Spring cloud eureka simple example

work process:

1. The service provider registers the service to the service registry.

2. The service consumer goes to the registry to obtain a list of providers.

3. The service consumer uses the service provided by the provider.

 

First create a new maven project, add dependency in pom.xml

<parent>
	<artifactId>spring-boot-starter-parent</artifactId>
	<groupId>org.springframework.boot</groupId>
	<version>1.5.2.RELEASE</version>
	<relativePath />
</parent>

<dependencies>
	<dependency>
		<groupId>org.springframework.cloud</groupId>
		<artifactId>spring-cloud-starter-eureka</artifactId>
		<version>1.3.2.RELEASE</version>
	</dependency>
	<dependency>
		<groupId>org.springframework.cloud</groupId>
		<artifactId>spring-cloud-starter-eureka-server</artifactId>
		<version>1.3.2.RELEASE</version>
	</dependency>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-jetty</artifactId>
	</dependency>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-test</artifactId>
	</dependency>
	<dependency>
		<groupId>javax.servlet</groupId>
		<artifactId>javax.servlet-api</artifactId>
	</dependency>
</dependencies>

 

In this simple example, the registry, the service provider and the service consumer are in one project, so the profiles are used to distinguish different settings.

 

 

Start the Eureka registry server

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
	public static void main(String[] args) {
		System.setProperty("spring.profiles.active", "server");
		SpringApplication.run(EurekaServerApplication.class, args);
	}
}

 Corresponding application-server.properties

spring.application.name=eurekaserver
server.port=1001
eureka.instance.hostname=localhost
eureka.client.fetch-registry=false
eureka.client.register-with-eureka=false
eureka.client.serviceUrl.defaultZone=http://localhost:1001/eureka/

Visit http://localhost:1001/ to view the running status of the Eureka registry.

 

 

Start the service provider:

@SpringBootApplication
@EnableDiscoveryClient
public class EurekaApplication {
	public static void main(String[] args) {
		System.setProperty("spring.profiles.active", "provider");
		SpringApplication.run(EurekaApplication.class, args);
	}
}

 In addition, a REST service is provided on the Service Provider:

@RestController
public class HelloController {
	@RequestMapping("/hello")
	public String index() {
		System.out.println("index is called");
		return "Hello World";
	}
}

 Application-provider.properties corresponding to Service provider

spring.application.name=hello
server.port=1201
eureka.client.serviceUrl.defaultZone=http://localhost:1001/eureka/

This will register your service to the Eureka registry. 

 

The consumer that finally starts the service:

@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {
	
	@Bean
	@LoadBalanced
	public RestTemplate restTemplate() {
		return new RestTemplate ();
	}

	public static void main(String[] args) {
		System.setProperty("spring.profiles.active", "consumer");
		SpringApplication.run(ConsumerApplication.class, args);
	}
}

 And a REST Controller provided by the service consumer, which will call the Provider's REST service.

@RestController
public class ConsumerCotroller {
	@Autowired
	private RestTemplate template;
	
	@RequestMapping("/consumer")
	public String index() {
		return template.getForEntity("http://HELLO/hello", String.class).getBody();
	}
}

 application-consumer.properties corresponding to service consumers

server.port=9000
spring.application.name=hello-consumer
eureka.client.serviceUrl.defaultZone=http://localhost:1001/eureka/

 

The structure of the entire project is shown in the figure:

 

Visit http://localhost:9000/consumer and you will see Hello World.

 

The source code can be downloaded from  https://github.com/21ca/eureka-demo .

 

In this source code example, two service registries are started to form a registry cluster. Then start two service providers and register with different service registries respectively. The service consumer gets the list of providers from the registry, and then calls (client-side load balancing) the services of the service provider respectively.