POM File

About

In Maven, the Project Object Model (pom.xml) is the heart of our build system. It defines what our project is, how it should be built, what it depends on, and how it interacts with the Maven ecosystem.

While small projects may use a minimal pom.xml, larger and enterprise projects often have highly structured POMs that handle:

• Dependency management

• Build configuration

• Multi-module orchestration

• Profiles for environment-specific builds

Understanding its structure means understanding how Maven thinks about projects and that’s the first step toward mastering Maven.

Sample POM File

<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 
                             https://maven.apache.org/xsd/maven-4.0.0.xsd">

    <!-- ===== Model Version ===== -->
    <modelVersion>4.0.0</modelVersion>

    <!-- ===== Project Coordinates ===== -->
    <groupId>com.example</groupId>
    <artifactId>sample-app</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <!-- ===== Project Metadata ===== -->
    <name>Sample Maven Application</name>
    <description>An example project demonstrating all POM sections</description>
    <url>https://example.com/sample-app</url>

    <!-- ===== Parent POM ===== -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.1</version>
        <relativePath/> <!-- Look up parent from repository -->
    </parent>

    <!-- ===== Properties ===== -->
    <properties>
        <java.version>17</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>
        <maven.build.timestamp.format>yyyy-MM-dd HH:mm:ss</maven.build.timestamp.format>
    </properties>

    <!-- ===== Dependency Management ===== -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-databind</artifactId>
                <version>2.15.0</version>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <!-- ===== Dependencies ===== -->
    <dependencies>
        <!-- Spring Boot Web -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- Lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <!-- Testing -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <!-- ===== Build Configuration ===== -->
    <build>
        <finalName>${project.artifactId}-${project.version}</finalName>
        <sourceDirectory>src/main/java</sourceDirectory>
        <testSourceDirectory>src/test/java</testSourceDirectory>

        <!-- Plugins -->
        <plugins>
            <!-- Compiler Plugin -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.11.0</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>

            <!-- Surefire Plugin (Unit Testing) -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>3.1.2</version>
                <configuration>
                    <skipTests>false</skipTests>
                </configuration>
            </plugin>

            <!-- JAR Plugin (Custom Manifest) -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.3.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>com.example.MainApplication</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <!-- ===== Repositories ===== -->
    <repositories>
        <repository>
            <id>central</id>
            <name>Maven Central Repository</name>
            <url>https://repo1.maven.org/maven2/</url>
        </repository>
    </repositories>

    <!-- ===== Plugin Repositories ===== -->
    <pluginRepositories>
        <pluginRepository>
            <id>central</id>
            <name>Maven Central Plugins</name>
            <url>https://repo1.maven.org/maven2/</url>
        </pluginRepository>
    </pluginRepositories>

    <!-- ===== Profiles ===== -->
    <profiles>
        <!-- Development Profile -->
        <profile>
            <id>dev</id>
            <activation>
                <activeByDefault>true</activeByDefault>
            </activation>
            <properties>
                <maven.compiler.debug>true</maven.compiler.debug>
            </properties>
        </profile>

        <!-- Production Profile -->
        <profile>
            <id>prod</id>
            <properties>
                <maven.compiler.debug>false</maven.compiler.debug>
            </properties>
        </profile>
    </profiles>

    <!-- ===== Modules (Multi-module projects) ===== -->
    <modules>
        <module>service-module</module>
        <module>web-module</module>
    </modules>

</project>

The <project> Root Element

In Maven, every POM must start with a <project> element. This is the container for all other POM elements - think of it as the root of the Maven configuration tree.

From our sample file:

<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 
                             https://maven.apache.org/xsd/maven-4.0.0.xsd">

A. The xmlns Attribute

xmlns="http://maven.apache.org/POM/4.0.0"

• Defines the default XML namespace for Maven’s POM schema.

• Ensures Maven interprets elements like <groupId> and <version> according to POM 4.0.0 rules.

• Without this, Maven could throw parsing errors or misinterpret elements.

B. The xmlns:xsi Attribute

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

• This namespace is not Maven-specific — it’s an XML Schema Instance namespace from W3C.

• It enables the use of xsi:schemaLocation in XML files to tell tools where to find the schema definition.

C. The xsi:schemaLocation Attribute

xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
                    https://maven.apache.org/xsd/maven-4.0.0.xsd"

• Maps the Maven namespace to the actual XSD file that describes POM structure.

• The first part: http://maven.apache.org/POM/4.0.0 — the namespace URI.

• The second part: https://maven.apache.org/xsd/maven-4.0.0.xsd — the location of the XML Schema Definition (XSD) for Maven POM.

When tools like IntelliJ or Eclipse read our pom.xml, they use this schema to:

• Validate if elements are correct

• Show autocomplete suggestions

• Catch typos or misplaced elements before build time

D. Closing the <project> Tag

After defining namespaces, the <project> tag is not closed immediately instead, it wraps all other POM sections until the very end:

</project>

E. Why This Section Matters ?

• Without a proper <project> root with namespaces, Maven won’t recognize our file as a valid POM.

• Proper namespace/schema definitions ensure:

  • IDE support (syntax highlighting, code completion)

  • Validation before build

  • Compatibility with Maven 3.x and above

The <modelVersion> Element

From our sample:

<modelVersion>4.0.0</modelVersion>

A. Purpose

• Defines which version of the Project Object Model (POM) we are using.

• Ensures Maven knows how to interpret the structure and available elements in our POM.

B. Current Value

• Always 4.0.0 for Maven 2, Maven 3, and Maven 4 (as of now).

• This version number hasn’t changed for years because:

  • The POM structure has remained stable.

  • Backward compatibility is a core principle in Maven.

C. Historical Context

• Maven 1.x had a different POM format (no <modelVersion> at all).

• When Maven 2 was released, they introduced POM v4.0.0 to unify how build configuration was defined.

• Future changes (if Maven 5 introduces POM v5.0.0) would require updating this field.

D. What Happens if We Change It ?

• If we set it to something unsupported, Maven will throw:

  Non-parseable POM

• This is one of the very few non-optional POM elements.

E. Best Practice

• Keep it as the very first child of <project>.

• Always use:

  <modelVersion>4.0.0</modelVersion>

• Don’t remove it, even though Maven might sometimes seem to work without it in IDE-generated POMs.

Project Coordinates

From our sample POM:

<groupId>com.example</groupId>
<artifactId>sample-app</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>jar</packaging>

These four elements tell Maven:

• What our project is called

• Who owns it

• Which version is being built

• What type of artifact is produced

They are collectively known as GAV (GroupId, ArtifactId, Version) + Packaging.

A. <groupId>

• Defines the organization or group that produces the project.

• Usually follows reverse domain naming:

  • Example: com.google.guava

  • For internal projects: com.companyname.project

• It ensures global uniqueness in repositories.

Why reverse domain ?

• Domains are unique to an organization, so reversing them avoids clashes.

• Example: com.example → no other company will accidentally use our namespace.

B. <artifactId>

• The name of the built artifact (without version or extension).

• Together with groupId, it must be unique.

• Examples:

  • spring-core

  • hibernate-entitymanager

  • sample-app

• When packaged, Maven appends:

  <artifactId>-<version>.<packaging>

  Example:

  sample-app-1.0.0-SNAPSHOT.jar

C. <version>

• The current version of the project.

• Formats:

  • Release: 1.0.0, 2.1.5

  • Snapshot: 1.0.0-SNAPSHOT

• Snapshot means:

  • Work in progress

  • Can change without notice

  • Maven won’t cache aggressively — it checks for updates on each build

• Release means:

  • Immutable

  • Stored permanently in repository without overwriting

Always use SNAPSHOT during development, and set a proper release version before publishing.

D. <packaging>

• Defines the type of artifact Maven should create.

• Common values:

  • jar — Java library

  • war — Web application

  • pom — Parent or aggregator POM

  • ear — Enterprise Archive

  • rar — Resource Adapter Archive

• If omitted, defaults to jar.

E. How Maven Uses GAV ?

Maven stores artifacts in the repository structure:

~/.m2/repository/<groupId path>/<artifactId>/<version>/<artifactId>-<version>.<packaging>

Example for our sample:

~/.m2/repository/com/example/sample-app/1.0.0-SNAPSHOT/sample-app-1.0.0-SNAPSHOT.jar

F. Best Practices

1. Uniqueness: Ensure groupId + artifactId combination is unique across all repositories we publish to.

2. Semantic Versioning: Use MAJOR.MINOR.PATCH format for versions.

3. Packaging Consistency: Keep packaging type aligned with project type (don’t package a web app as jar unless using Spring Boot’s embedded server).

Project Metadata

From our sample:

<name>Sample Maven Application</name>
<description>An example project demonstrating all POM sections</description>
<url>https://example.com/sample-app</url>

A. <name>

• A readable project name — not necessarily the same as artifactId.

• Appears in:

  • Generated project documentation (mvn site)

  • IDE displays

  • Maven Central listings

• Example:

  <name>Apache Commons IO</name>

  vs.

  <artifactId>commons-io</artifactId>

B. <description>

• A one- or two-line summary of our project’s purpose.

• Visible in generated Maven reports, repository browsers, and artifact search tools.

• Should be:

  • Clear — avoid jargon unless our audience knows it

  • Concise — a few sentences at most

• Example:

  <description>A utility library for working with IO in Java</description>

C. <url>

• The official homepage or documentation URL for the project.

• Can point to:

  • Project website

  • GitHub repository

  • Internal wiki (for private projects)

• Example:

  <url>https://github.com/apache/commons-io</url>

D. Why Metadata Matters ?

1. Discoverability — if someone finds our artifact on Maven Central, they should immediately know what it does and where to learn more.

2. Documentation Integration — Maven site plugins and reporting tools pull these values automatically.

3. Team Communication — in large organizations, metadata helps new developers quickly grasp project purpose.

E. Best Practices

• Always include <name> and <description> even in private/internal projects - future maintainers will thank us.

• Keep <url> up to date. Nothing says “abandoned” like a broken homepage link.

• Treat this like a business card for our artifact.

The <parent> Section

From our sample:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.1.1</version>
    <relativePath/> <!-- Look up parent from repository -->
</parent>

A. Purpose

The <parent> element allows our project to inherit:

• Dependency versions

• Plugin configurations

• Properties

• Build settings

Instead of redefining them in every project, we can define them once in a parent POM and let child POMs inherit them.

B. Structure

1. <groupId> The parent project’s group ID.

2. <artifactId> The parent project’s artifact ID.

3. <version> The parent POM’s version we want to use.

4. <relativePath> (optional)

   • If the parent POM is in our local filesystem (multi-module build), Maven uses this path to locate it.

   • Default: ../pom.xml

   • Setting it to empty (<relativePath/>) forces Maven to look in the repository instead.

C. How Inheritance Works ?

• If the child POM omits certain elements (like <properties>, <dependencyManagement>, <build>), Maven will merge them from the parent POM.

• If the child redefines an element, it overrides the parent’s value.

• We can even have multi-level inheritance (parent → grandparent POM).

D. Real-World Examples

• Spring Boot uses spring-boot-starter-parent to:

  • Predefine common dependency versions (BOM style)

  • Configure compiler & test plugins

  • Set default encoding, resource filtering, etc.

• Large organizations create internal parent POMs to enforce:

  • Coding standards (plugin rules)

  • Common logging frameworks

  • Unified dependency versions

E. Inheritance vs. Aggregation

• Inheritance (<parent>) — share configuration; child still builds independently.

• Aggregation (<modules>) — build multiple modules in one go; no automatic config sharing unless they also share a parent.

F. Best Practices

• If using a parent from a public framework (like Spring Boot), always match versions carefully with the framework we are using.

• For internal projects, create a custom parent POM for consistency across all microservices/libraries.

• Avoid deep inheritance chains — they make troubleshooting difficult.

The <properties> Section

From our sample:

<properties>
    <java.version>17</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>
    <maven.build.timestamp.format>yyyy-MM-dd HH:mm:ss</maven.build.timestamp.format>
</properties>

A. Purpose

• Defines custom variables that can be reused throughout the POM.

• Makes the configuration more maintainable and less repetitive.

• Allows for centralized updates — change one property, and it updates everywhere it’s used.

B. How Properties Work ?

• We reference a property with ${propertyName}.

• Maven interpolates (replaces) these placeholders before executing the build.

• Properties can:

  • Be custom-defined in <properties>

  • Come from Maven itself (built-in)

  • Be passed via CLI (mvn clean install -Dproperty=value)

C. Common Use Cases

1. Java version settings

   <java.version>17</java.version>

   Used by compiler and other plugins.

2. Encoding

   <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

3. Timestamp formatting

   <maven.build.timestamp.format>yyyy-MM-dd HH:mm:ss</maven.build.timestamp.format>

4. Plugin or dependency versions

   <spring.boot.version>3.1.1</spring.boot.version>

   Then:

   <version>${spring.boot.version}</version>

D. Built-In Maven Properties

Maven comes with predefined variables we can use without declaring them:

• ${basedir} — root directory of the project

• ${project.version} — version from <version> tag

• ${project.build.directory} — usually target

• ${settings.localRepository} — path to local repo (~/.m2/repository)

• ${java.home} — path to Java installation

E. CLI-Defined Properties

We can override or add properties at runtime:

mvn clean package -Djava.version=21

This will temporarily set ${java.version} to 21 for that build.

F. Best Practices

1. Centralize versions in <properties> — avoids “version drift” in dependencies/plugins.

2. Use meaningful names for custom properties — avoid overly generic names like <version>.

3. Don’t hardcode Java or encoding values in multiple places — use a single property reference.

4. Be cautious with overriding properties via CLI in CI/CD — it can cause inconsistent builds if not documented.

The <dependencyManagement> Section

From our sample:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>3.1.1</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.28</version>
        </dependency>
    </dependencies>
</dependencyManagement>

A. Purpose

• Acts like a version control center for dependencies.

• Lets us declare versions once and reuse them across multiple modules without repeating the version each time.

• Especially useful in multi-module projects.

B. How It Works ?

• Dependencies inside <dependencyManagement> are not automatically included in the build.

• They only define defaults for:

  • version

  • scope

  • exclusions

• To actually use them, we still declare them in <dependencies> — but without the version.

Example:

<!-- In parent POM -->
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>3.1.1</version>
        </dependency>
    </dependencies>
</dependencyManagement>

<!-- In child POM -->
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <!-- No version needed -->
    </dependency>
</dependencies>

Maven will automatically inject 3.1.1 from the parent.

C. Benefits

1. Consistency — no accidental version mismatches between modules.

2. Centralized updates — bump a version in one place, all modules get it.

3. Cleaner child POMs — less duplication, more readable.

D. Typical Uses

• Multi-module projects — Parent POM defines versions, child POMs just declare dependencies without versions.

• BOM (Bill of Materials) imports — Import another project’s dependency versions (e.g., Spring Boot’s BOM).

Example of BOM import:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>3.1.1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

This imports all managed versions from Spring Boot’s BOM.

E. Best Practices

• Keep <dependencyManagement> only in parent POMs — avoid in regular modules unless they’re BOMs themselves.

• Avoid mixing managed and unmanaged versions for the same dependency — it creates confusion.

• Prefer BOM imports for large frameworks instead of manually listing every dependency.

The <dependencies> Section

From our sample:

<dependencies>
    <!-- Web framework -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- Lombok for boilerplate code reduction -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <scope>provided</scope>
    </dependency>

    <!-- Testing library -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

A. Purpose

• Lists all the external and internal libraries our project depends on.

• Maven automatically:

  • Downloads them from repositories.

  • Adds them to the classpath.

  • Handles transitive dependencies (dependencies of our dependencies).

B. Key Elements

Each <dependency> typically has:

1. <groupId> — Organization or project namespace.

2. <artifactId> — Unique name of the library/module.

3. <version> — The specific release we want.

   • Optional if managed in <dependencyManagement> or imported BOM.

4. <scope> — Defines where the dependency is available (more on this below).

5. <optional> (optional) — If true, not included transitively by projects that depend on us.

6. <exclusions> (optional) — Used to block unwanted transitive dependencies.

C. Dependency Scopes

Scope	Available In	Typical Use Case
compile (default)	All phases (compile, test, runtime)	Core libraries our app always needs
provided	Compile + test, not runtime	Servlet API (container provides it)
runtime	Test + runtime, not compile	JDBC driver
test	Only in test classpath	JUnit, Mockito
system	Like provided, but requires explicit local path	Rarely used, for local JARs
import	Only in <dependencyManagement>	For BOM imports

D. Transitive Dependencies

If our dependency depends on something else, Maven pulls it in automatically. Example:

• We add spring-boot-starter-web

• Maven fetches:

  • Spring MVC

  • Jackson

  • Tomcat

  • And so on...

We can exclude unwanted transitive dependencies:

<dependency>
    <groupId>com.example</groupId>
    <artifactId>library</artifactId>
    <exclusions>
        <exclusion>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

E. Best Practices

• Use BOM + <dependencyManagement> to avoid repeating versions.

• Be careful with scope=provided — using it incorrectly can cause runtime ClassNotFoundException.

• Regularly check for unused dependencies (mvn dependency:analyze).

The <build> Section

From our sample:

<build>
    <finalName>my-app</finalName>

    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.11.0</version>
            <configuration>
                <source>${java.version}</source>
                <target>${java.version}</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.3.0</version>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <mainClass>com.example.MainApp</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

A. Purpose

• Defines how Maven builds our project:

  • Output naming

  • Plugins to run

  • Compiler and packaging settings

  • Directory configurations

B. Key Elements

1. <finalName>

• Sets the name of the generated artifact without extension.

• Example:

  • finalName = my-app

  • Packaging = jar

  • Output file = my-app.jar

2. <plugins>

• Plugins are Maven’s workhorses — they handle compilation, packaging, testing, deployment, etc.

• Inside each <plugin>:

  • <groupId> — Usually org.apache.maven.plugins for official plugins.

  • <artifactId> — Plugin name (e.g., maven-compiler-plugin).

  • <version> — Specific plugin version.

  • <configuration> — Custom settings for that plugin.

C. Commonly Used Plugins

1. Compiler Plugin

   <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-compiler-plugin</artifactId>
       <version>3.11.0</version>
       <configuration>
           <source>${java.version}</source>
           <target>${java.version}</target>
       </configuration>
   </plugin>

   • Controls Java source/target version.

2. JAR Plugin

   <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-jar-plugin</artifactId>
       <version>3.3.0</version>
       <configuration>
           <archive>
               <manifest>
                   <addClasspath>true</addClasspath>
                   <mainClass>com.example.MainApp</mainClass>
               </manifest>
           </archive>
       </configuration>
   </plugin>

   • Configures how JAR files are packaged and adds metadata.

3. Surefire Plugin (for tests)

   <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-surefire-plugin</artifactId>
       <version>3.1.2</version>
   </plugin>

D. Advanced Build Customization

The <build> section can also include:

• <resources> — Non-Java files to include in build.

• <testResources> — Test-specific resources.

• <directory> — Change the default output dir (default: target).

• <filters> — Filter resources with property substitution.

Example:

<resources>
    <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
    </resource>
</resources>

E. Best Practices

• Always pin plugin versions — Maven defaults can change unexpectedly.

• Group related plugin configs together for readability.

• Avoid overloading pom.xml with complex plugin logic — use external config files if necessary.

• Keep <finalName> meaningful for CI/CD pipelines.

The <profiles> Section

From our sample:

<profiles>
    <profile>
        <id>dev</id>
        <properties>
            <env>development</env>
        </properties>
        <activation>
            <activeByDefault>true</activeByDefault>
        </activation>
        <dependencies>
            <dependency>
                <groupId>org.hsqldb</groupId>
                <artifactId>hsqldb</artifactId>
                <version>2.7.1</version>
                <scope>runtime</scope>
            </dependency>
        </dependencies>
    </profile>

    <profile>
        <id>prod</id>
        <properties>
            <env>production</env>
        </properties>
        <dependencies>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>8.0.32</version>
                <scope>runtime</scope>
            </dependency>
        </dependencies>
    </profile>
</profiles>

A. Purpose

• Profiles let us change Maven’s behavior based on conditions.

• We can define:

  • Different dependencies

  • Different build plugins

  • Different properties

  • Different resource directories

• Useful for dev vs test vs prod builds, or platform-specific settings.

B. Key Elements

1. <id>

• Unique profile name.

• Activated with:

  mvn clean install -Pprod

2. <activation>

• Defines conditions for automatic activation:

  • <activeByDefault> — Always active unless another profile is explicitly chosen.

  • <jdk> — Activates based on JDK version.

  • <os> — Activates based on OS name, family, arch, version.

  • <property> — Activates if a system property is present.

  • <file> — Activates if a file exists (or not).

Example:

<activation>
    <property>
        <name>env</name>
        <value>production</value>
    </property>
</activation>

3. Profile-specific sections

• <dependencies> — Add dependencies only for that profile.

• <build> — Override or add build settings for that profile.

• <properties> — Define environment-specific variables.

C. How Profiles Work

• Without profiles — All settings apply to all builds.

• With profiles — Only active profiles’ settings merge into the final build configuration.

Maven merges:

1. Global settings (in settings.xml)

2. Active profile settings (from pom.xml or settings.xml)

3. Command-line arguments

D. Typical Use Cases

• Switching database drivers between dev (HSQLDB) and prod (MySQL).

• Enabling/disabling debug logging.

• Using different Java versions for builds.

• Packaging different resource sets.

E. Best Practices

• Use profiles for environmental differences, not for optional features in the same environment.

• Avoid too many profiles - it can make builds unpredictable.

• Always document profile purposes for other developers.

The <repositories> Section

Example:

<repositories>
    <repository>
        <id>central</id>
        <url>https://repo.maven.apache.org/maven2</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>

    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>true</enabled>
        </snapshots>
    </repository>
</repositories>

A. Purpose

• Defines where Maven should look for dependencies besides the default Maven Central repository.

• Useful when:

  • Using internal corporate artifact repositories (like Nexus or Artifactory)

  • Using third-party repositories (e.g., JitPack, Spring Milestone)

  • Accessing snapshot versions not in Maven Central

B. Key Elements

1. <id>

• Unique identifier for the repository.

• Used in logs, dependency resolution, and possible plugin configs.

2. <url>

• Repository base URL.

• Must point to a valid Maven repository structure.

3. <releases> and <snapshots>

• Control whether the repo is used for release artifacts, snapshot artifacts, or both.

• <enabled> can be true or false.

Example:

<releases>
    <enabled>true</enabled>
</releases>
<snapshots>
    <enabled>false</enabled>
</snapshots>

4. Authentication

• For private repos, credentials are stored in settings.xml, not the pom.xml.

• Example in settings.xml:

<servers>
    <server>
        <id>internal-repo</id>
        <username>myuser</username>
        <password>mypassword</password>
    </server>
</servers>

• The <id> here must match the <id> in <repository>.

C. How Maven Resolves Dependencies

1. Local Repository — Checks ~/.m2/repository first.

2. Remote Repositories — Checks in order defined in <repositories>.

3. Mirror Settings — Can redirect all requests via settings.xml.

D. Best Practices

• Do not overuse external repositories — it can slow builds and create dependency conflicts.

• Always pin dependencies to specific versions when using non-central repos.

• Use mirrors in settings.xml for centralizing access to multiple repositories.

• For corporate projects, prefer a single internal proxy to external repositories.

The <pluginRepositories> Section

Example:

<pluginRepositories>
    <pluginRepository>
        <id>apache-plugins</id>
        <url>https://repo.maven.apache.org/maven2</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </pluginRepository>

    <pluginRepository>
        <id>custom-plugin-repo</id>
        <url>https://plugins.example.com/maven2</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>true</enabled>
        </snapshots>
    </pluginRepository>
</pluginRepositories>

A. Purpose

• Specifies where Maven should look for build plugins other than the default Maven Central repository.

• Maven uses separate repository lists for plugins and dependencies.

• Needed if:

  • We are using a plugin not hosted on Maven Central

  • Our organization hosts custom build plugins internally

B. Key Elements

1. <pluginRepository>

• Similar structure to <repository>:

  • <id> — Unique name

  • <url> — Repository location

  • <releases> / <snapshots> — Enable/disable artifact types

2. Authentication

• Just like normal repositories, credentials go into settings.xml:

<servers>
    <server>
        <id>custom-plugin-repo</id>
        <username>builduser</username>
        <password>secret</password>
    </server>
</servers>

3. Mirrors

• We can redirect all plugin repo lookups through a mirror in settings.xml.

C. Difference from <repositories>

For Dependencies	For Plugins
<repositories>	<pluginRepositories>
Controls where Maven searches for JARs, libraries, artifacts	Controls where Maven searches for build plugins
Used during dependency resolution	Used when fetching plugins for build lifecycle phases

D. Best Practices

• Avoid mixing dependency repositories with plugin repositories unless necessary.

• Keep custom plugins documented without a central repo, future builds may fail.

• For corporate environments, use an internal mirror/proxy to cache plugin artifacts.

The <distributionManagement> Section

Example:

<distributionManagement>
    <repository>
        <id>releases-repo</id>
        <name>Company Releases</name>
        <url>https://repo.company.com/maven2/releases</url>
    </repository>

    <snapshotRepository>
        <id>snapshots-repo</id>
        <name>Company Snapshots</name>
        <url>https://repo.company.com/maven2/snapshots</url>
    </snapshotRepository>

    <site>
        <id>project-site</id>
        <name>Project Documentation</name>
        <url>scp://docs.company.com/www/project</url>
    </site>

    <downloadUrl>https://downloads.company.com/project</downloadUrl>
</distributionManagement>

A. Purpose

• Tells Maven where to deploy built artifacts (JAR, WAR, POM, etc.).

• Defines separate locations for:

  • Release artifacts (stable versions)

  • Snapshot artifacts (in-progress versions)

  • Generated project site (HTML documentation)

• Works together with mvn deploy phase.

B. Key Elements

1. <repository>

• Destination for release versions.

• Only accepts non-SNAPSHOT version numbers.

• Example:

<repository>
    <id>releases-repo</id>
    <url>https://repo.company.com/maven2/releases</url>
</repository>

2. <snapshotRepository>

• Destination for SNAPSHOT versions.

• SNAPSHOT builds allow overwriting — they are not immutable.

3. <site>

• Where Maven publishes the site documentation (mvn site:deploy).

4. <downloadUrl>

• Optional — URL for users to manually download artifacts outside Maven.

C. Authentication

• Credentials must not be stored in pom.xml — put them in settings.xml:

<servers>
    <server>
        <id>releases-repo</id>
        <username>deployuser</username>
        <password>deploypass</password>
    </server>
</servers>

• The <id> here matches the <id> in <distributionManagement>.

D. How It Works ?

1. We run:

   mvn clean deploy

2. Maven:

   • Builds our project

   • Creates the POM and packaged artifact

   • Pushes it to the release or snapshot repo based on the version

E. Best Practices

• Always separate release and snapshot repositories.

• Keep deployment credentials outside of source control.

• Automate deployment in CI/CD pipelines to prevent manual errors.

• Avoid deploying directly to public repos without review.

The <reporting> Section

Example:

<reporting>
    <outputDirectory>${project.build.directory}/site</outputDirectory>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-project-info-reports-plugin</artifactId>
            <version>3.4.5</version>
            <reportSets>
                <reportSet>
                    <reports>
                        <report>dependencies</report>
                        <report>plugins</report>
                        <report>licenses</report>
                    </reports>
                </reportSet>
            </reportSets>
        </plugin>

        <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.8.10</version>
            <reportSets>
                <reportSet>
                    <reports>
                        <report>report</report>
                    </reports>
                </reportSet>
            </reportSets>
        </plugin>
    </plugins>
</reporting>

A. Purpose

• Controls Maven’s site reporting system.

• Defines which reports are generated when we run:

  mvn site

• These reports are often published to a website or artifact repository for:

  • Project documentation

  • Code quality analysis

  • Dependency tracking

B. Key Elements

1. <outputDirectory>

• Where the generated site is stored locally (default: ${project.build.directory}/site).

2. <plugins>

• List of reporting plugins.

• Important: This <plugins> inside <reporting> is different from the one inside <build> — it’s used only for generating reports, not building the project.

3. <reportSets>

• Defines specific sets of reports a plugin should generate.

• Allows filtering which reports run for different situations.

C. Common Reporting Plugins

1. maven-project-info-reports-plugin

   • Generates project info: dependencies, plugins, licenses, SCM, etc.

2. maven-javadoc-plugin

   • Generates JavaDocs for our codebase.

3. jacoco-maven-plugin

   • Generates code coverage reports.

4. maven-surefire-report-plugin

   • Creates test result reports.

D. Best Practices

• Don’t overload <reporting> with unnecessary plugins — large report sets slow down site generation.

• Use it in combination with CI/CD pipelines to publish reports automatically.

• Keep plugin versions pinned to avoid sudden output changes.

Project Metadata Sections

These elements don’t directly affect compilation or packaging, but they are critical for documentation, open-source compliance, and automated tooling.

A. <licenses>

Example:

<licenses>
    <license>
        <name>Apache License, Version 2.0</name>
        <url>https://www.apache.org/licenses/LICENSE-2.0</url>
        <distribution>repo</distribution>
        <comments>Standard open source license.</comments>
    </license>
</licenses>

Purpose:

• Declares the license(s) our project is distributed under.

• Used by tools like Maven Central’s validation process and license scanners.

Key Fields:

• <name> — Full license name.

• <url> — Link to license text.

• <distribution> — Usually repo (distributed with repo) or manual.

• <comments> — Optional notes about the license.

B. <developers>

Example:

<developers>
    <developer>
        <id>pranay</id>
        <name>Pranay Pourkar</name>
        <email>[email protected]</email>
        <url>https://pranaypourkar.dev</url>
        <organization>ConceptJotter</organization>
        <organizationUrl>https://conceptjotter.dev</organizationUrl>
        <roles>
            <role>Developer</role>
            <role>Architect</role>
        </roles>
        <timezone>+5:30</timezone>
    </developer>
</developers>

Purpose:

• Lists the main contributors to the project.

• Important for open-source projects to give credit and contact points.

Key Fields:

• <id> — Short unique identifier.

• <roles> — Multiple roles possible (developer, maintainer, tester, etc.).

• <timezone> — Useful for distributed teams.

C. <contributors>

Example:

<contributors>
    <contributor>
        <name>Jane Doe</name>
        <email>[email protected]</email>
        <roles>
            <role>Tester</role>
        </roles>
    </contributor>
</contributors>

Purpose:

• Recognizes people who contributed but aren’t core developers.

D. <scm> (Source Control Management)

Example:

<scm>
    <connection>scm:git:https://github.com/username/project.git</connection>
    <developerConnection>scm:git:ssh://[email protected]/username/project.git</developerConnection>
    <url>https://github.com/username/project</url>
    <tag>v1.0.0</tag>
</scm>

Purpose:

• Tells Maven and plugins where the source code repository lives.

• Useful for:

  • Automated release tagging

  • Generating SCM links in reports

  • Continuous Integration pipelines

Key Fields:

• <connection> — Read-only access URL.

• <developerConnection> — Write-access URL for maintainers.

• <url> — Web UI link to the repo.

• <tag> — Tag name for the current release.

E. <issueManagement>

Example:

<issueManagement>
    <system>GitHub Issues</system>
    <url>https://github.com/username/project/issues</url>
</issueManagement>

Purpose:

• Indicates where bugs and feature requests are tracked.

F. <ciManagement>

Example:

<ciManagement>
    <system>GitHub Actions</system>
    <url>https://github.com/username/project/actions</url>
</ciManagement>

Purpose:

• Documents the Continuous Integration system for the project.

Best Practices

• Always fill out <licenses> if publishing publicly — Maven Central will reject uploads without it.

• Include <scm> and <developers> for professional credibility.

• Keep metadata updated with each major release.

• For open-source work, align <license> and repository LICENSE file.

Complete Example of pom.xml with All Sections

<?xml version="1.0" encoding="UTF-8"?>
<!-- Maven Project Object Model (POM) File -->
<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">

    <!-- Model Version -->
    <modelVersion>4.0.0</modelVersion>

    <!-- Project Coordinates -->
    <groupId>com.example</groupId>
    <artifactId>demo-project</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <!-- Project Information -->
    <name>Demo Project</name>
    <description>A sample Maven project demonstrating all POM sections.</description>
    <url>https://example.com/demo-project</url>

    <!-- Project Properties -->
    <properties>
        <java.version>17</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>

    <!-- Dependency Management -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>3.2.1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <!-- Project Dependencies -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <!-- Repositories for Dependencies -->
    <repositories>
        <repository>
            <id>central</id>
            <url>https://repo.maven.apache.org/maven2</url>
        </repository>
        <repository>
            <id>jitpack.io</id>
            <url>https://jitpack.io</url>
        </repository>
    </repositories>

    <!-- Build Configuration -->
    <build>
        <finalName>demo-project</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.11.0</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>3.1.2</version>
            </plugin>
        </plugins>
    </build>

    <!-- Profiles for Different Builds -->
    <profiles>
        <profile>
            <id>dev</id>
            <properties>
                <env>development</env>
            </properties>
        </profile>
        <profile>
            <id>prod</id>
            <properties>
                <env>production</env>
            </properties>
        </profile>
    </profiles>

    <!-- Distribution Management for Deployment -->
    <distributionManagement>
        <repository>
            <id>releases-repo</id>
            <url>https://repo.company.com/releases</url>
        </repository>
        <snapshotRepository>
            <id>snapshots-repo</id>
            <url>https://repo.company.com/snapshots</url>
        </snapshotRepository>
        <site>
            <id>project-site</id>
            <url>scp://docs.company.com/www/project</url>
        </site>
        <downloadUrl>https://downloads.company.com/demo-project</downloadUrl>
    </distributionManagement>

    <!-- Reporting Configuration -->
    <reporting>
        <outputDirectory>${project.build.directory}/site</outputDirectory>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-project-info-reports-plugin</artifactId>
                <version>3.4.5</version>
                <reportSets>
                    <reportSet>
                        <reports>
                            <report>dependencies</report>
                            <report>plugins</report>
                            <report>licenses</report>
                        </reports>
                    </reportSet>
                </reportSets>
            </plugin>
            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.8.10</version>
                <reportSets>
                    <reportSet>
                        <reports>
                            <report>report</report>
                        </reports>
                    </reportSet>
                </reportSets>
            </plugin>
        </plugins>
    </reporting>

    <!-- Project Metadata -->
    <licenses>
        <license>
            <name>Apache License, Version 2.0</name>
            <url>https://www.apache.org/licenses/LICENSE-2.0</url>
            <distribution>repo</distribution>
        </license>
    </licenses>

    <developers>
        <developer>
            <id>pranay</id>
            <name>Pranay Pourkar</name>
            <email>[email protected]</email>
            <roles>
                <role>Developer</role>
            </roles>
        </developer>
    </developers>

    <contributors>
        <contributor>
            <name>Jane Doe</name>
            <roles>
                <role>Tester</role>
            </roles>
        </contributor>
    </contributors>

    <scm>
        <connection>scm:git:https://github.com/username/demo-project.git</connection>
        <developerConnection>scm:git:ssh://[email protected]/username/demo-project.git</developerConnection>
        <url>https://github.com/username/demo-project</url>
        <tag>v1.0.0</tag>
    </scm>

    <issueManagement>
        <system>GitHub Issues</system>
        <url>https://github.com/username/demo-project/issues</url>
    </issueManagement>

    <ciManagement>
        <system>GitHub Actions</system>
        <url>https://github.com/username/demo-project/actions</url>
    </ciManagement>

</project>