Overview

Master Maven dependency management including dependency declaration, scope management, version resolution, BOMs, and dependency tree optimization.

Overview

Maven's dependency management is a cornerstone of Java project build systems. It handles transitive dependencies, version conflicts, and provides mechanisms for controlling dependency resolution across multi-module projects.

Dependency Declaration

Basic Dependency

xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>3.2.0</version>
</dependency>

Dependency with Scope

xml

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.10.1</version>
    <scope>test</scope>
</dependency>

Optional Dependencies

xml

<dependency>
    <groupId>com.google.code.findbugs</groupId>
    <artifactId>jsr305</artifactId>
    <version>3.0.2</version>
    <optional>true</optional>
</dependency>

Dependency Scopes

Available Scopes

Scope	Compile CP	Test CP	Runtime CP	Transitive
compile	Yes	Yes	Yes	Yes
provided	Yes	Yes	No	No
runtime	No	Yes	Yes	Yes
test	No	Yes	No	No
system	Yes	Yes	No	No
import	N/A	N/A	N/A	N/A

Scope Examples

xml

<!-- Compile scope (default) - available everywhere -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.14.0</version>
</dependency>

<!-- Provided - available at compile, not packaged -->
<dependency>
    <groupId>jakarta.servlet</groupId>
    <artifactId>jakarta.servlet-api</artifactId>
    <version>6.0.0</version>
    <scope>provided</scope>
</dependency>

<!-- Runtime - only needed at runtime -->
<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>42.7.1</version>
    <scope>runtime</scope>
</dependency>

<!-- Test - only for testing -->
<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-core</artifactId>
    <version>5.8.0</version>
    <scope>test</scope>
</dependency>

Version Management

Property-Based Versions

xml

<properties>
    <spring-boot.version>3.2.0</spring-boot.version>
    <junit.version>5.10.1</junit.version>
    <jackson.version>2.16.0</jackson.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <version>${spring-boot.version}</version>
    </dependency>
</dependencies>

Version Ranges

xml

<!-- Exact version -->
<version>1.0.0</version>

<!-- Greater than or equal -->
<version>[1.0.0,)</version>

<!-- Less than -->
<version>(,1.0.0)</version>

<!-- Range inclusive -->
<version>[1.0.0,2.0.0]</version>

<!-- Range exclusive -->
<version>(1.0.0,2.0.0)</version>

Latest Version (Not Recommended)

xml

<!-- Avoid in production -->
<version>LATEST</version>
<version>RELEASE</version>

Dependency Management Section

Centralizing Versions

xml

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>3.2.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson</groupId>
            <artifactId>jackson-bom</artifactId>
            <version>2.16.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<!-- No version needed when declared in dependencyManagement -->
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
    </dependency>
</dependencies>

BOM (Bill of Materials) Import

xml

<dependencyManagement>
    <dependencies>
        <!-- Spring Boot BOM -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>3.2.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>

        <!-- AWS SDK BOM -->
        <dependency>
            <groupId>software.amazon.awssdk</groupId>
            <artifactId>bom</artifactId>
            <version>2.23.0</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>

        <!-- JUnit BOM -->
        <dependency>
            <groupId>org.junit</groupId>
            <artifactId>junit-bom</artifactId>
            <version>5.10.1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

Exclusions

Excluding Transitive Dependencies

xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<!-- Add alternative -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId>
</dependency>

Excluding Logging Frameworks

xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

Dependency Analysis

View Dependency Tree

bash

# Full dependency tree
mvn dependency:tree

# Filter by artifact
mvn dependency:tree -Dincludes=org.slf4j

# Output to file
mvn dependency:tree -DoutputFile=deps.txt

# Verbose output showing conflict resolution
mvn dependency:tree -Dverbose

Analyze Dependencies

bash

# Find unused declared and used undeclared dependencies
mvn dependency:analyze

# Show only problems
mvn dependency:analyze-only

# Include test scope
mvn dependency:analyze -DignoreNonCompile=false

List Dependencies

bash

# List all dependencies
mvn dependency:list

# List with scope
mvn dependency:list -DincludeScope=runtime

Conflict Resolution

Maven's Default Strategy

Maven uses "nearest definition wins" for version conflicts:

A -> B -> C 1.0
A -> C 2.0

Result: C 2.0 is used (nearest to root)

Forcing Versions

xml

<dependencyManagement>
    <dependencies>
        <!-- Force specific version across all modules -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>2.0.9</version>
        </dependency>
    </dependencies>
</dependencyManagement>

Enforcer Plugin for Version Control

xml

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-enforcer-plugin</artifactId>
            <version>3.4.1</version>
            <executions>
                <execution>
                    <id>enforce</id>
                    <goals>
                        <goal>enforce</goal>
                    </goals>
                    <configuration>
                        <rules>
                            <dependencyConvergence/>
                            <requireUpperBoundDeps/>
                            <banDuplicatePomDependencyVersions/>
                        </rules>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Multi-Module Projects

Parent POM Dependency Management

xml

<!-- parent/pom.xml -->
<project>
    <groupId>com.example</groupId>
    <artifactId>parent</artifactId>
    <version>1.0.0</version>
    <packaging>pom</packaging>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.example</groupId>
                <artifactId>common</artifactId>
                <version>${project.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

<!-- module/pom.xml -->
<project>
    <parent>
        <groupId>com.example</groupId>
        <artifactId>parent</artifactId>
        <version>1.0.0</version>
    </parent>

    <artifactId>module</artifactId>

    <dependencies>
        <!-- Version inherited from parent -->
        <dependency>
            <groupId>com.example</groupId>
            <artifactId>common</artifactId>
        </dependency>
    </dependencies>
</project>

Repository Configuration

Central Repository

xml

<repositories>
    <repository>
        <id>central</id>
        <url>https://repo.maven.apache.org/maven2</url>
    </repository>
</repositories>

Private Repository

xml

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

Repository in Settings.xml

xml

<!-- ~/.m2/settings.xml -->
<settings>
    <servers>
        <server>
            <id>company-repo</id>
            <username>${env.REPO_USER}</username>
            <password>${env.REPO_PASS}</password>
        </server>
    </servers>
</settings>

Best Practices

Use dependencyManagement - Centralize versions in parent POMs
Import BOMs - Use well-maintained BOMs for framework dependencies
Avoid Version Ranges - Pin exact versions for reproducibility
Regular Updates - Keep dependencies current for security
Minimize Scopes - Use appropriate scopes to reduce package size
Exclude Unused - Remove unused transitive dependencies
Document Exclusions - Comment why exclusions are needed
Run dependency:analyze - Regularly check for issues
Use Enforcer Plugin - Ensure dependency convergence
Lock Versions - Use versions-maven-plugin for updates

Common Pitfalls

Version Conflicts - Transitive dependency version mismatches
Missing Exclusions - Duplicate classes from different artifacts
Wrong Scope - Compile vs runtime vs provided confusion
Outdated Dependencies - Security vulnerabilities in old versions
Circular Dependencies - Module A depends on B depends on A
Snapshot in Production - Using SNAPSHOT versions in releases
System Scope - Hardcoded paths break portability
Optional Misuse - Marking required dependencies as optional

Troubleshooting

Debug Dependency Resolution

bash

# Enable debug output
mvn dependency:tree -X

# Show conflict resolution
mvn dependency:tree -Dverbose=true

Force Re-download

bash

# Clear local repository cache
mvn dependency:purge-local-repository

# Force update
mvn -U clean install

Check Effective POM

bash

# See resolved dependency versions
mvn help:effective-pom

When to Use This Skill

Adding new dependencies to a project
Resolving version conflicts
Setting up multi-module project dependencies
Configuring BOM imports
Optimizing dependency trees
Troubleshooting classpath issues
Upgrading dependency versions
Excluding problematic transitive dependencies

📖 maven-dependency-management

Overview

Overview

Dependency Declaration

Basic Dependency

Dependency with Scope

Optional Dependencies

Dependency Scopes

Available Scopes

Scope Examples

Version Management

Property-Based Versions

Version Ranges

Latest Version (Not Recommended)

Dependency Management Section

Centralizing Versions

BOM (Bill of Materials) Import

Exclusions

Excluding Transitive Dependencies

Excluding Logging Frameworks

Dependency Analysis

View Dependency Tree

Analyze Dependencies

List Dependencies

Conflict Resolution

Maven's Default Strategy

Forcing Versions

Enforcer Plugin for Version Control

Multi-Module Projects

Parent POM Dependency Management

Repository Configuration

Central Repository

Private Repository

Repository in Settings.xml

Best Practices

Common Pitfalls

Troubleshooting

Debug Dependency Resolution

Force Re-download

Check Effective POM

When to Use This Skill