🚀 Spring Cloud Gateway – REST, gRPC & Web Router

A unified API Gateway built with Spring Cloud Gateway that supports routing for:

• ✅ REST APIs (HTTP/1.1)
• ✅ gRPC Services (HTTP/2 + TLS)
• ✅ Web Applications (React etc.)
• ✅ Custom Filters
• ✅ SSL / mTLS Support
• ✅ Load Balancing Ready

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🏗 Architecture Overview

                 ┌─────────────────────┐
                 │     React App       │
                 │   (Frontend SPA)    │
                 └──────────┬──────────┘
                            │
                            ▼
                 ┌─────────────────────┐
                 │  Spring Cloud       │
                 │      Gateway        │
                 │  (HTTP1 + HTTP2)    │
                 └───────┬───────┬─────┘
                         │       │
                         ▼       ▼
                ┌──────────┐   ┌──────────┐
                │  REST    │   │  gRPC    │
                │ Service  │   │ Service  │
                └──────────┘   └──────────┘

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⚙️ Technologies Used

• ☕ Java 25
• ⚡ Gradle
• 🌱 Spring Boot
• 🌐 Spring Cloud Gateway
• 🔄 Reactor Netty
• 📡 REST (HTTP/1)
• 📡 gRPC (HTTP/2)
• 🔐 TLS / SSL (PKCS12 / JKS / PEM)

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📦 Features

1️⃣ REST Routing (HTTP/1.1)

• Path-based routing
• Load balancing support
• Custom filters
• Header manipulation
• Authentication ready

Example:

GET /api/users
→ Forward to http://localhost:8081

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2️⃣ gRPC Routing (HTTP/2 + TLS)

• HTTP/2 support
• TLS secured channel
• Custom ServerWebExchange URI rewriting
• Supports internal PKCS12 bundle
• Compatible with spring-grpc or Netty server

Example:

service UserService {
  rpc GetUser(UserRequest) returns (UserResponse);
}

Gateway forwards:

https://gateway:9090/grpc/UserService
→ https://localhost:50051

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3️⃣ Web / React App Forwarding

• SPA routing support
• Static content proxy
• Supports HTTPS certificates
• Works with custom SSL setup

Example:

https://gateway:9090/app
→ https://localhost:3000

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🔐 SSL Configuration

Supports:

• PKCS12 (.p12)
• JKS
• PEM (.crt + .key)
• Self-signed certificates
• mTLS (optional)

Example application.properties:

server.port=9090
server.ssl.enabled=true
server.ssl.key-store=classpath:gateway.p12
server.ssl.key-store-password=changeit
server.ssl.key-store-type=PKCS12
server.http2.enabled=true

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📂 Project Structure

spring-cloud-gateway/
│
├── src/main/java/
│   ├── config/
│   ├── filter/
│   ├── route/
│   └── GatewayApplication.java
│
├── src/main/resources/
│   ├── application.properties
│   └── ssl/
│
└── build.gradle

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🛠 Custom Filters Example

@Component
public class GrpcRoutingFilter implements GlobalFilter, Ordered {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange,
                             GatewayFilterChain chain) {

        URI newUri = URI.create("https://localhost:50051");
        exchange.getAttributes()
                .put(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR, newUri);

        return chain.filter(exchange);
    }

    @Override
    public int getOrder() {
        return -1;
    }
}

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▶️ Running the Project

1️⃣ Build

./gradlew clean build

2️⃣ Run

./gradlew bootRun

or

java -jar build/libs/gateway.jar

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🤝 Contributing

Pull requests are welcome!

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📄 License

MIT License