Generate Client SDK

Generate Client SDK

Automatically generate type-safe, production-ready client SDKs from OpenAPI/Swagger specifications for multiple programming languages with comprehensive features and documentation.

When to Use This Command

Use /generate-sdk when you need to:

• Create official client libraries for your API
• Ensure type safety across different programming languages
• Maintain SDK consistency with API changes
• Reduce manual SDK maintenance overhead
• Provide developers with intuitive API clients
• Support multiple programming languages

DON'T use this when:

• Your API lacks proper OpenAPI documentation (create spec first)
• Building internal-only APIs with single consumer (direct integration may be simpler)
• API is still rapidly changing (wait for stability)

Design Decisions

This command implements OpenAPI Generator as the primary approach because:

• Supports 50+ programming languages and frameworks
• Active community with regular updates
• Customizable templates for each language
• Generates both client and server code
• Comprehensive documentation generation
• Battle-tested in production environments

Alternative considered: Swagger Codegen

• Original OpenAPI code generator
• Less frequent updates
• Fewer customization options
• Recommended for legacy projects

Alternative considered: Custom generators

• Full control over generated code
• Better for specific requirements
• Higher maintenance burden
• Recommended only for unique needs

Prerequisites

Before running this command:

1. Complete OpenAPI specification (v3.0 or v3.1)
2. Validate spec with OpenAPI validators
3. Define authentication schemes
4. Document all endpoints and models
5. Choose target languages and versions

Implementation Process

Step 1: Validate OpenAPI Specification

Ensure your OpenAPI spec is complete, valid, and includes all necessary details.

Step 2: Configure Generator Options

Set language-specific options like package names, versions, and dependencies.

Step 3: Generate SDK Code

Run the generator for each target language with customized templates.

Step 4: Add Custom Enhancements

Implement additional features like retry logic, caching, or specialized authentication.

Step 5: Package and Distribute

Create distribution packages for each language's package manager.

Output Format

The command generates:

• sdks/javascript/ - Node.js/Browser SDK with TypeScript definitions
• sdks/python/ - Python SDK with type hints
• sdks/java/ - Java SDK with Maven/Gradle support
• sdks/go/ - Go SDK with modules
• docs/sdk-usage.md - Usage documentation for all SDKs
• examples/ - Working examples for each language

Code Examples

Example 1: TypeScript SDK Generation and Usage

# openapi.yaml
openapi: 3.0.0
info:
  title: E-commerce API
  version: 1.0.0
servers:
  - url: https://api.example.com/v1
paths:
  /products:
    get:
      operationId: listProducts
      parameters:
        - name: category
          in: query
          schema:
            type: string
        - name: limit
          in: query
          schema:
            type: integer
            default: 20
      responses:
        '200':
          description: Product list
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Product'
  /products/{productId}:
    get:
      operationId: getProduct
      parameters:
        - name: productId
          in: path
          required: true
          schema:
            type: string
            format: uuid
      responses:
        '200':
          description: Product details
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Product'
components:
  schemas:
    Product:
      type: object
      required:
        - id
        - name
        - price
      properties:
        id:
          type: string
          format: uuid
        name:
          type: string
        description:
          type: string
        price:
          type: number
          format: double
        category:
          type: string
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

# Generate TypeScript SDK
npx @openapitools/openapi-generator-cli generate \
  -i openapi.yaml \
  -g typescript-axios \
  -o ./sdks/typescript \
  --additional-properties=\
npmName=@company/api-client,\
npmVersion=1.0.0,\
supportsES6=true,\
withInterfaces=true

// sdks/typescript/src/index.ts (generated)
import { Configuration, ProductsApi } from '@company/api-client';

// Enhanced configuration with retry and interceptors
export class ApiClient {
  private config: Configuration;
  private productsApi: ProductsApi;
  private retryConfig = {
    retries: 3,
    retryDelay: 1000,
    retryCondition: (error: any) => {
      return error.response?.status >= 500;
    }
  };

  constructor(apiKey?: string, basePath?: string) {
    this.config = new Configuration({
      basePath: basePath || 'https://api.example.com/v1',
      accessToken: apiKey,
      baseOptions: {
        timeout: 10000,
        headers: {
          'User-Agent': '@company/api-client/1.0.0'
        }
      }
    });

    this.productsApi = new ProductsApi(this.config);
    this.setupInterceptors();
  }

  private setupInterceptors() {
    // Request interceptor for logging
    this.config.baseOptions.transformRequest = [
      (data, headers) => {
        console.log('API Request:', { data, headers });
        return data;
      }
    ];

    // Response interceptor for error handling
    this.config.baseOptions.validateStatus = (status) => {
      return status >= 200 && status < 300;
    };
  }

  async getProducts(options?: {
    category?: string;
    limit?: number;
  }): Promise<Product[]> {
    try {
      const response = await this.withRetry(() =>
        this.productsApi.listProducts(
          options?.category,
          options?.limit
        )
      );
      return response.data;
    } catch (error) {
      this.handleError(error);
      throw error;
    }
  }

  async getProduct(productId: string): Promise<Product> {
    try {
      const response = await this.withRetry(() =>
        this.productsApi.getProduct(productId)
      );
      return response.data;
    } catch (error) {
      this.handleError(error);
      throw error;
    }
  }

  private async withRetry<T>(
    fn: () => Promise<T>,
    retriesLeft = this.retryConfig.retries
  ): Promise<T> {
    try {
      return await fn();
    } catch (error) {
      if (retriesLeft > 0 && this.retryConfig.retryCondition(error)) {
        await this.delay(this.retryConfig.retryDelay);
        return this.withRetry(fn, retriesLeft - 1);
      }
      throw error;
    }
  }

  private delay(ms: number): Promise<void> {
    return new Promise(resolve => setTimeout(resolve, ms));
  }

  private handleError(error: any) {
    if (error.response) {
      console.error('API Error:', {
        status: error.response.status,
        data: error.response.data
      });
    } else if (error.request) {
      console.error('Network Error:', error.message);
    } else {
      console.error('Error:', error.message);
    }
  }
}

// Usage example
const client = new ApiClient('your-api-key');

// Get products with automatic retry and error handling
const products = await client.getProducts({
  category: 'electronics',
  limit: 50
});

// Get single product
const product = await client.getProduct('550e8400-e29b-41d4-a716-446655440000');

Example 2: Python SDK Generation with Enhanced Features

# Generate Python SDK
openapi-generator-cli generate \
  -i openapi.yaml \
  -g python \
  -o ./sdks/python \
  --additional-properties=\
packageName=company_api,\
packageVersion=1.0.0,\
projectName=company-api-client

# sdks/python/company_api/enhanced_client.py
import time
import logging
from typing import Optional, Dict, Any, List
from functools import wraps
import requests
from requests.adapters import HTTPAdapter
from requests.packages.urllib3.util.retry import Retry

from company_api import Configuration, ApiClient
from company_api.api import ProductsApi
from company_api.models import Product

logger = logging.getLogger(__name__)

def retry_on_failure(max_retries=3, delay=1):
    """Decorator for retrying failed API calls."""
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            last_exception = None
            for attempt in range(max_retries):
                try:
                    return func(*args, **kwargs)
                except Exception as e:
                    last_exception = e
                    if attempt < max_retries - 1:
                        wait_time = delay * (2 ** attempt)  # Exponential backoff
                        logger.warning(
                            f"Attempt {attempt + 1} failed: {e}. "
                            f"Retrying in {wait_time} seconds..."
                        )
                        time.sleep(wait_time)
                    else:
                        logger.error(f"All {max_retries} attempts failed")
            raise last_exception
        return wrapper
    return decorator

class EnhancedApiClient:
    """Enhanced API client with retry logic, caching, and connection pooling."""

    def __init__(
        self,
        api_key: Optional[str] = None,
        base_url: Optional[str] = None,
        timeout: int = 30,
        max_retries: int = 3
    ):
        # Configure base client
        config = Configuration()
        config.host = base_url or "https://api.example.com/v1"
        if api_key:
            config.api_key['Authorization'] = api_key
            config.api_key_prefix['Authorization'] = 'Bearer'

        # Set up session with connection pooling
        session = requests.Session()
        retry_strategy = Retry(
            total=max_retries,
            backoff_factor=1,
            status_forcelist=[429, 500, 502, 503, 504],
        )
        adapter = HTTPAdapter(
            max_retries=retry_strategy,
            pool_connections=10,
            pool_maxsize=10
        )
        session.mount("http://", adapter)
        session.mount("https://", adapter)

        self.api_client = ApiClient(configuration=config)
        self.api_client.rest_client.session = session
        self.products_api = ProductsApi(self.api_client)
        self.timeout = timeout
        self._cache: Dict[str, Any] = {}

    @retry_on_failure(max_retries=3, delay=1)
    def list_products(
        self,
        category: Optional[str] = None,
        limit: Optional[int] = 20,
        use_cache: bool = True
    ) -> List[Product]:
        """List products with optional caching."""
        cache_key = f"products_{category}_{limit}"

        if use_cache and cache_key in self._cache:
            logger.info(f"Returning cached results for {cache_key}")
            return self._cache[cache_key]

        try:
            response = self.products_api.list_products(
                category=category,
                limit=limit,
                _request_timeout=self.timeout
            )

            if use_cache:
                self._cache[cache_key] = response
                logger.info(f"Cached results for {cache_key}")

            return response
        except Exception as e:
            logger.error(f"Failed to list products: {e}")
            raise

    @retry_on_failure(max_retries=3, delay=1)
    def get_product(
        self,
        product_id: str,
        use_cache: bool = True
    ) -> Product:
        """Get product details with optional caching."""
        cache_key = f"product_{product_id}"

        if use_cache and cache_key in self._cache:
            logger.info(f"Returning cached product {product_id}")
            return self._cache[cache_key]

        try:
            response = self.products_api.get_product(
                product_id=product_id,
                _request_timeout=self.timeout
            )

            if use_cache:
                self._cache[cache_key] = response
                logger.info(f"Cached product {product_id}")

            return response
        except Exception as e:
            logger.error(f"Failed to get product {product_id}: {e}")
            raise

    def clear_cache(self, pattern: Optional[str] = None):
        """Clear cache entries matching pattern."""
        if pattern:
            keys_to_remove = [
                k for k in self._cache.keys()
                if pattern in k
            ]
            for key in keys_to_remove:
                del self._cache[key]
            logger.info(f"Cleared {len(keys_to_remove)} cache entries")
        else:
            self._cache.clear()
            logger.info("Cleared all cache entries")

# Usage example
if __name__ == "__main__":
    # Configure logging
    logging.basicConfig(level=logging.INFO)

    # Initialize client
    client = EnhancedApiClient(
        api_key="your-api-key",
        timeout=30,
        max_retries=3
    )

    # List products with automatic retry and caching
    products = client.list_products(
        category="electronics",
        limit=50,
        use_cache=True
    )
    print(f"Found {len(products)} products")

    # Get specific product
    product = client.get_product("550e8400-e29b-41d4-a716-446655440000")
    print(f"Product: {product.name} - ${product.price}")

Example 3: Multi-Language SDK Generation Script

#!/bin/bash
# generate-all-sdks.sh

SPEC_FILE="openapi.yaml"
OUTPUT_DIR="./sdks"
VERSION="1.0.0"

# Validate OpenAPI spec first
echo "Validating OpenAPI specification..."
npx @stoplight/spectral-cli lint $SPEC_FILE

if [ $? -ne 0 ]; then
    echo "OpenAPI spec validation failed"
    exit 1
fi

# Generate TypeScript SDK
echo "Generating TypeScript SDK..."
npx @openapitools/openapi-generator-cli generate \
  -i $SPEC_FILE \
  -g typescript-axios \
  -o $OUTPUT_DIR/typescript \
  --additional-properties=\
npmName=@company/api-client,\
npmVersion=$VERSION,\
supportsES6=true,\
withInterfaces=true

# Generate Python SDK
echo "Generating Python SDK..."
openapi-generator-cli generate \
  -i $SPEC_FILE \
  -g python \
  -o $OUTPUT_DIR/python \
  --additional-properties=\
packageName=company_api,\
packageVersion=$VERSION

# Generate Java SDK
echo "Generating Java SDK..."
openapi-generator-cli generate \
  -i $SPEC_FILE \
  -g java \
  -o $OUTPUT_DIR/java \
  --additional-properties=\
groupId=com.company,\
artifactId=api-client,\
artifactVersion=$VERSION,\
library=okhttp-gson

# Generate Go SDK
echo "Generating Go SDK..."
openapi-generator-cli generate \
  -i $SPEC_FILE \
  -g go \
  -o $OUTPUT_DIR/go \
  --additional-properties=\
packageName=company,\
packageVersion=$VERSION

# Generate documentation
echo "Generating SDK documentation..."
for lang in typescript python java go; do
  echo "## $lang SDK" >> $OUTPUT_DIR/README.md
  echo "See $OUTPUT_DIR/$lang for implementation" >> $OUTPUT_DIR/README.md
done

echo "SDK generation complete!"

Error Handling

Configuration Options

Generator Options

• library: HTTP client library to use
• dateLibrary: Date handling library
• useSingleRequestParameter: Bundle parameters
• nullableFields: Generate nullable types
• enumUnknownDefaultCase: Handle unknown enums

Language-Specific Options

• TypeScript: npmRepository, withoutPrefixEnums
• Python: packageUrl, useNose, asyncio
• Java: serializationLibrary, useRuntimeException
• Go: isGoSubmodule, structPrefix

Best Practices

DO:

• Keep OpenAPI spec as single source of truth
• Version SDKs alongside API versions
• Include comprehensive examples
• Generate SDKs in CI/CD pipeline
• Add language-specific enhancements
• Publish to package registries

DON'T:

• Manually edit generated code (use templates)
• Skip OpenAPI validation before generation
• Ignore breaking changes in API
• Forget to update SDK documentation
• Mix generated and custom code

Performance Considerations

• Use connection pooling for better performance
• Implement client-side caching where appropriate
• Add request/response compression support
• Consider pagination for large result sets
• Implement circuit breakers for resilience

Related Commands

• /api-documentation-generator - Generate API docs
• /api-contract-generator - Create OpenAPI specs
• /api-testing-framework - Test SDKs
• /api-versioning-manager - Handle API versions

Version History

• v1.0.0 (2024-10): Initial implementation with OpenAPI Generator support
• Planned v1.1.0: Add GraphQL and gRPC SDK generation