What is APiGen?

APiGen is an enterprise-grade API generation framework for Java that dramatically accelerates API development by automating repetitive tasks while maintaining full flexibility for customization.

The Problem

Building REST APIs involves significant boilerplate:

• Entity classes with JPA annotations
• DTOs for request/response
• Mappers between entities and DTOs
• Repository interfaces
• Service layer with business logic
• Controllers with CRUD endpoints
• Validation, error handling, pagination
• Security configuration
• Tests for all layers

This typically takes weeks of repetitive work.

The Solution

APiGen provides two approaches:

1. Code Generation

Generate complete project structures from SQL schemas:

./gradlew :generator:cli:run --args="generate \
  --input schema.sql \
  --language java-spring \
  --package com.example.api \
  --output ./my-api"

This generates:

• Entities with proper JPA mappings
• DTOs (request/response)
• MapStruct mappers
• Spring Data repositories
• Service interfaces and implementations
• REST controllers
• Flyway migrations
• Unit and integration tests

2. Runtime Library

Use APiGen as a dependency for instant CRUD:

dependencies {
    implementation 'com.jnzader:apigen-core:1.0.0-SNAPSHOT'
}

@RestController
@RequestMapping("/api/products")
public class ProductController extends CrudController<Product, Long> {
    // All CRUD endpoints are automatic
}

Key Features

Multi-Language Support

Generate APIs in 12+ languages:

Language	Frameworks
Java	Spring Boot, Quarkus
Kotlin	Spring Boot
Python	FastAPI, Django
TypeScript	NestJS, Express
C#	ASP.NET Core
Go	Chi, Gin
PHP	Laravel
Rust	Axum

Enterprise Features

• Auditing: Full change history with Hibernate Envers
• Soft Delete: Logical deletion with restore capability
• Multi-tenancy: Tenant isolation out of the box
• Caching: Caffeine + Redis multi-level cache
• Rate Limiting: Per-endpoint throttling

Observability

• OpenTelemetry distributed tracing
• Prometheus metrics
• Structured JSON logging
• Health checks for Kubernetes

Multiple Protocols

• REST with HATEOAS
• GraphQL with schema stitching
• gRPC for inter-service communication

Architecture

APiGen follows a modular architecture:

┌─────────────────────────────────────────────────────┐
│                    GENERATORS                        │
│  ┌──────────┐  ┌──────────┐  ┌───────────────┐    │
│  │   CLI    │  │  Server  │  │  IDE Plugins  │    │
│  └────┬─────┘  └────┬─────┘  └───────┬───────┘    │
│       └─────────────┼────────────────┘             │
│                     │                               │
│              ┌──────▼──────┐                       │
│              │   Codegen   │                       │
│              │   Engine    │                       │
│              └──────┬──────┘                       │
└─────────────────────┼───────────────────────────────┘
                      │
┌─────────────────────▼───────────────────────────────┐
│                 CORE LIBRARIES                       │
│  ┌──────────┐  ┌──────────┐  ┌────────────────┐   │
│  │   Core   │  │ Security │  │   Exceptions   │   │
│  └──────────┘  └──────────┘  └────────────────┘   │
└─────────────────────────────────────────────────────┘
                      │
┌─────────────────────▼───────────────────────────────┐
│                    FEATURES                          │
│  GraphQL │ gRPC │ Gateway │ Search │ Analytics │... │
└─────────────────────────────────────────────────────┘

When to Use APiGen

Use APiGen when you need:

• Rapid API prototyping
• Consistent project structure across teams
• Enterprise features without custom implementation
• Multi-language API generation
• AI-assisted development (MCP server)

Consider alternatives when:

• Building highly specialized APIs with unique patterns
• Working with non-relational data models
• Requiring extreme customization beyond templates

Next Steps

• Getting Started - Set up your first project
• Quick Start - Generate an API in 5 minutes
• Architecture - Deep dive into the design