Using Netflix Ribbon without Spring Boot in Legacy Application

Question

I work at an application which is using Apache Mina as SFTP Server. The application itself is started as jar and sends rest requests to our backend.

I now want to use Netflix Ribbon without turning the whole application into a spring boot project or spring project in general.

My approach is to access the api directly like in the example:

public class MyClass {
    @Autowired
    private LoadBalancerClient loadBalancer;

    public void doStuff() {
        ServiceInstance instance = loadBalancer.choose("stores");
        URI storesUri = URI.create(String.format("http://%s:%s", instance.getHost(), instance.getPort()));
        // ... do something with the URI
    }
}

Examples in the documentation only show how it is done if configuration is done by spring automatically. However this is not working for me and I cannot get spring to automatically provide the loadbalancer bean.

Answer 1

I solved the problem by "hardcoding" the spring parts:

@Configuration
public class LoadbalancerConfig {

    @Bean
    public ILoadBalancer loadBalancer() {
        BaseLoadBalancer baseLoadBalancer = new BaseLoadBalancer("balancer", rule(), new LoadBalancerStats("balancer"));
        baseLoadBalancer.addServers(serverList().getInitialListOfServers());
        return baseLoadBalancer;
    }

    @Bean
    public IRule rule() {
        return new RandomRule();
    }

    @Bean
    public ServerList<Server> serverList() {
        return new StaticServerList<>((new Server("host1", 80)),
                new Server("host2", 80));
    }
}

Util class for getting bean at later point:

public class BeanUtil implements ApplicationContextAware {

    private static final Logger log = LogManager.getLogger(BeanUtil.class);
    private static ApplicationContext applicationContext;


    @Override
    public void setApplicationContext(final ApplicationContext ctx) throws BeansException {
        applicationContext = ctx;
    }

  
    public static <T> T getBean(Class<T> beanClass) {
        
        return applicationContext.getBean(beanClass);
    }
}

I initiate them through a xml file:

<context:component-scan base-package="package.of.loadbalancerconfig" />
<bean id="applicationContextProvider" lazy-init="false" class="my.package.BeanUtil" />

Dont forget to create your applicationContext at initialization:

ApplicationContext context = new FileSystemXmlApplicationContext("file:/path/to/beans.xml");

Now I could get the loadbalancer and the instances:

 if (loadBalancer == null) {
        loadBalancer = BeanUtil.getBean(ILoadBalancer.class);
 }
 Server instance = loadBalancer.chooseServer("balancer");
 URI uri = URI.create(String.format("http://%s:%s", instance.getHost(), instance.getPort()));

I'm sure there is a more elegant way, but it worked for me.