for Windows (Vista/7) at C:\Users\<WINDOWS_USERNAME>\.m2\repository
for Linux at ~/.m2/repository

If we install Maven in a location different from the one by default and we configure the local repository to be on a directory different by the one indicated by default, what we could expect is the installation of the generated by Maven archives (jar, war, etc.) in the local repository, to be placed on the newly defined place.

If we don’t reflect these changes in Eclipse, it will use its own Maven installation and its own configuration for the local Maven repository. Respectively, if Eclipse does not find the folder.m2/repository in the current user’s directory (user.home) usually on the system partition/hard-disk, Eclipse creates that folder and install the generated archives for the built Maven projects in it. Thus, the building and installtion (in the terms of Maven) of the same projects from the command line and Eclipse will cause the creation of archives on two different locations.

Moreover, not always the Maven version, which Eclipse uses (M3 in the case of Eclipse 3.6.1 for example) coincide with the one, which is used for the current project (M2 for the project, which I am working on at the moment). As we know, because of the improvements of Maven in version M3 with regards to the optimisation of its performance, the Maven projects, built with this version are incompatible with M2 and vice versa.

So, we can isolate the following problems when we change the local Maven repository and installation, but not reflecting this change in Eclipse:

Again we save user generated files on the system partition/disk (the ones generated by Eclipse).
We don’t have synchronization when we build and install the Maven projects through the command line and the IDE (the projects built and installed via the command line does not bring changes in Eclipse).
It’s possible the archives generated via command line and Eclipse to be incompatible.

In order to avoid all these drawbacks, is required to apply two changes to the Eclipse default configuration. Open the menu Window > Preferences and change:

Indicating in Eclipse to use the new Maven installation: Maven > Installations > Add... and chose the directory, %MAVEN_HOME%, which points to the new Maven installation and which will be used through the command line.
Configure Eclipse to use the new Maven repository: Maven > User Settings > User Settings > Browse and chose the location indicated in settings.xml configuration file of Maven, which describes where is located to the new local repository (explained in the prvious section).