Ribbon service call

# 1. Introducing dependencies into a project
- explain : 
    1. If you are using eureka client and consul client, There is no need to introduce dependencies , Because in eureka,consul Integrated by default in ribbon Components
    2. If used client There is no ribbon Dependencies need to explicitly introduce the following dependencies

<!-- introduce ribbon rely on -->
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>

# 2. see consul client Depending on ribbon

# 3. Use restTemplate + ribbon Make service calls 
-  Use discovery client   Make client calls 
-  Use loadBalanceClient  Make client calls 
-  Use @loadBalanced      Make client calls 

# 3.1  Use discovery Client Form call 

@Autowired
private DiscoveryClient discoveryClient;

// Get a list of services 
List<ServiceInstance> products = discoveryClient.getInstances(" service ID");
for (ServiceInstance product : products) {
  log.info(" Service host :[{}]",product.getHost());
  log.info(" Service port :[{}]",product.getPort());
  log.info(" Service address :[{}]",product.getUri());
  log.info("====================================");
}

# 3.2  Use loadBalance Client Form call 

@Autowired
private LoadBalancerClient loadBalancerClient;
// Select a service call according to the load balancing strategy 
ServiceInstance product = loadBalancerClient.choose(" service ID");
log.info(" Service host :[{}]",product.getHost());
log.info(" Service port :[{}]",product.getPort());
log.info(" Service address :[{}]",product.getUri());

# 3.3  Use @loadBalanced

//1. Integrate restTemplate + ribbon
@Bean
@LoadBalanced
public RestTemplate getRestTemplate(){
  return new RestTemplate();
}
//2. Call service location injection RestTemplate
@Autowired
private RestTemplate restTemplate;
//3. call 
String forObject = restTemplate.getForObject("http:// service ID/hello/hello?name=" + name, String.class);