maven-dependency-management

What this skill does

# Maven Dependency Management

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/>