Extending Spring Initializr: From start.spring.io to Alibaba's start.aliyun.com

Background

Spring Initializr (start.spring.io) is widely used to bootstrap Spring Boot projects. Alibaba integrated Nacos and Sentinel, but the generated skeleton only contains component coordinates without usage instructions or demo code, forcing developers to search for tutorials and resolve version mismatches.

Alibaba’s Extension (start.aliyun.com)

Alibaba built a bootstrap site on top of Spring Initializr, adding:

Dedicated demo code and configuration samples for each component.

Built‑in documentation to reduce external look‑ups.

Only “addition” steps required from developers; the platform handles component integration.

Multi‑component integration solutions (in development).

Regular synchronization with start.spring.io to stay up‑to‑date.

The implementation reuses the spring-io/initializr core repository and extends it rather than rewriting the generation engine.

Basic Usage

Add the initializr-bom to the Maven dependencyManagement section:

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>io.spring.initializr</groupId>
      <artifactId>initializr-bom</artifactId>
      <version>0.9.0.BUILD-SNAPSHOT</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

Then include the required modules, e.g. initializr-generator-spring, initializr-version-resolver, and initializr-web.

Configuration (application.yml)

initializr:
  packagings:
    - name: Jar
      id: jar
      default: true
    - name: War
      id: war
      default: false
  javaVersions:
    - id: 13
      default: false
    - id: 11
      default: false
    - id: 1.8
      name: 8
      default: true
  languages:
    - name: Java
      id: java
      default: true
    - name: Kotlin
      id: kotlin
      default: false
    - name: Groovy
      id: groovy
      default: false
  types:
    - name: Maven Project
      id: maven-project
      description: Generate a Maven based project archive.
      tags:
        build: maven
        format: project
      default: true
      action: /starter.zip
    - name: Maven POM
      id: maven-build
      description: Generate a Maven pom.xml.
      tags:
        build: maven
        format: build
      default: false
      action: /pom.xml
    - name: Gradle Project
      id: gradle-project
      description: Generate a Gradle based project archive.
      tags:
        build: gradle
        format: project
      default: false
      action: /starter.zip
    - name: Gradle Config
      id: gradle-build
      description: Generate a Gradle build file.
      tags:
        build: gradle
        format: build
      default: false
      action: /build.gradle

Defining Dependencies

initializr:
  dependencies:
    - name: Web
      content:
        - name: Web
          id: web
          description: Full‑stack web development with Tomcat and Spring MVC
        - name: Spring Boot DevTools
          id: devtools
          groupId: org.springframework.boot
          artifactId: spring-boot-devtools
          description: Fast restarts, LiveReload, and enhanced development experience.
        - name: Lombok
          id: lombok
          groupId: org.projectlombok
          artifactId: lombok
          description: Reduces boilerplate code via annotations.

Each dependency can specify groupId, artifactId, description, optional version, and a compatibilityRange (Maven version range syntax) to restrict supported Spring Boot versions.

Version Management with BOMs

Define a BOM under initializr.env.boms and reference it from components via the bom field. Example:

initializr:
  env:
    boms:
      my-api-bom:
        groupId: org.acme
        artifactId: my-api-dependencies
        version: 1.0.0.RELEASE
        repositories: my-api-repo-1

Component example referencing the BOM:

initializr:
  dependencies:
    - name: Other
      content:
        - name: My API
          id: my-api
          groupId: org.acme
          artifactId: my-api
          bom: my-api-bom

Advanced Customization

Custom demo code can be generated by implementing ProjectContributor beans and conditionally registering them with @ConditionalOnRequestedDependency:

@Bean
@ConditionalOnRequestedDependency("sca-oss")
public OSSDemosContributor ossContributor() {
    return new OSSDemosContributor(description, templateRenderer);
}

Demo files are stored as Mustache templates in resources and rendered during generation.

Internal Mechanics

Project generation consists of two phases:

Startup phase : Loads configuration, registers SPI extensions, and creates beans such as InitializrMetadataProvider, TemplateRenderer, and web controllers.

Generation phase : For each request, a fresh ProjectGenerationContext (a child of the main application context) is created. It registers a ProjectDescriptionProvider, then executes a series of ProjectContributor and *Customizer beans to write files, configure build scripts, and add documentation.

Key extension points: ProjectContributor – writes files to the project directory (e.g., Maven POM, source code, resources). *Customizer – modifies the project model before generation (e.g., MainApplicationTypeCustomizer, BuildCustomizer, GitIgnoreCustomizer).

Extensibility is driven by spring.factories entries that register factories for build systems, languages, packaging, and other modules.

References

Spring Initializr documentation:

https://docs.spring.io/initializr/docs/current-SNAPSHOT/reference/html/

Spring Initializr source code: https://github.com/spring-io/initializr start.spring.io source code:

https://github.com/spring-io/start.spring.io