feat: Add Java Dubbo code generator for Apache Dubbo microservices

[redoom]

Add Dubbo Code Generator

Feature Overview

A new Java Dubbo code generator has been added to OpenAPI Generator, enabling automatic generation of Apache Dubbo-based microservice project code from OpenAPI specifications.

Key Features

Complete Project Generation

• Service Interfaces: Generate standard Dubbo service interfaces
• Service Implementations: Generate service provider implementation classes
• Consumer Controllers: Generate Spring Boot controllers for HTTP access
• Project Configuration: Automatically generate Maven pom.xml and application.yml configurations
• Documentation: Generate detailed README documentation with usage guides

Multi-Version Support

Supports multiple versions of Apache Dubbo with automatic dependency adaptation:

Dubbo Version	Dependency Strategy
3.2 and earlier	Uses aggregated POM dubbo-dependencies-zookeeper
3.3+	Uses modular dependencies dubbo-registry-* + dubbo-remoting-*

Registry Center Support

Supports mainstream registry centers with automatic client version selection:

• Zookeeper: zookeeper://127.0.0.1:2181
• Nacos: nacos://127.0.0.1:8848
  • Dubbo 3.2: nacos-client 2.2.4
  • Dubbo 3.3+: nacos-client 2.5.0

Rich Configuration Options

Configuration	Default Value	Description
title	"OpenAPI Dubbo"	API service title
basePackage	"org.openapitools"	Base package name
dubboVersion	"3.2.18"	Dubbo version
javaVersion	"17"	Java version
interfaceOnly	false	Generate interfaces only, no implementations
serviceInterface	true	Generate service interfaces
serviceImplementation	true	Generate service implementations
useGenericResponse	false	Use generic response wrapper
useTags	true	Use OpenAPI tags to create class names
registry-address	"zookeeper://127.0.0.1:2181"	Registry center address

Generated Project Structure

project-name/
├── src/main/java/org/openapitools/
│   ├── api/
│   │   ├── interfaces/          # Dubbo service interfaces
│   │   │   └── UserService.java
│   │   ├── provider/            # Dubbo service implementations
│   │   │   └── UserServiceImpl.java
│   │   └── consumer/            # Spring Boot controllers
│   │       └── UserController.java
│   ├── model/                   # Data models
│   │   └── User.java
│   └── Application.java         # Main application class
├── src/main/resources/
│   └── application.yml          # Application configuration
├── src/test/java/
│   └── ApplicationTests.java    # Test classes
├── pom.xml                      # Maven configuration
└── README.md                    # Project documentation

Usage Examples

Basic Usage

java -jar openapi-generator-cli.jar generate \
  -i petstore.yaml \
  -g dubbo \
  -o ./generated-dubbo-project

Using Nacos Registry Center

java -jar openapi-generator-cli.jar generate \
  -i petstore.yaml \
  -g dubbo \
  -o ./generated-dubbo-project \
  --additional-properties=registry-address=nacos://127.0.0.1:8848 \
  --additional-properties=dubboVersion=3.3.0 \
  --additional-properties=basePackage=com.example

Generate Interfaces Only

java -jar openapi-generator-cli.jar generate \
  -i petstore.yaml \
  -g dubbo \
  -o ./generated-dubbo-project \
  --additional-properties=interfaceOnly=true \
  --additional-properties=serviceImplementation=false

Technical Implementation

Core Class Structure

• DubboCodegen: Main generator class, extends AbstractJavaCodegen
• Template Files: Located in java-dubbo/ directory
  • api.mustache: Service interface template
  • apiDubbo.mustache: Service implementation template
  • apiController.mustache: Controller template
  • model.mustache: Data model template
  • pom.mustache: Maven configuration template
  • application.mustache: Application configuration template

Intelligent Dependency Management

The generator automatically selects appropriate dependencies based on Dubbo version and registry address:

private boolean isDubbo33OrHigher(String version) {
    // Version parsing logic
    return major > 3 || (major == 3 && minor >= 3);
}

Package Structure Optimization

• interfaces: Pure interface package, can be independently published for consumer reference
• provider: Service provider implementations
• consumer: HTTP gateway controllers

Test Coverage

Generated projects include:

• Spring Boot testing infrastructure
• Application startup tests
• Complete Maven build configuration

Documentation Support

Auto-generated README.md includes:

• Quick start guide
• Registry center configuration instructions
• Project structure description
• Detailed configuration options
• Troubleshooting guide
• Deployment guide

Compatibility

• Java: Supports Java 8+ to Java 21
• Spring Boot: Version 2.7.x
• Maven: Version 3.6+
• Dubbo: Supports all 3.0+ versions

[wing328]

please follow step 3 to update the samples and doc

[wing328]

i've filed #21968 based on this PR with

• some minor fixes
• renaming
• add docs

tests passed. please have a look

[wing328]

closed via #21968