<dependency>
    <groupld>org.springframework.cloud</groupld>
    <artifactld>spring-cloud-starter-netflix-ribbon</artifactid>
</dependency>

    @GetMapping("/consumer/payment/getForEntity/{id}")
    public CommonResult<Payment> getPayment2(@PathVariable("id") Long id){
        ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL + "/payment/get", CommonResult.class);

        if(entity.getStatusCode().is2xxSuccessful()){
            return entity.getBody();
        }else {
            return new CommonResult<>(444,"操作失败");
        }
    }

@Configuration
public class MySelfRule {

    @Bean
    public IRule myRule(){
        return new RandomRule();
    }
}

@SpringBootApplication
@EnableEurekaClient
@RibbonClient(name = "CLOUD-PAYMENT-SERVICE",configuration = MySelfRule.class)
public class OrderMain80 {
    public static void main(String[] args) {
        SpringApplication.run(OrderMain80.class,args);
    }
}

package com.netflix.loadbalancer;

public interface IRule {
    Server choose(Object var1);

    void setLoadBalancer(ILoadBalancer var1);

    ILoadBalancer getLoadBalancer();
}

package com.netflix.loadbalancer;

import com.netflix.client.config.IClientConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * The most well known and basic load balancing strategy, i.e. Round Robin Rule.
 *
 * @author stonse
 * @author Nikos Michalakis <nikos@netflix.com>
 *
 */
public class RoundRobinRule extends AbstractLoadBalancerRule {

    private AtomicInteger nextServerCyclicCounter;
    private static final boolean AVAILABLE_ONLY_SERVERS = true;
    private static final boolean ALL_SERVERS = false;

    private static Logger log = LoggerFactory.getLogger(RoundRobinRule.class);

    public RoundRobinRule() {
        nextServerCyclicCounter = new AtomicInteger(0);
    }

    public RoundRobinRule(ILoadBalancer lb) {
        this();
        setLoadBalancer(lb);
    }

    //重点关注这方法。
    public Server choose(ILoadBalancer lb, Object key) {
        if (lb == null) {
            log.warn("no load balancer");
            return null;
        }

        Server server = null;
        int count = 0;
        while (server == null && count++ < 10) {
            List<Server> reachableServers = lb.getReachableServers();
            List<Server> allServers = lb.getAllServers();
            int upCount = reachableServers.size();
            int serverCount = allServers.size();//2

            if ((upCount == 0) || (serverCount == 0)) {
                log.warn("No up servers available from load balancer: " + lb);
                return null;
            }

            int nextServerIndex = incrementAndGetModulo(serverCount);//下标位置
            server = allServers.get(nextServerIndex);//0 1 0 1 0 1...

            if (server == null) {
                /* Transient. */
                Thread.yield();
                continue;
            }

            if (server.isAlive() && (server.isReadyToServe())) {
                return (server);
            }

            // Next.
            server = null;
        }

        if (count >= 10) {
            log.warn("No available alive servers after 10 tries from load balancer: "
                    + lb);
        }
        return server;
    }

    /**
     * Inspired by the implementation of {@link AtomicInteger#incrementAndGet()}.
     *
     * @param modulo The modulo to bound the value of the counter.
     * @return The next value.
     */
    private int incrementAndGetModulo(int modulo) {
        for (;;) {
            int current = nextServerCyclicCounter.get();
            int next = (current + 1) % modulo;//求余法
            if (nextServerCyclicCounter.compareAndSet(current, next))//比较并交换
                return next;
        }
    }

    @Override
    public Server choose(Object key) {
        return choose(getLoadBalancer(), key);
    }

    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig) {
    }
}

@RestController
@Slf4j
public class PaymentController{

    ...
    
	@GetMapping(value = "/payment/lb")
    public String getPaymentLB() {
        return serverPort;//返回服务接口
    }
    
    ...
}

/**
 * @author frx
 * @version 1.0
 * @date 2022/8/16  0:55
 desc:收集现在服务器集群上总共有多少台能够提供服务的机器，放到List里面
 */
public interface LoadBalancer {

    ServiceInstance instances(List<ServiceInstance> serviceInstance);

}

/**
 * @author frx
 * @version 1.0
 * @date 2022/8/16  0:58
 */
@Component
public class MyLB implements LoadBalancer {

    private AtomicInteger atomicInteger = new AtomicInteger(0);//初始值为0

    public final int getAndIncrement(){
        int current;
        int next;
        do{
            current = this.atomicInteger.get();//得到初始值
            next = current >= 2147483647 ? 0 : current + 1;
        //比较，如果当前值current与期望值一致，就修改 返回true 取反 跳出循环
        }while (!this.atomicInteger.compareAndSet(current,next));
        System.out.println("-----第几次访问，次数next-----:"+next);//
        return next;
    }

    @Override
    public ServiceInstance instances(List<ServiceInstance> serviceInstance) {

        int index = getAndIncrement() % serviceInstance.size();
        return serviceInstance.get(index);
    }
}

@RestController
@Slf4j
public class OrderController {

    //public static final String PAYMENT_URL= "http://localhost:8001";
    public static final String PAYMENT_URL = "http://CLOUD-PAYMENT-SERVICE";//eureka注册的服务名称
	
    //...

    @Resource
    private LoadBalancer loadBalancer;

    @Resource
    private DiscoveryClient discoveryClient;    
	@GetMapping(value = "/consumer/payment/lb")
    public String getPaymentLB(){
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        if(instances == null || instances.size() <= 0){
            return null;
        }
        ServiceInstance serviceInstance = loadBalancer.instances(instances);
        URI uri = serviceInstance.getUri();
        return restTemplate.getForObject(uri+"/payment/lb",String.class);
    }
    
    //...
}