What is Maven?

What is Maven?

Think of Maven like a smart project assistant:

• Without Maven: Manually download JARs, manage versions, write build scripts
• With Maven: Declare what you need, Maven handles the rest

Why Use Maven?

Installing Maven

# Check if Maven is installed
mvn --version

# Output:
# Apache Maven 3.9.6
# Java version: 21.0.1
# OS name: "windows 10"

# Installation options:
# 1. Download from https://maven.apache.org/download.cgi
# 2. Use package manager:
#    - Windows: choco install maven
#    - Mac: brew install maven
#    - Linux: apt install maven
# 3. Most IDEs include Maven (IntelliJ, Eclipse)

Standard Project Structure

my-project/
├── pom.xml                          # Project configuration (THE key file)
├── src/
│   ├── main/
│   │   ├── java/                    # Java source code
│   │   │   └── com/example/
│   │   │       └── App.java
│   │   └── resources/               # Configuration files, properties
│   │       └── application.properties
│   └── test/
│       ├── java/                    # Test source code
│       │   └── com/example/
│       │       └── AppTest.java
│       └── resources/               # Test resources
└── target/                          # Build output (generated)
    ├── classes/                     # Compiled classes
    ├── test-classes/                # Compiled test classes
    └── my-project-1.0.0.jar         # Final artifact

Basic pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
         http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <!-- Project coordinates (unique identifier) -->
    <groupId>com.example</groupId>       <!-- Organization/company -->
    <artifactId>my-app</artifactId>     <!-- Project name -->
    <version>1.0.0</version>           <!-- Version -->
    <packaging>jar</packaging>         <!-- Output type: jar, war, pom -->

    <!-- Project metadata -->
    <name>My Application</name>
    <description>A sample Maven project</description>

    <!-- Properties (variables) -->
    <properties>
        <java.version>21</java.version>
        <maven.compiler.source>${java.version}</maven.compiler.source>
        <maven.compiler.target>${java.version}</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <!-- Dependencies (libraries your project needs) -->
    <dependencies>
        <!-- Example: JUnit for testing -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>5.10.0</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

Common Maven Commands

# Clean - removes target directory
mvn clean

# Compile - compiles source code
mvn compile

# Test - runs unit tests
mvn test

# Package - creates JAR/WAR file
mvn package

# Install - installs to local repository (~/.m2/repository)
mvn install

# Combined commands (most common)
mvn clean install          # Clean, compile, test, package, install
mvn clean package          # Clean, compile, test, package
mvn clean test             # Clean, compile, test

# Skip tests (use sparingly!)
mvn package -DskipTests

# Run with specific profile
mvn package -Pprod

# Show dependency tree
mvn dependency:tree

# Check for dependency updates
mvn versions:display-dependency-updates

Maven Repositories

// How Maven finds dependencies:

// 1. Local Repository (your machine)
//    ~/.m2/repository/
//    - Caches downloaded dependencies
//    - Stores your installed projects

// 2. Central Repository (default remote)
//    https://repo.maven.apache.org/maven2/
//    - Hosts millions of open source libraries
//    - Automatically searched if not in local

// 3. Custom/Private Repositories
//    - Company internal repositories
//    - Configured in pom.xml or settings.xml

Adding Custom Repository

<repositories>
    <repository>
        <id>company-repo</id>
        <url>https://nexus.company.com/repository/maven-public/</url>
    </repository>
</repositories>

Creating a New Maven Project

# Using archetype (project template)
mvn archetype:generate \
    -DgroupId=com.example \
    -DartifactId=my-app \
    -DarchetypeArtifactId=maven-archetype-quickstart \
    -DinteractiveMode=false

# Common archetypes:
# maven-archetype-quickstart  - Simple Java project
# maven-archetype-webapp      - Web application (WAR)

# Or use Spring Initializr for Spring Boot projects:
# https://start.spring.io

Maven vs Other Build Tools

Best Practices

Summary