Are both the things are doing the something different or not?
As the second one, when you right click on any maven project on eclipse go to Maven and then Update project.
First is pretty much clear that it clean and artifacts from target and generate the artifacts into target and local repository.
In the first case, you start Maven to build a jar/war/ear and install it in your local repository. It is Maven mechanism. It also updates your dependencies through the -U flag.
In the second case, you start a procedure of the m2eclipse plugin that updates you dependencies. It will not write any artifacts to your local repository. It also does not run a full build.
Related
I have a project A and B. Project B uses project A as a dependency. I am publishing project A to Nexus repository when changes are tested and good to go to Nexus. However I don't want to publish project A to nexus whenever I want to test changes locally.
Is there a way to use project A's changes locally into project B without having it to be read from repository. Some condition that will make maven read project A from local rather than Nexus.
I want to keep project A in common maven dependencies rather than making changes in Maven profiles.
Maybe I am missing some obvious point but I would assume that you can just mvn install project A with a new version and adjust the dependency of A in project B to use that new version. By installing project A it should be available to be used in project B locally because it will be installed into your local Maven repository.
E.g.
In project A's pom.xml
<project>
<name>A</name>
<version>1.1.1-new-version-for-testing</version>
</project>
In project B's pom.xml
<dependencies>
<dependency>
<artifactId>A</artifactId>
<version>1.1.1-new-version-for-testing</version>
</dependency>
</dependencies>
First things first, there is a local repository on your computer that contains all the dependencies (by default in ~/.m2 but you can change that)
You can think about it as a local cache of the dependencies required to work with your own project
When you change the project A you can install the "updated" version by running mvn install on project A.
After that command project B when tested will not try to contact maven repository and will get a version of project A from your local repository.
For SNAPSHOT dependencies, maven once in a day will try to get the later version from Nexus anyway, even if you have a copy in the local repository, because working with snapshots assumes that you're OK with getting daily changes.
But then you have the following choices:
Don't work with SNAPSHOT-s at all. This is something that you shouldn't do anyway in production (I mean, when you release project B, it should contain SNAPSHOT dependencies in its pom)
When you compile project B, assuming you have all the dependencies in the local repository, use mvn <whatever> -o. This -o option means that maven should be run in offline mode, that is it won't attempt to contact a remote repository altogether. (BTW, If you want to do the opposite, which is to forcefully download all new dependencies from Nexus, you can run mvn <whatever> -U
I have a Maven project that works just fine.
In order to triage an issue, I manually patched a jar to add debug logging and then copied it to the local Maven repo directory. I made subsequent changes to the jar file to add more debugging and did a mvn install:install-file since that seemed more "official".
Note that I did not change the coordinates at all (I know that artifacts are meant to be immutable, but I did not want to change pom.xmls).
My question is: when (if ever) will Maven overwrite this patched jar with the one in the remote Maven repository which is considered the source of truth?
There are only three scenarios in which that jar can be overwritten:
If you delete the jar from your local m2 repository, it will be downloaded from the remote repository the next time you build your maven project.
If you build your maven project with '-U' option. Doing this will force maven to update the dependencies from remote repository.
If you perform an mvn install on the same artifact(updated code) with the same version.
I am new to maven and I heard the term "maven clean repo" building ? What is the meaning of this ? How it different from the normal maven building process ? Also I want to know about the maven repository and how it changes when we build the software
I'm not sure if there is an exact term called "maven clean repo building" - but it is probably referring to doing a clean build by clearing out your entire LOCAL maven repository to ensure you have only the correct dependencies for your project.
All dependencies you need get downloaded into the repository which is at ${user.home}/.m2/repository by default. You can see this grows as the build runs and dependencies get downloaded into this folder.
The link
http://maven.apache.org/plugins/maven-dependency-plugin/examples/purging-local-repository.html explains one way of purging this.
You can change the maven repo being used for the build by providing the following argument to the build command
mvn clean install -Dmaven.repo.local=/tmp/sampleRepo
If relevant artifacts are not available in the pointed maven repo, it will download them from relevant repositories (maven central or repositories which are provided in the pom.xml file).
Hint;) Using a directory in /tmp/ will be more good as /tmp/ get automatically cleared in OS restart.
When running mvn install on a local multi module project it builds and install the projects artifacts into the local repo. mvn clean seems to clean up my project specific target directories.
What command do I use with maven to get it to uninstall my projects modules from the local repo? for example my projects outputs foo-0.1.jar and bar-0.2.jar I want those removed from my local repo without having to go in there and delete them myself.
mvn build-helper:remove-project-artifact
You can purge artifacts from your local repository, but why do you like to do this? Apart from that you can do that via maven-dependency-plugin:
This will purge all project- and dependency artifacts
mvn dependency:purge-local-repository -DreResolve=false
This can be influenced by supplemental command line arguments (see the documentation) for further details.
Best is to implement a release strategy, i.e. as long as the artifacts under development appending the version with SNAPSHOT. Maven then automatically updates the artifacts in the local repository when you run install. Once you have completed the development you remove the SNAPSHOT and release the version (i.e. via deploy). If further development is required you could increase the version number and append it again with SNAPSHOT.
My situation: I have project which contains several Maven modules. I make changes to one of them. Suddenly I find out, that my project is no longer possible to be built because of the errors in other modules. To fix this I need to run SVN UPDATE and rebuilt the project.
My assumption: probably, during the build process of my module some of the artifacts are taken from central repository and have the most newest version, while others are still outdated and taken from my local repo.
A question: I don't want to rebuild my project each time someone updates ANOTHER Maven module. I want to download the already built artefacts from the central repository without rebuilding them by myself. Is it possible?
You can tell Reactor which modules to build. In your case when you only change a single module and want to speed up the build you can pass -pl (Project Location) parameter to maven. For example:
mvn -pl module-with-changes
That will build single module, while taking other dependencies from your local Maven Repository or download from Central (whatever is the latest). That said, if you already ran mvn install for whole project and other artifacts have not been updated in Central repository, then Maven will see your local artifacts as latest and will not re-download them.
Another issue you might get with -pl parameter is when other modules in your project depend on the module that you are building. If there is a problem in dependent module you will not see it by building only the dependency model. To avoid that you can pass -amd (Also Make Dependents). Like this:
mvn -pl module-with-changes -amd
That will trigger the build for module-with-changes + modules that depend on module-with-changes + their dependents.
You can get more info about Reactor parameters from here:
http://www.sonatype.com/people/2009/10/maven-tips-and-tricks-advanced-reactor-options/