三种远程调用的方法

需要的依赖

<!--        服务发现-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
<!--        远程调用-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
<!--        负载均衡-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>

方法一

 discoveryClient.getInstances("service-product")

    @Autowired
    private DiscoveryClient discoveryClient;

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private LoadBalancerClient loadBalancerClient; 

public Product getProductFromRemote(Integer productId) {
// : 调用商品服务所在的所有机器的ip端口 service-product 是对应的服务名
        List<ServiceInstance> instances = discoveryClient.getInstances("service-product");
//这里选择的是第一个instances.get(0)
        ServiceInstance serviceInstance = instances.get(0);
        String host = serviceInstance.getHost();
        int port = serviceInstance.getPort();
        String url = "http://" + host + ":" + port + "/getProduct/" + productId;
        log.info("发送请求，请求地址：{}", url);
        Product product = restTemplate.getForObject(url, Product.class);
        return product;
    }

方法二

loadBalancerClient.choose("service-product");

    @Autowired
    private DiscoveryClient discoveryClient;

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private LoadBalancerClient loadBalancerClient;
// 使用负载均衡发送
    public Product getProductFromRemoteWithLoadBalancer(Integer productId) {
        ServiceInstance choose = loadBalancerClient.choose("service-product");
        String host = choose.getHost();
        int port = choose.getPort();
        String url = "http://" + host + ":" + port + "/getProduct/" + productId;
//        TODO: 发送请求
        log.info("发送请求，请求地址：{}", url);
        Product product = restTemplate.getForObject(url, Product.class);
        return product;
    }

方法三基于注解

@Configuration
public class OrderServiceConfig {
    @LoadBalanced //仅仅通过一个注解开启负载均衡
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

    // 基于注解的方式实现负载均衡
    public Product getProductAnnocation(Integer productId) {
        String url = "http://service-product/getProduct/" + productId;
        // service-product 是服务名,会自动去注册中心获取服务的ip和端口
        log.info("基于注解，请求地址：{}", url);
        Product product = restTemplate.getForObject(url, Product.class);
        return product;
    }