Until now we didn’t use a repository manager for Maven. Our repos were a plain directory structure on the file system served by Apache. Uploading was done using Apache’s WebDAV capabilities with a simple authentication against our LDAP directory:
AuthName "reucon Maven Repositories"
We are maintaining four repositories: one for our public Open Source artifacts and one for proprietary internal artifacts along with corresponding snapshot repositories. Access to the internal repository was limited based on an IP address range.
There are multiple reasons for us to use a repository manager:
- Unified access to repositories
In the old days all you needed was the central repo (formerly known as ibiblio). Times have changed and now many of our projects require artifacts from a variety of different repositories. It seems many organisations prefer having their own repos instead of publishing to central. This includes SpringSource, JBoss, Codehaus and several snapshot repos like for Apache. Maintaing a list of these repos in each developers settings.xml is a pity and including them in the poms makes things even worse in the long run.
- Finer grained access control
On the one hand we need access to our internal repo from outside of our internal network, so IP based access control no longer works well. On the other hand not all developers should be allowed to publish releases. Some kind of role based access control was needed.
- Automated creation of the Nexus index
A Nexus index is basically a zip file containing a lucene index of the artifacts in a repository. Most Maven IDE plugins now support searching for artifacts when adding dependencies to a project. To make this work the IDE must be be able to download an up to date index of the repositories.
- Web based artifact search
You may know mvnrepository.com a web site to search for artifacts in the central repo. I’ve often used it to find the correct version and maven coordinates for a dependency. A similar solution for our internal repositories would be nice.
There are a lot more reasons to use a repository manager like faster builds through caching of artifacts, black- or whitelisting of artifacts based on corporate standards but those listed above were the key factors for us.
There are three products that can be used: Apache Archiva, Sonatype Nexus and JFrog’s Artifactory. There is a feature matrix
that shows their features.
I dropped Archiva because its development is rather slow and it is missing some important features like grouped repositories. So Nexus and Artifactory remained. I came across two blog postings from January:
Sonatype’s comparison and
JFrog’s response. Combined they provide a lot of insight. Here is my own comparison:
Good LDAP integration is a must have. Artifactory supports this out of the box, Nexus does not include LDAP support in its Open Source edition. It is a Nexus Pro feature. I do understand that Sonatype is trying to sell its Pro version but LDAP support is really a basic and vital feature. Fortunately it is not too difficult to implement a custom authenticator for Nexus and in fact there is already a project at Google Code called nexus-ldap that adds free LDAP support to Nexus. Both Artifactory and Nexus support fine grained role based authorization. One problem I faced with Artifactory was that requiring authentication seems to be a global setting, so you either require authentication for all repositories or for none. This is less flexible than Nexus which allows us to make our Open Source repository available without authentication and requires authentication only for deployment and for our internal repositories.
Artifactory has a nice additional feature that eliminates the need to store the user’s password in Maven’s settingx.xml in clear text by encrypting the password with a user specific key stored in Artifactory. This is an interesting approach and I would like to see this concept being used more widely (e.g. for Subversion).
How the repository manager stores artifacts and meta data is the biggest difference between Artifactory and Nexus. Artifactory uses a Java Content Repository (JCR) that can optionally be hosted in a MySQL database.
Nexus stores artifacts and meta data in the file system. It uses the maven layout so it is easy to access the repositories managed by Nexus externally. This becomes handy not only for migration but also when synchronizing to central through rsync. Though Artifactory offers an export feature having my repository data available directly on the file system makes me feel better.
Searching and Indexing
Both Nexus and Artifactory publish indexes (based on Lucene) and provide a web interface for searching artifacts stored in the repository. Nexus takes this one step futher and also allows searching for artifacts in proxied repositoreis not yet stores in the local repository. This is really handy and eliminates the need to use external sites to search for artifacts and they current version.
Before I found nexus-ldap I was about to choose Artifactory over Nexus. After that I prefer Nexus for the file system based storage and better searching.