Using Nacos for service discovery in Java API development

With the rise of cloud-native applications, microservice architecture is increasingly favored by developers. Service discovery is an essential part of the microservice architecture, which allows services to register themselves and communicate with other services. In Java development, Nacos is a popular open source service discovery and configuration center. It provides easy-to-use API and UI interfaces, allowing developers to better manage and coordinate services. This article will introduce how to use Nacos for service discovery in Java API development.

1. Installing Nacos

First, you need to download and install Nacos. Nacos provides two installation methods: compiling from source code and installing through binary packages. Here, we choose to install via binary package.

Download address: https://github.com/alibaba/nacos/releases

After the download is completed, decompress and start the Nacos service. Create namespaces and services in the Nacos console to facilitate unified management of services.

2. Introducing dependencies

In the Gradle or Maven project, add the dependency of the Nacos client:

Gradle:

implementation 'com.alibaba.nacos:nacos-client:2.0.1'

Maven ：

<dependency>
  <groupId>com.alibaba.nacos</groupId>
  <artifactId>nacos-client</artifactId>
  <version>2.0.1</version>
</dependency>

3. Writing service consumers

When writing service consumers, you need to use the DiscoveryClient object provided by Nacos to obtain all available service instances and provide them for future requests. Select an instance.

import com.alibaba.cloud.nacos.NacosDiscoveryProperties;
import com.alibaba.cloud.nacos.discovery.NacosDiscoveryClient;
import com.alibaba.nacos.api.exception.NacosException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.List;

@Component
public class ServiceConsumer {
    @Autowired
    private NacosDiscoveryProperties discoveryProperties;

    public String getServiceUrl(String serviceName) throws NacosException {
        NacosDiscoveryClient nacosDiscoveryClient = new NacosDiscoveryClient(discoveryProperties);
        List<Instance> instances = nacosDiscoveryClient.getInstances(serviceName);
        if (CollectionUtils.isEmpty(instances)) {
            throw new RuntimeException("No available instance for service");
        }
        Instance instance = LoadBalancer.chooseInstance(instances);
        return instance.getUri().toString();
    }
}

In the above code, we get the list of service instances through DiscoveryClient and select a service instance using LoadBalancer. You can customize LoadBalancer to suit your needs.

4. Writing a service provider

When writing a service provider, you need to register the service with Nacos and implement the specific business logic of the service.

import com.alibaba.cloud.nacos.registry.NacosRegistration;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@EnableDiscoveryClient
@RestController
public class ServiceProvider {
    @Autowired
    private NacosRegistration registration;

    @Value("${server.port}")
    private int port;

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

    @GetMapping("/")
    public String index() {
        return "Hello, world!";
    }

    @GetMapping("/register")
    public String register() {
        registration.register();
        return "服务注册成功";
    }
}

In the above code, we use NacosRegistration to register the service to Nacos and provide the service in the controller.

5. Run the service

Now, we can start the service provider and service consumer, and access the services provided by the service provider through the service consumer.

Visit http://localhost:8080/register to register the service into Nacos.

Visit http://localhost:8080/, you can see the content returned by the service provider.

6. Summary

This article introduces how to use Nacos for service discovery in Java API development. Using Nacos, services can be easily registered and discovered, and no additional coding is required to achieve high availability of services. I hope this article can be helpful to Java developers.

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