Java uses Eureka to achieve client load balancing
1. Maven coordinates:
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
</dependencies>
2. Brief introduction:
`Spring cloud starter netflix eureka client 'is part of the Spring Cloud Netflix project, used to integrate with Eureka Server in Java applications, achieve service registration and discovery. It provides a simple integration method that allows Java applications to register with Eureka Server as Eureka Clients and discover other services through Eureka Clients.
3. Complete sample:
Firstly, start an Eureka Server. Add the following configuration to the 'application. properties' file:
properties
server.port=8761
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
Then, create a service provider. Add the following dependencies in 'pom. xml':
<dependencies>
<!-- Eureka Client -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
</dependencies>
Add the following configuration to the 'application. properties' file:
properties
server.port=8081
# Eureka Client
eureka.client.service-url.default-zone=http://localhost:8761/eureka/
Add the annotation '@ enableEurekaClient' on the startup class:
@SpringBootApplication
@EnableEurekaClient
public class ServiceProviderApplication {
public static void main(String[] args) {
SpringApplication.run(ServiceProviderApplication.class, args);
}
}
Next, create a service consumer. Add the following dependencies in 'pom. xml':
<dependencies>
<!-- Eureka Client -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
</dependencies>
Add the following configuration to the 'application. properties' file:
properties
server.port=8082
# Eureka Client
eureka.client.service-url.default-zone=http://localhost:8761/eureka/
Add the annotation '@ enableEurekaClient' on the startup class:
@SpringBootApplication
@EnableEurekaClient
public class ServiceConsumerApplication {
public static void main(String[] args) {
SpringApplication.run(ServiceConsumerApplication.class, args);
}
}
Finally, invoke the interface of the service provider through the service consumer. Create a 'HelloController' and inject an instance of the service provider into it:
@RestController
public class HelloController {
@Autowired
private RestTemplate restTemplate;
@GetMapping("/hello")
public String hello() {
ResponseEntity<String> responseEntity = restTemplate.getForEntity("http://service-provider/hello", String.class);
return responseEntity.getBody();
}
}
Inject an instance of 'RestTemplate' on the startup class:
@Configuration
public class RestTemplateConfig {
@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
4. Summary:
By using the 'spring cloud starter netflix eureka client' dependency, we can easily achieve client load balancing in Java applications. Firstly, we need to start an Eureka Server and then create service providers and service consumers. In service consumers, we use 'RestTemplate' to inject instances of service providers and achieve load balancing by calling their interfaces.
