Master Maven: From Basics to Advanced Dependency and Plugin Management

Basic Configuration

Maven introduces the concept of repositories. When a JAR is needed, Maven first checks the local repository; if absent, it downloads from the central repository. Organizations can add private repositories that are consulted before the central one.

Basic Information

A minimal Maven project should define groupId, artifactId, version, name, and description.

<?xml version="1.0" encoding="UTF-8"?>
<project>
  <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

Dependency Introduction

Use the dependencies element to add required libraries. The scope can be compile (default), runtime, provided, or test.

compile : needed at compile time (default)

runtime : not needed at compile time but required at runtime

provided : needed at compile time but supplied by the JDK or server at runtime

test : needed only for test compilation

Transitive Dependencies

Maven resolves transitive dependencies automatically. If Dependency-A depends on Dependency-B, which in turn depends on Dependency-C, Maven will pull Dependency-B and Dependency-C without manual specification.

Dependency Exclusion

When version conflicts arise, use the excludes tag to remove unwanted transitive dependencies. Alternatively, mark a dependency as optional so it is not propagated to downstream projects.

<dependencies>
  <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>
</dependencies>

Module Configuration

Module Management

When a project contains multiple sub‑projects, list them under the modules element.

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

Module Inheritance

A child module can declare a parent pom to inherit all dependency and plugin configurations, including groupId and version. The relativePath points to the parent pom (default ../pom.xml).

<parent>
  <groupId>xyz.ibudai</groupId>
  <artifactId>maven-demo</artifactId>
  <version>1.0-SNAPSHOT</version>
  <relativePath>../pom.xml</relativePath>
</parent>
<artifactId>module-1</artifactId>

Unified Management

Dependency Management

Define common dependencies and their versions once in the parent pom using dependencyManagement. Child modules only need to declare the groupId and artifactId; the version is inherited.

<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

Jar Plugin

The maven-jar-plugin can add custom entries to the JAR manifest.

<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>

Assembly Plugin

The maven-assembly-plugin can create an “uber‑jar” that bundles all dependencies.

<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>
  </configuration>
  <executions>
    <execution>
      <id>make-assembly</id>
      <phase>package</phase>
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Shade Plugin

The maven-shade-plugin also builds an uber‑jar but allows selective inclusion and package relocation to avoid version conflicts.

<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

Version Specification

Set the Java source and target version with the maven-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>

Resource Exclusion

Exclude configuration files (e.g., application.yml) from the packaged JAR.

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

Main Class Configuration

Define the entry point for the application using the mainClass element in the Spring Boot Maven plugin.

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