Maven

🔧 What is Maven?

Apache Maven is a build automation and project management tool for Java projects. It simplifies dependency management, project structure, and build processes through standardized conventions and declarative configuration using XML.


<!-- Basic Maven project structure -->
<project>
    <groupId>com.example</groupId>
    <artifactId>my-app</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>
</project>

Maven Features

📦

Dependency Management

Automatic library download and management

<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.13.2</version>
</dependency>

🏗️

Build Lifecycle

Standardized build phases

mvn clean compile test package

📁

Project Structure

Standard directory layout

src/main/java
src/main/resources
src/test/java

🔌

Plugins

Extensible build functionality

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
</plugin>

🔹 Basic Maven Project Structure

Maven follows a standard directory layout:

my-app/
├── pom.xml
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/App.java
│   │   └── resources/
│   │       └── application.properties
│   └── test/
│       ├── java/
│       │   └── com/example/AppTest.java
│       └── resources/
└── target/
    ├── classes/
    └── my-app-1.0.0.jar

Directory Purpose:

src/main/java - Source code

src/test/java - Test code

target/ - Compiled output

🔹 Complete pom.xml Example

A comprehensive Maven project configuration:

<?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 -->
    <groupId>com.example</groupId>
    <artifactId>my-web-app</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>
    
    <name>My Web Application</name>
    <description>A sample Spring Boot application</description>
    
    <!-- Properties -->
    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <spring.boot.version>3.2.0</spring.boot.version>
        <junit.version>5.9.2</junit.version>
    </properties>
    
    <!-- Dependencies -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>${spring.boot.version}</version>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <version>${spring.boot.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    
    <!-- Build configuration -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring.boot.version}</version>
            </plugin>
        </plugins>
    </build>
</project>

🔹 Maven Commands

Essential Maven commands for daily development:

# Clean previous builds
mvn clean

# Compile source code
mvn compile

# Run tests
mvn test

# Package into JAR/WAR
mvn package

# Install to local repository
mvn install

# Deploy to remote repository
mvn deploy

# Run Spring Boot application
mvn spring-boot:run

# Generate project from archetype
mvn archetype:generate -DgroupId=com.example \
    -DartifactId=my-app \
    -DarchetypeArtifactId=maven-archetype-quickstart \
    -DinteractiveMode=false

Build Lifecycle:

validate → compile → test → package → install → deploy

🔹 Dependency Scopes

Different dependency scopes in Maven:

<dependencies>
    <!-- Compile scope (default) - available in all phases -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>6.0.0</version>
        <scope>compile</scope>
    </dependency>
    
    <!-- Test scope - only for testing -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13.2</version>
        <scope>test</scope>
    </dependency>
    
    <!-- Runtime scope - not needed for compilation -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.33</version>
        <scope>runtime</scope>
    </dependency>
    
    <!-- Provided scope - provided by container -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

🔹 Maven Profiles

Use profiles for different environments:

<profiles>
    <profile>
        <id>development</id>
        <activation>
            <activeByDefault>true</activeByDefault>
        </activation>
        <properties>
            <database.url>jdbc:h2:mem:devdb</database.url>
            <log.level>DEBUG</log.level>
        </properties>
    </profile>
    
    <profile>
        <id>production</id>
        <properties>
            <database.url>jdbc:mysql://prod-server:3306/mydb</database.url>
            <log.level>WARN</log.level>
        </properties>
        <dependencies>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.33</version>
            </dependency>
        </dependencies>
    </profile>
</profiles>

<!-- Activate profile: mvn clean package -Pproduction -->