Maven Tutorial

Welcome to the introduction of Apache Maven. This tutorial aims to provide the
Maven related basic knowledge needed for working on Java projects in an enterprise environment.

The following setup is required to go through the tutorial:

• Java JDK (>=17)
• Maven (>=3)
• some IDE (I highly recommend IntelliJ)
• Git

You can start the tutorial by checking out the first git tag

git checkout tutorial_step_1

Step 1: Old school - simple

Before systems like Maven, Gradle or Apache Ant were introduced,
developers had to build their applications manually.
And that is exactly what you will start with.
There are two files HelloMavenWorld.java and Greeting.java lying in the root of the project. Nothing fancy going there. You can compile them with the command

javac Greeting.java HelloMavenWorld.java

You should end up with two class files that are named HelloMavenWorld.class and Greeting.class.
Now you can execute the main class with the command

java HelloMavenWorld

That should simply write a greeting to the console and exit.
After you are done with the very basics on to Step 2 by checking out the next git tag

git checkout tutorial_step_2

Step 2: Old school - less simple

Since you do not only care about the structure of your code but also about the structure of the files resembling your application you introduced a nice hierarchy to the classes. The two .java files can now be found in the folder

/path/to/your/projectfolder/your/company

To compile them you need to run (❗adjust path❗)

javac "/path/to/maven-tutorial/your/company/Greeting.java" "/path/to/maven-tutorial/your/company/HelloMavenWorld.java"

And once the two .class files are created you can run the application with the command

java -cp "/path/to/maven-tutorial/your/company" HelloMavenWorld

You will see a slightly adjusted message in the console.
You can now continue with Step 3 by checking out the next git tag

git checkout tutorial_step_3

Step 3: Old school - but spicy

Now you also want to bring in a third party library to spice up or ease your developer life. In the root of the project create a /lib folder and place the latest jar file of Project Lombok there. The structure should look something like this

/projectRoot
  /your
    /company
      Greeting.java
      HelloMavenWorld.java
  /lib
    lombok.jar

Lombok is used in Greeting.java to generate an immutable class with the help of the @Value annotation.
You can compile the project from the project root using the command

javac -classpath ./lib/* your/company/HelloMavenWorld.java your/company/Greeting.java

and afterwards run the main class with

java -classpath ./lib/*:./your/company/ HelloMavenWorld

As you can see this process becomes complex very fast. With just two classes and a single dependency the setup is already ugly to build and maintain . Imagine how this will look like in a big project with hundreds of dependencies (e.g. something using Spring) and thousands of classes.
So a Software Project Management tool to the rescue. In case of this tutorial it is going to be Apache Maven.

You can continue with step 4 by checking out the next state with the command

git checkout tutorial_step_4