Master Maven: Essential Dependency Management and Build Techniques for Java Projects

If you have Java development experience, you’ve likely struggled with manually handling JAR files and compatibility issues; Maven simplifies this by managing project builds and dependencies.

Basic Configuration

1. Repository Configuration

Maven uses repositories to store and retrieve JAR files. Developers can rely on the central repository or set up a private repository that Maven checks before falling back to the central one.

2. Basic Project Structure

A minimal Maven project includes groupId, artifactId, and version. Example:

<?xml version="1.0" encoding="UTF-8"?>
<project>
    <!-- Fixed 4.0.0, specifies the POM model version -->
    <modelVersion>4.0.0</modelVersion>
    <groupId>xyz.ibudai</groupId>
    <artifactId>maven-demo</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <description>This is maven demo.</description>
</project>

Dependency Management

1. Adding Dependencies

Use the dependencies tag to declare required libraries:

<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.27</version>
        <scope>runtime</scope>
    </dependency>
</dependencies>

2. Transitive Dependencies

Maven resolves transitive dependencies automatically, so you only need to declare the direct dependency.

3. Dependency Order

Maven follows a “first defined, first imported” rule when multiple versions of the same transitive dependency exist.

4. Excluding Dependencies

Use the excludes tag to prevent specific transitive dependencies from being included.

<dependency>
    <groupId>xyz.ibudai</groupId>
    <artifactId>demo-a</artifactId>
    <version>1.0.0</version>
    <excludes>
        <exclude>
            <groupId>xyz.ibudai</groupId>
            <artifactId>dependency-b</artifactId>
        </exclude>
    </excludes>
</dependency>

5. Optional Dependencies

Mark a dependency as optional to stop it from being transitively propagated.

<dependency>
    <groupId>xyz.ibudai</groupId>
    <artifactId>demo-a</artifactId>
    <version>1.0.0</version>
    <optional>true</optional>
</dependency>

6. Property Variables

Define version numbers and other values in properties and reference them with ${}:

<properties>
    <mysql.version>8.0.30</mysql.version>
    <junit.version>4.13.2</junit.version>
</properties>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>${mysql.version}</version>
</dependency>

Module Configuration

1. Module Management

Define sub‑modules with the modules tag:

<modules>
    <module>module-1</module>
    <module>module-2</module>
</modules>

2. Module Inheritance

Child modules inherit groupId, artifactId, and version from a parent POM via the parent element.

<parent>
    <groupId>xyz.ibudai</groupId>
    <artifactId>maven-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <relativePath>../pom.xml</relativePath>
</parent>

Unified Management

1. Dependency Management

Place common dependency versions in the parent’s dependencyManagement section so child modules can reference them without specifying versions.

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
        </dependency>
    </dependencies>
</dependencyManagement>

Plugin Management

1. Jar Plugin

Customize the JAR manifest using maven-jar-plugin:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>2.3.1</version>
    <configuration>
        <archive>
            <manifest>
                <mainClass>org.example.MyTest</mainClass>
                <addDefaultSpecificationEntries>true</addDefaultSpecificationEntries>
                <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
            </manifest>
            <manifestEntries>
                <Plugin-Id>demo-plugin</Plugin-Id>
                <Plugin-Version>1.0.0</Plugin-Version>
            </manifestEntries>
        </archive>
    </configuration>
</plugin>

2. Assembly Plugin

Package the project together with all its dependencies into a single JAR:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>3.1.0</version>
    <configuration>
        <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
        <finalName>${project.artifactId}-${project.version}-all</finalName>
        <appendAssemblyId>false</appendAssemblyId>
        <attach>false</attach>
    </configuration>
    <executions>
        <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
</plugin>

3. Shade Plugin

Creates an uber‑JAR with optional class relocation and dependency minimization:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>3.2.0</version>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <minimizeJar>true</minimizeJar>
        <artifactSet>
            <includes>
                <include>com.fasterxml.jackson.core:jackson-core</include>
            </includes>
        </artifactSet>
        <relocations>
            <relocation>
                <pattern>com.fasterxml.jackson.core</pattern>
                <shadedPattern>com.ibudai.fasterxml.jackson.core</shadedPattern>
            </relocation>
        </relocations>
        <filters>
            <filter>
                <artifact>*:*</artifact>
                <excludes>
                    <exclude>META-INF/license/**</exclude>
                    <exclude>META-INF/*</exclude>
                    <exclude>LICENSE</exclude>
                    <exclude>NOTICE</exclude>
                </excludes>
            </filter>
        </filters>
    </configuration>
</plugin>

Build Configuration

1. JDK Version

Set the Java source and target versions in the compiler plugin:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.1</version>
    <configuration>
        <source>8</source>
        <target>8</target>
    </configuration>
</plugin>

2. Resource Exclusion

Exclude configuration files from the packaged JAR:

<resources>
    <resource>
        <directory>src/main/resources</directory>
        <excludes>
            <exclude>application.yml</exclude>
        </excludes>
    </resource>
</resources>

3. Main Class

Specify the entry point for the application:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <mainClass>xyz.ibudai.TestWebApplication</mainClass>
        <layout>JAR</layout>
    </configuration>
</plugin>