SpringCloud------使用Ribbon负载均衡

1.添加依赖

<dependency>
　　<groupId>org.springframework.boot</groupId>
　　<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
　　<groupId>org.springframework.cloud</groupId>
　　<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
　　<dependency>
　　<groupId>org.springframework.cloud</groupId>
　　<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>

<!-- lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

2.修改启动类

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@MapperScan("cn.ytheng.order_service")
public class OrderServiceApplication {

    /**
     * @Loadbalanced负载均衡策略
     */
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    public static void main(String[] args) {

        SpringApplication.run(OrderServiceApplication.class, args);
    }

}

3.添加Controller

import cn.theng.order_service.utils.RibbonUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;
import java.util.Map;

@RestController
@RequestMapping("/api/v1/order")
public class ProductOrderController {

    @RequestMapping("/test")
    public Object test(@RequestParam("product_id") int productId) {

        //方法一
//        ServiceInstance instance = loadBalancerClient.choose("product-service");
//        String url = String.format("http://%s:%s/api/v1/product/find?id=" + productId, instance.getHost(), instance.getPort());
//        RestTemplate template = new RestTemplate();
//        Map<String, Object> map2 = template.getForObject(url, Map.class);

        //负载均衡
        //商品列表启用两个节点时
        //由客户端来自动选择节点，可能是8771端口，也有可能是8772端口
        //参数id名称需要保持一致
        //方法二(推荐)
        String uri = "http://product-service/api/v1/product/find?id={id}";
        Map<String, Object> request = new HashMap<>();
        request.put("id", productId);
        Map<String, Object> map3 = RibbonUtils.get(uri, Map.class, request);

        return "success";
    }

    @PostMapping("/test2")
    public Object test2(@RequestParam("product_id") int productId) {

        Product product = new Product();
        product.setId(productId);

        String uri = "http://product-service/api/v1/product/find2";
        LinkedMultiValueMap<String, String> headers = new LinkedMultiValueMap<>();
        headers.add("token", "theng");
        Object result = RibbonUtils.post(uri, Object.class, product, headers);

        return "success";
    }
}

4.添加Ribbon调用公共类

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.*;
import org.springframework.stereotype.Component;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.web.client.RestTemplate;

import javax.annotation.PostConstruct;
import java.util.Arrays;
import java.util.Collections;
import java.util.Map;

@Component
public class RibbonUtils {

    @Autowired
    private RestTemplate restTemplate;

    private static RestTemplate template;

    //@PostConstruct修饰的方法会在服务器加载Servlet的时候运行，并且只会被服务器调用一次
    @PostConstruct
    public void init() {
        template = restTemplate;
    }

    /**
     *
     * @param uri 接口地址
     * @param responseType 返回类型
     *
     * */
    public static <T> T get(String uri, Class<T> responseType) {

        return template.getForObject(uri, responseType);
    }

    /**
     *
     * @param uri 接口地址
     * @param responseType 返回类型
     * @param request 传递参数
     *
     * */
    public static <T> T get(String uri, Class<T> responseType, Map<String, ?> request) {

        return template.getForObject(uri, responseType, request);
    }

    /**
     *
     * @param uri 接口地址
     * @param responseType 返回类型
     * @param request 传递参数
     * @param headerMap 报头信息
     *
     * */
    public static <T> T get(String uri, Class<T> responseType, Map<String, ?> request, Map<String, String> headerMap) {

        //添加报头
        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));

        for(Map.Entry<String, String> entry : headerMap.entrySet()){
            String mapKey = entry.getKey();
            String mapValue = entry.getValue();
            headers.add(mapKey, mapValue);
        }

        //body的类型定为String,这里使用get没有用到body,post会使用到
        HttpEntity<String> entity = new HttpEntity<String>(null, headers);

        ResponseEntity<T> result = template.exchange(uri, HttpMethod.GET, entity, responseType, request);

        return result.getBody();
    }

    /**
     *
     * @param uri 接口地址
     * @param responseType 返回类型
     * @param body 传递实体
     * @param headers 报头信息
     *
     * */
    public static <T> T post(String uri, Class<T> responseType, Object body, LinkedMultiValueMap<String, String> headers) {

        if (!headers.containsKey("Content-Type")) {
            headers.put("Content-Type", Collections.singletonList("application/json;charset=UTF-8"));
        }

        HttpEntity request = new HttpEntity(body, headers);
        Object obj =  template.postForObject(uri,  request, responseType);
        return (T) obj;
    }
}

5.在PostMan上测试两个接口即可