How to Build a Spring Boot Multi‑Module Project with Maven

Why Use Multiple Modules?

In modern software development, modular design improves maintainability and team collaboration. For a large enterprise application with features like user management, order processing, and payment, a single project becomes unwieldy. Splitting functionality into independent sub‑modules (module-a, module-b, module-c) clarifies structure and boosts efficiency.

Project Structure

A typical Spring Boot + Maven multi‑module layout looks like:

my-multi-module-project
│
├── pom.xml
├── module-a
│   └── pom.xml
├── module-b
│   └── pom.xml
└── module-c
    └── pom.xml

Here

my-multi-module-project

is the parent project, while

module-a

,

module-b

, and

module-c

are child modules. Each child has its own

pom.xml

, and the parent’s

pom.xml

manages dependencies and build configuration.

Create Parent Project

The parent

pom.xml

defines the modules and common dependencies, for example:

<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">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.example</groupId>
  <artifactId>my-multi-module-project</artifactId>
  <version>1.0.0-SNAPSHOT</version>
  <packaging>pom</packaging>

  <modules>
    <module>module-a</module>
    <module>module-b</module>
    <module>module-c</module>
  </modules>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-dependencies</artifactId>
        <version>2.5.4</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

The parent pom lists the three sub‑modules and imports Spring Boot’s dependency management.

Create Sub‑Modules

Each sub‑module needs its own

pom.xml

. For

module-a

:

<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">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>com.example</groupId>
    <artifactId>my-multi-module-project</artifactId>
    <version>1.0.0-SNAPSHOT</version>
  </parent>

  <artifactId>module-a</artifactId>

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

The

<parent>

tag links the child to the parent and brings in Spring Boot dependencies.

Write Code

In

module-a

create a simple Spring Boot application:

package com.example.modulea;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

And a basic controller:

package com.example.modulea.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String sayHello() {
        return "Hello from Module A!";
    }
}

Run the Project

Build and run the whole project with Maven:

mvn clean install
mvn spring-boot:run -pl module-a

Access

http://localhost:8080/hello

in a browser to see the response “Hello from Module A!”.

Conclusion

This guide demonstrated how to set up a Spring Boot multi‑module Maven project, covering project layout, parent and child pom configuration, sample code, and execution steps, helping developers apply modular design in real projects.