Develop Reference

How to configure classpath for maven exec:java?

How to add some local folders to the classpath when executing using maven exec:java? Each folder contains multiple jars, so I prefer not to add each jar separately.

Take a look at the Apache Maven Install Plugin: http://maven.apache.org/plugins/maven-install-plugin/index.html
You can use the install-file goal (http://maven.apache.org/plugins/maven-install-plugin/install-file-mojo.html) to install your external jars to your local maven repository and then include them as normal maven dependencies.
Take a look at this tutorial: http://www.mkyong.com/maven/how-to-include-library-manully-into-maven-local-repository/

I thought you could use
addjars-maven-plugin
to configure each of your directories and set the goal as
add-jars

Adding a local jar into mvn clean package result

I'm building a SonarQube plugin and I need to use Maven to achieve it, I must use the goals clean package to create the jar file that acts as the plugin. My problem is that I need to load either a local jar file, which didn't worked as I tried using: <systemPath>${project.basedir}/lib/epsilon-1.3-core.jar</systemPath> to load it as a dependency and Maven wasn't able to resolve it or I must load three external projects which are at my workspace but I don't know how to tell maven to include them.
Could someone help me to do this? I'd really appreciate it! Using my own Maven repo (with Nexus for example) isn't an option.

I had to do a local maven repository loading the plugins of Epsilon as jar files, it's a temp solution while the Epsilon Team setup a maven repo.

How to add dependencies for maxmind geoip2 eclipse

I'm trying to use MaxMind's GeoIP2 database, I've added the jar to my Java build path and configured it with Javadoc and source but when I run the program I get a NoClassDefFound error, which according to this stack overflow answer is because I need to add the dependencies, but I have no clue how to add them in eclipse, I tried extracting the jar files and adding them to the build path but that didn't work, how do I do this in eclipse?
Thanks for any help.

In eclipse you have to create a new maven java project. If you dont know maven you can get informations here:
apache maven startsite
how to install maven
Afer that you are able to configure your dependencies in your pom.xml file. Which is the configuration file for maven.
You can find some dependencies for your usage here:
maxmind documentation
The include of the dependency would look like this:
<dependency>
<groupId>com.maxmind.geoip2</groupId>
<artifactId>geoip2</artifactId>
<version>v2.3.0</version>
</dependency>
But first, you should look at maven installation and using. It will make your life easier by handling all the necessary dependencies you will need in this project and in all of your other projects in future.

You don't need to use Maven
For Eclipse, you may use Rightclick on Project > Properties > Java Build Path > Add External JARs. Select the JAR file you downloaded.

How to include maven-based project into my non-maven project

I have a non-maven app engine project. I need to include the following library/project into it: https://github.com/UltimaPhoenix/luceneappengine. Without using maven at all, how do I make this work? I need step by step details. I have been trying and my code will not even compile. I am using eclipse.
Looking at the pom.xml I have figured that I need to download luceneappengine, which I did at http://search.maven.org/#search%7Cga%7C1%7Cluceneappengine. Do I need any other jars?

First of all, download Maven to be able to build the project. After that, just use "mvn install" to produce the *.jar of luceneappengine (the result will be stored in the "target" folder of the project). However, it will probably need some extra dependencies. To obtain them, use "mvn dependency:copy-dependencies -DoutputDirectory=$TARGET_DIRECTORY". This command will download all the required jars into the specified $TARGET_DIRECTORY.

Ant use Maven's library

I wrote a project which use maven. It's good for me.
But, some other people don't have maven, so I am trying to write an ant build.xml for them.
My question is:
Inside "javac" -> "classpath" tag, how could ant get the libs I used in the project from maven? So that could compile & pack all the 3rd-party libs into release via ant.
Is this possible or there are better solution for maven & ant exists in same project.

Ant combined with Ivy is your answer. Ant can use a Maven repository to pull in jars, and can even be made to output a pom.xml, so the jar can be deployed back to a Maven repository.
I have an ivy.dir project on Github that I use to help integrate Ivy into already existing Ant tasks -- especially if they use Subversion as a version control system. You can create a ivy.dir subproject, and make that an external on the Ant project.

Have a look at ivy. Use it to download your dependencies for ant from a maven repository.