Get dependencies from multiple repo's - maven

Is it possible to download dependencies in maven using multiple plugin-repos?
I have my settings.xml configured to get dependencies from a custom repo and because of this, i am unable to get dependencies from the main maven repo server.
Is this possible to setup more then one plugin Repo?
Here is what i have setup so far for my custom repo:
</profiles>
<profile>
<id>custom-config</id>
<repositories>
<repository>
<id>custom-snapshots</id>
<name>customSnapshots</name>
<releases>
<enabled>false</enabled>
<updatePolicy>always</updatePolicy>
<checksumPolicy>warn</checksumPolicy>
</releases>
<snapshots>
<enabled>true</enabled>
<updatePolicy>never</updatePolicy>
<checksumPolicy>fail</checksumPolicy>
</snapshots>
<url>http:/custom/repo</url>
<layout>default</layout>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>custom-plugins</id>
<urlhttp:/custom/repo/public-snapshots</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</profile>
</profiles>
I have not included the dependencies here, but I am unable to pull and resolve some library dependencies.
The maven repo that I use is http://mvnrepository.com/ but I dont have details on the exact repo settings to use as the one I defined for a custom one.

The default maven repository is called "central". Its url is: http://repo1.maven.org/maven2/ or nowadays: http://repo.maven.apache.org/maven2/
But it is usually configured as mirrorOf. If you create a repository in your settings.xml and give it the id *central" it will replace it.
So I wonder why you can't resolve dependencies from there. Usually adding a repository in settings.xml does not turn of central.
could you execute mvn help:effective-settings and mvn help:effective-pom and have a loook at all repositories, profiles and mirrorOf elements in the xml? central should be there.
I would also recommend using a Maven proxy like Nexus or Artifactory. It simplifies a lot of things within a company.

Related

Specify Maven plugin repository from the commandline

I want to use maven's dependency:get to download a package. I need to configure both a remote repository and a plugin repository. If I configure it in settings.xml it works:
(Example settings.xml from https://maven.apache.org/settings.html)
<profiles>
<profile>
...
<repositories>
<repository>
<id>codehausSnapshots</id>
<name>Codehaus Snapshots</name>
<releases>
<enabled>false</enabled>
<updatePolicy>always</updatePolicy>
<checksumPolicy>warn</checksumPolicy>
</releases>
<snapshots>
<enabled>true</enabled>
<updatePolicy>never</updatePolicy>
<checksumPolicy>fail</checksumPolicy>
</snapshots>
<url>http://snapshots.maven.codehaus.org/maven2</url>
<layout>default</layout>
</repository>
</repositories>
<pluginRepositories>
...
</pluginRepositories>
...
</profile>
</profiles>
...
</settings>
mvn dependency:get -Dartifact=<artifact>
However I would like to be able to do this without configuring the settings.xml file. I know dependency:get lets you specify a -DremoteRepositories argument. There there any way to specify the plugin repository? In my particular case both repositories are actually the same location however if I only provide -DremoteRepositories maven fails to download the plugins.

How maven handle multiple <repository> configurations?

I am getting more and more comfortable with maven. But still some questions.
I have multiple <repository> in my pom.xml.
How will maven handle these repos when downloading artifacts? Will it search by the declaration order?
Besides the explicitly declared ones, will maven still check the default central repo at http://repo.maven.apache.org/maven2/?
If something cannot be found within the explicitly configured repo, will maven fallback to the default central repo?
Is it good to use multiple repos? I am kind of worried about inconsistency.
Below is the <repositories> section of my pom.xml:
<repositories>
<repository>
<id>ibiblio-central-repo</id>
<layout>default</layout>
<name>ibiblio-central-repo</name>
<releases>
<checksumPolicy>warn</checksumPolicy>
<enabled>true</enabled>
<updatePolicy>never</updatePolicy>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
<url>http://maven.ibiblio.org/maven2/</url>
</repository>
<repository>
<id>oschina-central-repo</id>
<layout>default</layout>
<name>oschina-central-repo</name>
<releases>
<checksumPolicy>warn</checksumPolicy>
<enabled>true</enabled>
<updatePolicy>never</updatePolicy>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
<url>http://maven.oschina.net/content/groups/public/</url>
</repository>
<repository>
<id>oschina-central-repo-3rd-party</id>
<layout>default</layout>
<name>oschina-central-repo-3rd-party</name>
<releases>
<checksumPolicy>warn</checksumPolicy>
<enabled>true</enabled>
<updatePolicy>never</updatePolicy>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
<url>http://maven.oschina.net/content/repositories/thirdparty/</url>
</repository>
</repositories>
How will maven handle these repos when downloading artifacts? Will it
search by the declaration order?
Order of declaration as part of the merged settings (see next answer). I have found this JIRA ticket providing further details.
Besides the explicitly declared ones, will maven still check the
default central repo at http://repo.maven.apache.org/maven2/?
Yes, as it will be provided by the Maven super POM, implicit parent of all Maven Pom (here an official example), unless specified in your settings.xml (if you override the repository id specified in the super POM). You can use the Maven Help Plugin to get the effective settings Maven will apply to your build and the effective pom maven will actually (effectively) run.
As documented here, the repositories element is inherited.
If something cannot be found within the explicitly configured repo,
will maven fallback to the default central repo?
As above. Moreover, you could also influence this mechanism via any configured Maven mirror. You could, for instance, redirect Maven to your company repository (see below) instead of looking up on the default one.
Is it good to use multiple repos? I am kind of worried about
inconsistency.
You probably don't need many configured repositories, but you might need more than one if the dependencies you are looking for are not provided by the default repository. A good approach would be to have an enterprise Maven repository (i.e. Artifactory, Nexus) and make your local settings only point to it. Then, configure the internal Maven repository to point to other repositories, in a centralized (and governed) manner.

Getting "Missing Artifacts" while they are exist in .m2

In my setting.xml from .m2 folder, the following configs are applied to get jar files from local nexus repository:
<mirrors>
<mirror>
<id>nexus</id>
<mirrorOf>central</mirrorOf>
<url>http://192.168.0.172:9090/nexus/content/groups/public/</url>
</mirror>
</mirrors>
<profiles>
<profile>
<id>nexus</id>
<repositories>
<repository>
<id>central</id>
<url>http://central</url>
<releases>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</releases>
<snapshots>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>central</id>
<url>http://central</url>
<releases>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</releases>
<snapshots>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</snapshots>
</pluginRepository>
</pluginRepositories>
</profile>
</profiles>
<activeProfiles>
<activeProfile>nexus</activeProfile>
</activeProfiles>
In my pom.xml, an external repository declared to get jar files not presented in central repository:
<repositories>
<repository>
<id>spring-snasphot</id>
<url>https://repo.spring.io/snapshot</url>
</repository>
</repositories>
Despite of the fact that these so called "missing artifacts" are existed in their corresponding folder in .m2, but I always get
Missing artifact ....
What is wrong with my configurations?
Thanks in advance.
Finally I just figured it out. Having deleted files excluding jar file from corresponding folder, and then updating maven project solved the problem.
The configuration looks ok. But something must be going on...
If you delete those snapshot artifacts from your local repository and retry (for ex: mvn dependency:go-offline) do you see an attempt is made to download the artifact from https://repo.spring.io/snapshot ?
The additional repository seems to contain snapshots but the are not enabled for that repository. But I'm not sure whats the default. The artifacts may be not found because of the update policy. They are locally available but too old so maven tries to update them but fails (have you tried mvn -X ? that may give an indication what fails when resolving those artifacts).
What may be an option is to add the spring snapshots repo to your nexus (snapshot repo enabled) and set the mirrorOf in settings xml to <mirrorOf>*</mirrorOf>.
The mirror of central only might was intended so: just an experiment :)
It is always a good thing to verify the settings maven actually sees are the ones you think they are:
mvn help:effective-settings
mvn help:effective-pom

Difference between repository and pluginrepository

My Android Maven project pom.xml contains the following entries. Now everything works fine. What is the difference between <repositories> entries and the <pluginRepositories> entries.
<repositories>
<repository>
<id>my-repo</id>
<url>http://10.10.10.230:8081/nexus/content/groups/public</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>my-repo</id>
<name>my-repo</name>
<url>http://10.10.10.230:8081/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
As #otakun85 stated, There is no technical difference at all. It's for having different configurations->behavior for plugins in contrary to normal artifacts. See repository vs. pluginRepository for more details.
Also check maven-users mailing list archives, It provides quite good explanation to it.
Maven will resolve plugin dependencies using the configured pluginRepository. Other artifact dependencies (eg. a parent pom) are resolved using repository.
Note: Things available on maven central will be resolved by default so you wouldn't normally need to include repository for those.
For example, if your pom.xml specifies a parent pom and a plugin dependency that both exist in the same repository you must still specify both repository AND pluginRepository. If you only configure one then maven will complain with "Unresolvable X" errors.

Maven repository lookup order

We have an internal Apache Archiva based repository and we have configured the repositories tag in pom.xml to be as follows. Can I assume that all dependency access will get resolved by internal repository if you have access to it and will get resolved by other repositories listed below, if internal repository is down for a certain reason.
<repositories>
<repository>
<id>internal</id>
<name>Internal Repository</name>
<url>http://192.168.1.2/archiva/repository/internal</url>
</repository>
<repository>
<id>jboss</id>
<url>https://repository.jboss.org/nexus/content/repositories/releases</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
....
</repositories>
EDIT:
I want to do away with the .m2/settings.xml file. I want to define this in my pom.xml file, so that if my repository manager is UP and running I would want the runtime to connect there, else would want to fallback into the other repositories. Would this be possible?
Maven 3.0 had it fixed as you can see in Maven developer's Jira below. The lookup will be done in the order they are declared.
https://issues.apache.org/jira/browse/MNG-4400

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