Spring Cloud API Gateway

Spring Cloud Gateway is a framework for building API gateways on top of Spring Webflux framework.
It provides a reverse proxy to handle requests and perform various routing-related tasks, such as request forwarding, request filtering, and request transformation. This can help you simplify your microservice architecture and improve the performance and security of your application.

Here is an example of how you can create a Spring Cloud API Gateway in a Spring Boot application along with a simple car microservice.

API Gateway:

First, create a Spring Boot project and add the following dependencies to your pom.xml file:

<dependencies>
    <dependency>
        <groupid>org.springframework.cloud</groupid>
        <artifactid>spring-cloud-starter-gateway</artifactid>
    </dependency>
</dependencies>

<groupid>org.springframework.cloud</groupid>

<artifactid>spring-cloud-starter-gateway</artifactid>

</dependency>

</dependencies>

Next, add the following code to your main class to enable the gateway:

@SpringBootApplication
public class ApiGatewayApplication {
    public static void main(String[] args) {
        SpringApplication.run(ApiGatewayApplication.class, args);
    }
}

@SpringBootApplication

public class ApiGatewayApplication {

public static void main(String[] args) {

SpringApplication.run(ApiGatewayApplication.class, args);

}

Car Microservice:

Create another Spring Boot project and add the following REST endpoint in your main class:

@RestController
public class CarController {
    @GetMapping("/car")
    public String getCar() {
        return "Audi";
    }
}

@RestController

public class CarController {

@GetMapping("/car")

public String getCar() {

return "Audi";

}

And add the following properties to your application.properties or application.yml file:

server.port: 8081

1 2	server.port: 8081

Configure the Gateway:

Create a new file named application.yml in the API Gateway project and add the following code:

spring:
  cloud:
    gateway:
      routes:
      - id: car-service
        uri: http://localhost:8081
        predicates:
        - Path=/car-service/**
        filters:
        - StripPrefix=1

spring:

cloud:

gateway:

routes:

- id: car-service

uri: http://localhost:8081

predicates:

- Path=/car-service/**

filters:

- StripPrefix=1

This configuration maps the /car-service/** path to the car microservice running at http://localhost:8081. The StripPrefix filter is used to strip the first path element from the request, which corresponds to the /car-service part of the URL.

That’s it! You can now run both the API gateway and the car microservice. You can access the car endpoint through the API gateway by making a GET request to http://localhost:8080/car, where 8080 is the default port of the API gateway.

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