Design Principles and Module Structure for a Spring Boot Backend Project (XiaoLe)

In this article the author, a senior architect, shares a personal experience of building a backend management system called XiaoLe using Spring Boot, and presents a comprehensive set of design principles for structuring backend modules.

Key Design Principles

Single Responsibility Principle (SRP) : each module should focus on one well‑defined function to reduce complexity.

High Cohesion : related classes and components stay together, improving understandability and maintainability.

Low Coupling : dependencies between modules are minimized so changes in one module do not affect others.

Reusability : modules are built as reusable components that can be shared across projects.

Clear Boundaries and Interfaces : module interfaces are explicit, making interactions obvious for team members.

Moderate Modularity : group related functionality without over‑fragmentation to avoid unnecessary complexity.

Layered Architecture : separate layers such as controller, service, and data‑access to organize code logically.

Dependency Inversion Principle (DIP) : modules depend on abstractions rather than concrete implementations.

Testability : design modules to be easily unit‑tested, integration‑tested, and end‑to‑end tested.

Adaptability for Future Extension : anticipate future requirements so new features can be added with minimal impact.

Project Structure Overview

The project is managed with Maven and consists of several modules: le-admin , le-business , le-common , le-core , le-gen-code , le-tripartite , and a parent POM that aggregates them.

Module Details

Core Module – provides common configuration and foundational services (e.g., Spring Boot core settings, global interceptors, exception handling).

<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.xiaole</groupId>
        <artifactId>XiaoLe</artifactId>
        <version>1.0.0</version>
    </parent>
    <groupId>com.le</groupId>
    <artifactId>le-core</artifactId>
    <name>le-core</name>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
        </dependency>
        <!-- MyBatis -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!-- MySQL driver -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-business</artifactId>
        </dependency>
    </dependencies>
</project>

Common Module – stores utility classes and shared configuration for the whole project.

<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.xiaole</groupId>
        <artifactId>XiaoLe</artifactId>
        <version>1.0.0</version>
    </parent>
    <groupId>com.le</groupId>
    <artifactId>le-common</artifactId>
    <description>common</description>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>
    </dependencies>
</project>

genCode Module – a code‑generation tool that uses Velocity templates to accelerate development.

<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.xiaole</groupId>
        <artifactId>XiaoLe</artifactId>
        <version>1.0.0</version>
    </parent>
    <groupId>com.le</groupId>
    <artifactId>le-gen-code</artifactId>
    <name>le-gen-code</name>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-common</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.velocity</groupId>
            <artifactId>velocity-engine-core</artifactId>
        </dependency>
    </dependencies>
</project>

Business Module – contains the core business logic, services, domain models and data access (MyBatis, Redis, etc.).

<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.xiaole</groupId>
        <artifactId>XiaoLe</artifactId>
        <version>1.0.0</version>
    </parent>
    <groupId>com.le</groupId>
    <artifactId>le-business</artifactId>
    <name>le-business</name>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-common</artifactId>
        </dependency>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-tripartite</artifactId>
        </dependency>
    </dependencies>
</project>

Tripartite Module – handles integration with third‑party services such as payment gateways or external APIs.

<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.xiaole</groupId>
        <artifactId>XiaoLe</artifactId>
        <version>1.0.0</version>
    </parent>
    <groupId>com.le</groupId>
    <artifactId>le-tripartite</artifactId>
    <name>le-tripartite</name>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-common</artifactId>
        </dependency>
    </dependencies>
</project>

Admin Module – provides the management UI and related backend services for administrators.

<?xml version="1.0" encoding="UTF-8"?>
<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.xiaole</groupId>
        <artifactId>XiaoLe</artifactId>
        <version>1.0.0</version>
    </parent>
    <groupId>com.le</groupId>
    <artifactId>le-admin</artifactId>
    <packaging>jar</packaging>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <dependencies>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-gen-code</artifactId>
        </dependency>
        <dependency>
            <groupId>com.le</groupId>
            <artifactId>le-core</artifactId>
        </dependency>
    </dependencies>
</project>

Parent POM – aggregates all modules and manages common dependency versions via dependencyManagement .

<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.xiaole</groupId>
    <artifactId>XiaoLe</artifactId>
    <version>1.0.0</version>
    <packaging>pom</packaging>
    <name>xiaole</name>
    <description>小乐</description>
    <modules>
        <module>le-admin</module>
        <module>le-common</module>
        <module>le-core</module>
        <module>le-business</module>
        <module>le-gen-code</module>
        <module>le-tripartite</module>
    </modules>
    <properties>
        <spring-boot.version>2.5.8</spring-boot.version>
        <xiaole.version>1.0.0</xiaole.version>
        <velocity.version>2.3</velocity.version>
        <mybatis.version>2.2.0</mybatis.version>
    </properties>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.apache.velocity</groupId>
                <artifactId>velocity-engine-core</artifactId>
                <version>${velocity.version}</version>
            </dependency>
            <dependency>
                <groupId>com.le</groupId>
                <artifactId>le-core</artifactId>
                <version>${xiaole.version}</version>
            </dependency>
            <dependency>
                <groupId>com.le</groupId>
                <artifactId>le-admin</artifactId>
                <version>${xiaole.version}</version>
            </dependency>
            <dependency>
                <groupId>com.le</groupId>
                <artifactId>le-common</artifactId>
                <version>${xiaole.version}</version>
            </dependency>
            <dependency>
                <groupId>com.le</groupId>
                <artifactId>le-business</artifactId>
                <version>${xiaole.version}</version>
            </dependency>
            <dependency>
                <groupId>com.le</groupId>
                <artifactId>le-gen-code</artifactId>
                <version>${xiaole.version}</version>
            </dependency>
            <dependency>
                <groupId>com.le</groupId>
                <artifactId>le-tripartite</artifactId>
                <version>${xiaole.version}</version>
            </dependency>
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>${mybatis.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

Why Use import in Spring Boot

The import element in a Maven POM allows a parent project to bring in dependency management and plugin configurations from another POM, enabling modular project organization, version control, and consistent configuration across all modules.

Source Reference

Original article: juejin.cn/post/7319027307578540047