Develop Reference

Consume / import local fat jar as plugins in maven

I have recently used the Maven Assembly Plugin and also the Maven Shade Plugin in order to create a FAT JAR containing a specific plugin and its dependencies.
I did this because during the build phases our company uses private servers with no access to the internet so I can't depend on public repositories.
So I have this FAT-JAR-WITH-DEP.jar and to test if it works with my module, I removed the original plugin jar from the maven repo and pasted this instead.
I also removed its dependencies. the POM file remained the same.
What happens is that it still tries to download the dependencies because of the pom file.
How do I use a FAT JAR as a plugin that already includes it's dependencies?

Sorry, but building such a fat jar is not a good idea. You are trying to manipulate the "inner structure" of Maven.
If you want to use Maven in an offline environment, copy all the relevant plugins and dependencies to your company Nexus/Artifactory. The easiest way to do this is run a build once against a public repository and then copy all the stuff that was downloaded through Maven.

Loading maven dependencies from local Git server

We are using our git server for project management. How do I download maven project dependency from my git server?
For project checkout/pull and push we are using tortoise git
Clarification:
We are using another project as a submodule in our project. That project available on our local git server. So, when the new update is available I have to download and copy in m2 repository manual. Instead of a manual process, I want to download from my local git server.

Storing jar artifacts in git is a bad idea. Git is not meant for binary files. Use a maven repository server like Nexus or Artifactory instead.
EDIT: I admit that this answer lacks background and explanation. So I added a little.
Most sources I know do not recommend to put (large) binaries into git repositories because checking out the git repository means checking out all old versions of the binaries and that might be a lot of stuff.
There are specialised solutions (Maven repositories like Nexus/Artifactory) for the task at hand which can be directly used by Maven without giving URLs to separate artifacts (the URL of the repository suffices to find all artifacts in it).
AFAIK GitHub and GitLab offer services to provide Java artifacts as Maven repositories. So if you use on of these services, you probably have cheap other option.

How include 3rd party jars in maven project (compile, build, package) where adding local maven repo is not an option?

We have a git project that has some 3rd party jars which are not available in any Maven repo and are in a "lib" folder in the project. I need to include them for compiling, building and then package them into the WAR in WEB-INF/lib.
I cannot add them as a local maven repo from the command line because this projects needs to be buildable for anyone cloning the repo without requiring them to run extra commands (I have no way around this requirement).
I saw some people suggesting System scope but that then Maven won't package them into your WAR:
<dependency>
<groupId>com.roufid.tutorials</groupId>
<artifactId>example-app</artifactId>
<version>1.0</version>
<scope>system</scope>
<systemPath>${basedir}/lib/yourJar.jar</systemPath>
</dependency>
How do I get these jars to be used for compiling/inspection, building and then packaged into the WAR?

You can use :
System scope but make the packaging yourself via assembly plugin
A maven repo along with your project (i.e. maven repo on-the-fly, basically same as local repo but without having a extra moving part to worry about because this repo follows your project).
For Maven repo on-the-fly option, you can do as described here (which is, take any already existing Maven repo, which already contains your needed jars, such as your local one, put it in your project, and then reference this repo from your project using relative paths).

I'll assume you've verified that whatever mechanism you might use to distribute these jars would be in compliance with the relevant licenses. If it would, then it seems there would be little reason for the jars' creators not to provide for official Maven distribution, so your best option might be to lobby for them to do that. But if not, and yet for some reason they'll allow for you distributing the jar (either through cloning of your repo, or via a separate Maven repo you maintain):
There are several ways. I give preference to approaches that don't put the jars in the git repo.
Publish a Maven Repo
So it's possible to host a public-facing repo and serve the artifacts that way. The pom can add your public-facing repo to the build, so that those who clone can build without having to run any special commands.
Running your own repo isn't terribly difficult. The OSS versions of Nexus or Artifactory jFrog would probably be perfectly capable.
But, if we're assuming the authors' refusal to publish their own jars via Maven means they don't want them distributed that way, then there's no reason to spend much time on the details of this option. So moving on...
Distribution in the Git Repo
I guess this is what you're doing, though again if Maven distribution violates the license I'd make sure you're splitting hairs the right way in thinking that this doesn't.
So the question would be how to get Maven to deal with the artifacts distributed in this way, and again there are some options.
Your objection to putting the jars in the local repo is that it would require extra commands of the user; but actually this could be automated in the "validate" phase of the build. Binding install:install-file to the validate phase should work.
Alternately, your objection to using system scope is that the file isn't copied into the final war. You might be able to use the dependency plugin to force the issue, but I'm not sure of that. What I am sure of is you could treat the directory containing the jars as a web resource with suitable configuration in the war plugin. (You'd want it to be treated as unfiltered and to map to the WEB-INF/lib folder.)
In any case, if you distribute jars (or other large binaries) in the git repo, I strongly recommend you look at git lfs. This will require one-time configuration by each of your users, but it will prevent your repo from gradually becoming bloated and unusable.

Use forward slash (/) to backslash () in the systemPath.
<dependency>
<groupId>com.roufid.tutorials</groupId>`enter code here`
<artifactId>example-app</artifactId>
<version>1.0</version>
<scope>system</scope>
<systemPath>${basedir}\lib\yourJar.jar</systemPath>

Install Library and Its Dependencies From Maven Repository Into Internal Repository

Question
I have an internal maven repository in a shared folder say s:\mvnrepo – it's just a convention for a directory layout after all. Now I want to install a library com.example.lib:lib:1.0.0 and its dependencies from another external maven repository into s:\mvnrepo with the hypothetical command
mvn installlib com.example.lib:lib:1.0.0 -Dinto=file:///s:/mvnrepo
That would be a dream! Is such a thing possible?
(I don't have high hopes seeing as everything maven related is always so unapproachable and complicated...)
Supplemental Information
Now, I know there are maven repository management systems like Nexus but I really do think my use case should not require them. I also know about the deploy-file goal but it doesn't install transitive dependencies into the specified repository.
I also thought about simply creating a dummy project that has the specific library listed in its pom.xml. Then just execute mvn install -Dinto=file:///s:/mvnrepo. The problem is that the install goal apparently does not have an option to specify the repository directory (i.e. -Dinto is purely hypothetical).
I found out that it is possible to download a library and all its dependencies with Intellij. That's great but Intellij really only downloads the jars and does not create a maven compatible directory structure (i.e. there are no poms downloaded nor are the jars in a group subfolder etc.).
Background information
For work we want to have an internal maven repository such that it is possible to build an application on a freshly installed server that does not have an internet connection while still being able to specifiy dependencies in the gradle file as if we would use an external maven repository like jcenter (resp. bintray). So the gradle file we use would look something like this:
repositories {
// jcenter() // we don't want that
mavenUrl 'file:///s:/mvnrepo'
}
dependencies {
compile 'com.jakewharton.sdkmanager:gradle-plugin:0.12.0'
}
Now, I downloaded the sdkmanager plugin jar and its pom file from mvnrepository.com and used something like
mvn deploy:deploy-file -Dfile=sdkmanager.jar -Dpom=sdkmanager.pom -Durl=file:///s:/mvnrepo
All fine and dandy, the sdkmanager plugin is installed into s:\mvnrepo with the correct directory layout and gradle even picks it up! But gradle is not quite satisfied, you see. It demands the jarchivelib which is a dependency of com.jakewharton.sdkmanager:gradle-plugin:0.12.0 (see the page on mvnrepository.com where jarchivelib really is listed as a dependency of the sdkmanager plugin). Now, I could repeat the fun and download jarchivelib and its pom from mvnrepository.com, deploy it and so on. Thinking about it... that does not sound like fun at all! So now you see my concrete use case and maybe you could suggest an even better approach than what I seek for in my question.

How to create local Maven repository for hosting non-Mavenized libraries?

Here's the problem: I love using Maven, as it completely simplifies development and dependency management. However, I'm working with a server which isn't Mavenized, so I can't just add it as a provided dependency. Is there a way to simply specify an additional library folder and add it to the Java compiler classpath, or would I need to actually create an entire local Maven repository for this? I know it completely limits my portability, but I'm okay with that. Thoughts? Also, after compiling, I'll need to copy all of my non-provided dependencies to the local server lib directory, I assume I can use the copy-dependencies plugin to move everything over.

Download Nexus for free from Sonatype, or Artifactory, or any of the other repository managers.
The alternative is to learn about install:install-file to shove jars into your personal local repo. However, having a full repo as above has so many advantages (not the least speed via caching) that it's easier to just install one.

You can use a Maven2 repository implementation such as Nexus, Artifactory, or Archiva.
You can create a simple POM for the non-maven dependency you are working with and use the deploy:deploy-file goal to deploy it to the repository.
If you just need the dependency locally you can use the install:install-file to install the dependency in your local repository. This approach requires nothing more than maven be installed on your machine.
If you just want to add libraries to the path of your build without worrying about repositories you can declare them as system dependencies. I do not recommend this approach but it should work fine.