【SpringCloud】07. Communication between applications

Inter application communication

HTTP vs RPC

1. Two restful invocation methods between services in spring cloud

Method 1: resttemplate: an HTTP client

There are three ways to resttemplate

1. Write URL directly: http://localhost:8080/msg

Use resttemplate getForObject(" http://localhost:8080/msg ", string. Class); method

@RestController
@Slf4j
public class ClientController {
    @GetMapping("/getProductMsg")
    public String getProductMsg(){
        //1. 第一种方式
        RestTemplate restTemplate = new RestTemplate();
        String response = restTemplate.getForObject("http://localhost:8080/msg",String.class);
        log.info("response={}",response);
        return response;
    }
}

Disadvantages: the address is dead. If the other party has more than one service, it's very bad.

2. Through serviceinstance, serviceinstance = loadbalancerclient choose("ServerId"); Get information about the service. Serverid: name of the service

  @Autowired
  private LoadBalancerClient loadBalancerClient;

@RestController
@Slf4j
public class ClientController {
    @Autowired
    private LoadBalancerClient loadBalancerClient;
    
    @GetMapping("/getProductMsg")
    public String getProductMsg(){
        //2.第二种
        ServiceInstance serviceInstance= loadBalancerClient.choose("PRODUCT");
        String url = String.format("http://%s:%s",serviceInstance.getHost(),serviceInstance.getPort())+"/msg";
        RestTemplate restTemplate = new RestTemplate();
        String response = restTemplate.getForObject(url,response);
        return response;
    }

Advantages: we can not know the service path, but use the service ID or service path information. Disadvantages: the coding is cumbersome

3. Use @ loadbalanced to access the application name in resttemplate

@Component
public class RestTemplateConfig {
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }
}

@RestController
@Slf4j
public class ClientController {
    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/getProductMsg")
    public String getProductMsg(){
        //3.第三种方式 利用@LoadBalanced 可在restTemplate里使用应用名字
        String response = restTemplate.getForObject("http://PRODUCT/msg",response);
        return response;
    }
}