Simplify Spring Cloud Service Calls with Nacos: RestTemplate, WebClient & Feign

Using RestTemplate

Spring Cloud enhances RestTemplate so that, after a simple configuration, you no longer need to manually concatenate host, IP, and port. By adding @LoadBalanced to the bean definition, the request URL can be written with the service name, and Spring Cloud will resolve it to an actual instance.

<ol>
<li><code>@EnableDiscoveryClient</code></li>
<li><code>@SpringBootApplication</code></li>
<li><code>public class TestApplication { }</code></li>
<li><code>@Slf4j</code></li>
<li><code>@RestController</code></li>
<li><code>static class TestController { }</code></li>
<li><code>@Autowired</code></li>
<li><code>RestTemplate restTemplate;</code></li>
<li><code>@GetMapping("/test")</code></li>
<li><code>public String test() {</code></li>
<li><code>String result = restTemplate.getForObject("http://alibaba-nacos-discovery-server/hello?name=didi", String.class);</code></li>
<li><code>return "Return : " + result;</code></li>
<li><code>}</code></li>
<li><code>@Bean</code></li>
<li><code>@LoadBalanced</code></li>
<li><code>public RestTemplate restTemplate() { return new RestTemplate(); }</code></li>
</ol>

The @LoadBalanced annotation on the RestTemplate bean enables Spring Cloud to intercept the request, select a service instance via the load balancer, and replace the service name with the concrete IP and port.

Using WebClient

WebClient, introduced in Spring 5, is the reactive counterpart of RestTemplate. The usage pattern mirrors the RestTemplate example, but returns a Mono<String> for asynchronous handling.

<ol>
<li><code>@EnableDiscoveryClient</code></li>
<li><code>@SpringBootApplication</code></li>
<li><code>public class TestApplication { }</code></li>
<li><code>@Slf4j</code></li>
<li><code>@RestController</code></li>
<li><code>static class TestController { }</code></li>
<li><code>@Autowired</code></li>
<li><code>WebClient.Builder webClientBuilder;</code></li>
<li><code>@GetMapping("/test")</code></li>
<li><code>public Mono<String> test() {</code></li>
<li><code>Mono<String> result = webClientBuilder.build()</code></li>
<li><code>.get()</code></li>
<li><code>.uri("http://alibaba-nacos-discovery-server/hello?name=didi")</code></li>
<li><code>.retrieve()</code></li>
<li><code>.bodyToMono(String.class);</code></li>
<li><code>return result;</code></li>
<li><code>}</code></li>
<li><code>@Bean</code></li>
<li><code>@LoadBalanced</code></li>
<li><code>public WebClient.Builder loadBalancedWebClientBuilder() { return WebClient.builder(); }</code></li>
</ol>

Just like with RestTemplate, adding @LoadBalanced to the WebClient.Builder bean lets the service name be resolved automatically.

Using Feign

Feign, part of Netflix OSS, provides a declarative way to define service‑consumption interfaces. By enabling @EnableFeignClients and annotating an interface with @FeignClient("alibaba-nacos-discovery-server"), you can call remote endpoints as regular Java methods.

<ol>
<li><code>@EnableDiscoveryClient</code></li>
<li><code>@SpringBootApplication</code></li>
<li><code>@EnableFeignClients</code></li>
<li><code>public class TestApplication { }</code></li>
<li><code>@Slf4j</code></li>
<li><code>@RestController</code></li>
<li><code>static class TestController { }</code></li>
<li><code>@Autowired</code></li>
<li><code>Client client;</code></li>
<li><code>@GetMapping("/test")</code></li>
<li><code>public String test() {</code></li>
<li><code>String result = client.hello("didi");</code></li>
<li><code>return "Return : " + result;</code></li>
<li><code>}</code></li>
<li><code>@FeignClient("alibaba-nacos-discovery-server")</code></li>
<li><code>interface Client {</code></li>
<li><code>@GetMapping("/hello")</code></li>
<li><code>String hello(@RequestParam("name") String name);</code></li>
<li><code>}</code></li>
</ol>

The @EnableFeignClients annotation activates scanning for Feign interfaces, and the @FeignClient annotation binds the interface to the Nacos‑registered service.

Deep Thinking

For developers familiar with Spring Cloud, switching the service registry to Nacos does not affect application code because Spring Cloud abstracts service registration, discovery, and client load balancing behind common interfaces. This abstraction allows seamless replacement of underlying middleware without code changes.

Code Samples

All examples referenced in this article are available in the following repositories:

GitHub: https://github.com/dyc87112/SpringCloud-Learning/

Gitee: https://gitee.com/didispace/SpringCloud-Learning/

Key projects: alibaba-nacos-discovery-server – the service provider (must be started). alibaba-nacos-discovery-client-resttemplate – RestTemplate consumption. alibaba-nacos-discovery-client-webclient – WebClient consumption. alibaba-nacos-discovery-client-feign – Feign consumption.