Three ways to call other microservices
1. Rest method (underlying Httpclient tool)
@SuppressWarnings("unchecked")
@Service
public class MemberService {
@Autowired
RestTemplate restTemplate;
public List<String> getOrderByUserList() {
return restTemplate.getForObject("http://service-member/getUserList",
List.class);//Return value.class
}
}
2. Ribbon method (underlying Httpclient tool)
In the startup class of the project, register with the service center through @EnableDiscoveryClient; and inject a bean: restTemplate into the ioc of the program; and use the @LoadBalanced annotation to indicate that this restRemplate enables load balancing. Use load balancing strategy to rotate to call service interface
@EnableEurekaClient
@SpringBootApplication
public class AppOrder {
public static void main(String[] args) {
SpringApplication.run(AppOrder.class, args);
}
@Bean
@LoadBalanced
RestTemplate restTemplate() {
return new RestTemplate();
}
}
2. Feign method (underlying Httpclient tool) feignClient has used the ribbon's own load balancing by default
Startup class @Enable FeignClients
fegin code
@FeignClient(value="service-member",fallback=MemberFeignService.class)
public interface MemberFeign {
@RequestMapping("/getMemberAll")
public List<String> getOrderByUserList(); //Write the method name as you like
}
* 1、这里需要设置请求的方式为 RequestMapping 注解，用 GetMapping 注解是运行不成功的，即 GetMapping 不支持。
*
* 2、注解 PathVariable 里面需要填充变量的名字，不然也是运行不成功的。 如果入参是一个对象的话，那么这个方法在 feign 里面默认为 POST 方法，就算你写成 GET 方式也无济于事。 首先通过@EnableFeignCleints注解开启FeignCleint
根据Feign的规则实现接口，并加@FeignCleint注解
程序启动后，会进行包扫描，扫描所有的@ FeignCleint的注解的类，并将这些信息注入到ioc容器中。
当接口的方法被调用，通过jdk的代理，来生成具体的RequesTemplate
RequesTemplate在生成Request
Request交给Client去处理，其中Client可以是HttpUrlConnection、HttpClient也可以是Okhttp
最后Client被封装到LoadBalanceClient类，这个类结合类Ribbon做到了负载均衡。