A Practical Introduction to Maven Build Tool

1. What is Maven?

Apache Maven is a build automation tool used to generate artifacts such as .jar, .war, and .ear files. It is primarily used for Java projects.

Maven helps automate the complete software development lifecycle, including:

• Compiling source code

• Running tests

• Packaging the application

• Deploying the artifact to a repository or server

Note: pom.xml is the main file for all Maven-based projects it acts as the heart of the build system

Why Do We Need Maven?

Suppose you clone a Java project from GitHub the code is just a collection of .java files (source code).
But you cannot deploy raw source code to a server like Tomcat or JBoss.

You need to:

1. Compile the code

2. Download required libraries (dependencies)

3. Run tests

4. Package it into a deployable .jar or .war

5. Optionally push it to a repository (e.g., Nexus)

• Doing all of this manually can lead to errors and takes a lot of time.

• This is where Maven helps it automates everything from build to deploy.

Key Features:

• Open Source – Maintained by the Apache Software Foundation

• Cross-Platform – Works on Linux, Windows, and macOS

• Convention over Configuration – Reduces setup and boilerplate

• Dependency Management – Automatically pulls required libraries

• Extensible with Plugins – Test, package, deploy, report, and more

• Standard Directory Structure – Easy to understand and maintain

Build Tool by Language

• Java: Ant, Maven, Gradle

• Python: Pybuilder

• .NET: Nant, MSBuild

• Ruby: Rake

• Go: Go build tool

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2. JAR, WAR, EAR – What Are They?

When you write Java code, after compiling and building, you get a package called an artifact.

There are 3 common types:

1. .jar – Java Archive

• Standalone Java Applications

• A .jar file is a compressed archive (similar to a .zip file) that contains compiled Java code.

• All .class files (Java bytecode), which are generated by compiling .java source files, are bundled together.

• It may also include:

• Configuration files like .properties or .xml

• An optional metadata file: META-INF META-INF/MANIFEST.MF

Purpose:

• To package and distribute Java programs easily.

• Allows running Java applications directly from the command line:

Key Point:

• A .jar file is like a container for Java logic.

• It does not typically include web content like HTML or JSP files.

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2. .war – Web Application Archive

• Used for: Web Applications

• A .war file is a compressed archive used to package:

• Backend Java logic (.class files, servlets)

• Frontend files (HTML, CSS, JavaScript, images)

• These are all bundled into a single .war file for deployment.

• Contents of a typical .war file:

• WEB-INF/ folder

• web.xml (deployment descriptor)

• Compiled .class files

• Static files like index.html, style.css, script.js, images, etc.

Deployment:

You deploy a .war file to a Java application server like:

• Apache Tomcat

• JBoss

• GlassFish

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3. .ear – Enterprise Archive

Used for: Big Enterprise Applications

• In real-world big projects (like banking or government apps), you need multiple modules:

  • Web Module (.war)

  • Logic/Service Module (.jar)

• These are combined together into .ear

• .ear = .war + .jar (multiple modules together)

Deployed to heavy enterprise servers like:

• JBoss

• WebLogic

• WebSphere

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3. Apache Maven Installation on EC2 (Red Hat)

System Requirements

• Maven Version: 3.9.x or above

• Java Requirement: JDK 8 or higher (Java is required before Maven)

• EC2 Instance Type: t2.micro is sufficient

• Memory: No specific requirement

• OS: Platform-independent (Linux / Windows supported)

• Note: External software will be installed in /opt directory

Step 1: Launch EC2 & Connect

• Launch an Amazon EC2 instance (Redhat)

• SSH into the instance:

Step 2: Switch to Root User

sudo su -

Step 3: Install Java (JDK)

Java is required before installing Maven, because Maven runs on Java.

1.Update system packages (updates all installed software):

yum update -y

2. Install JDK 21

yum install java-21-openjdk-devel -y

3. Verify Java Installation

java --version

Step 4: Install Maven

Make sure Java is installed before this step.

1. Install tools to download and extract Maven:

yum install wget unzip -y

2. Download & Extract Maven

• It is a good practice to install external tools like Maven in the /opt directory

• Download Maven from the official Apache website:

• Always use the official source: https://maven.apache.org/download.cgi

cd /opt
wget https://dlcdn.apache.org/maven/maven-3/3.9.10/binaries/apache-maven-3.9.10-bin.zip

• Unzip the Downloaded File

• After the download, you will see the file: apache-maven-3.9.10-bin.zip. Unzip that file.

unzip apache-maven-3.9.10-bin.zip

• After extraction, a new directory will be created:

Why mvn -v Might Not Work After Installation

• Even after successful extraction, if you try: mvn --version

• You might get: mvn: command not found

• Reason: Because the mvn executable is not yet part of your system’s PATH, the terminal doesn’t know where to find it.

Step 5. Set Environment Variables

Open .bash_profile:

vi ~/.bash_profile

Add the following lines at the end:

export M2_HOME=/opt/apache-maven-3.9.10
export PATH=$PATH:$M2_HOME/bin

• export M2_HOME=/opt/apache-maven-3.9.10
  → This line tells the system where Maven is installed. Some tools and scripts use this variable to locate Maven automatically.

• export PATH=$PATH:$M2_HOME/bin
  → This line updates the system PATH so that you can run the mvn command from anywhere in the terminal, without typing the full path like /opt/apache-maven-3.9.10/bin/mvn.

Save and exit.

Step 6. Reload .bash_profile

This loads your changes into the current terminal session, next Verify Maven Installation

source ~/.bash_profile
mvn --version
# or
mvn -v

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4.Maven Directory Structure (After Installation)

When you extract Maven, you'll see a folder like this:

apache-maven-<version>/
├── bin/
├── boot/
├── lib/
├── conf/

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bin/ — Executable Scripts

• Contains executable files like mvn (Linux) or mvn.cmd (Windows)

• This is how you run Maven commands from terminal

boot/ — Startup Libraries

• Contains internal libraries used to bootstrap Maven.

• Example: plexus-classworlds-*.jar — helps load Maven core classes.

• These are essential for Maven to start correctly.

lib/ — Maven Core Libraries

• Contains all the essential .jar files Maven needs to run.

• Example files:

  • maven-core.jar

  • maven-model.jar

  • maven-plugin-api.jar

• These libraries define how Maven works internally.

conf/ — Configuration Directory

• Contains global configuration files for Maven.

• Most important file: settings.xml

This is the most important file inside the conf/ directory.

What Can You Configure in settings.xml?

1. Proxies

• Use case: If your system is behind a firewall (e.g., corporate network) and you need Maven to access the internet.

• You can define proxy host, port, username, and password.

2. Remote Repositories

• These are external repositories from where Maven downloads dependencies or uploads your own artifacts.

• Examples: Nexus ,JFrog Artifactory

• You can configure the repository URL and credentials.

3. Server Authentication (Credentials)

• You can securely store login credentials in settings.xml for:

• Nexus (for publishing your .jar, .war, .ear files)

• SonarQube (for uploading code quality reports)