Resilience4j

https://github.com/spring-boot-tutorials/spring-cloud-circuitbreaker-resilience4j

In this article we will configure Resilience4j in Spring Boot.

Create Initial Code Base

Go to https://start.spring.io/
Add the following dependencies: - spring-cloud-starter-circuitbreaker-resilience4j - spring-boot-starter-web
Click Generate

Dependencies

Dependencies used in pom.xml

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-circuitbreaker-resilience4j</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Service

Create a new file src/main/java/com/example/circuitbreaker_resilience4j/DefaultService.java:

@Service
public class DefaultService {

    @Autowired
    private CircuitBreakerFactory circuitBreakerFactory;

    private final RestTemplate restTemplate = new RestTemplate();

    public String getAlbumList() {
        System.out.println("INSIDE getAlbumList()");

        CircuitBreaker circuitBreaker = circuitBreakerFactory.create("circuitbreaker");
        String url = "http://localhost:1234/not-real";

        return circuitBreaker.run(
                () -> restTemplate.getForObject(url, String.class),
                throwable -> getFallbackAlbumList());
    }

    private String getFallbackAlbumList() {
        System.out.println("INSIDE getFallbackAlbumList()");

        CircuitBreaker circuitBreaker = circuitBreakerFactory.create("circuitbreaker");
        String url = "https://jsonplaceholder.typicode.com/albums";

        return circuitBreaker.run(() -> restTemplate.getForObject(url, String.class));
    }
}

Main

Now let’s use this service.

Go back to MainApplication.java and add the following:

@SpringBootApplication
public class CircuitbreakerResilience4jApplication implements CommandLineRunner {

    public static void main(String[] args) {
            SpringApplication.run(CircuitbreakerResilience4jApplication.class, args);
    }

    @Autowired
    private DefaultService defaultService;

    @Override
    public void run(String... args) throws Exception {
            System.out.println(defaultService.getAlbumList().replace("\n", "").replace("\r", "").replaceAll("\\s+", ""));
    }
}

Run Application

Open terminal at project root and execute the following:

mvn spring-boot:run

There should be no errors and the output will display all the CRUD operations.

Configuration (optional)

See: https://www.baeldung.com/spring-cloud-circuit-breaker#global-custom-configuration

@Configuration
public class DefaultConfiguration {
}