Feign元件一般是消費側

1.POM中增加openfeign引入

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springcloud-nacos</artifactId>
        <groupId>com.ckfuture.springcloud</groupId>
        <version>1.0
 
-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>cloudalibaba-consumer-nacos-order84</artifactId>

    <dependencies>
        <!--SpringCloud alibaba nacos-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!--SpringCloud alibaba sentinel-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
        </dependency>
        <!--SpringCloud openfeign-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--web+actuator-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>

</project>

2.YML中啟用Sentinel對Feign的支援

server:
  port: 84
spring:
  application:
    name: nacos-order-consumer
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
    sentinel:
      transport:
        #配置Sentinel dashboard地址
        dashboard: localhost:8080
        port: 8719

#消費者將要去訪問的微服務名稱（註冊成功進nacos的微服務提供者）
service
 
-url:
  nacos-user-service: http://nacos-payment-provider
#啟用Sentinel 對Feign的支援
feign:
  sentinel:
    enabled: true

3.主啟動類啟用@EnableFeignClients

package com.ckfuture.springcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class OrderNacosMain84 {
    public static void main(String[] args) {
        SpringApplication.run(OrderNacosMain84.class,args);
    }
}

 4.新建帶@FeignClient註解的業務介面

Feign就是介面+註解

介面中方法呼叫地址要和生產者中的呼叫地址一樣。參考Feign呼叫方式

package com.ckfuture.springcloud.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

/**
 * @author ckfuture
 */
@FeignClient(value = "nacos-payment-provider")
public interface PaymentService {

    @GetMapping(value = "/payment/nacos/{id}")
    public String getPayment(@PathVariable("id") Integer id);

}

 5.建立Feign兜底類

建立名為“PaymentFallbackService”的類，實現PaymentService介面方法

package com.ckfuture.springcloud.service;

import org.springframework.stereotype.Component;

/**
 * Feign
 * 兜底類
 */
@Component
public class PaymentFallbackService implements PaymentService{
    @Override
    public String getPayment(Integer id) {
        return "服務降級返回，---PaymentFallbackService";
    }
}

6.介面中新增fallback（兜底）方法

package com.ckfuture.springcloud.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

/**
 * @author ckfuture
 */
@FeignClient(value = "nacos-payment-provider",fallback = PaymentFallbackService.class)
public interface PaymentService {

    @GetMapping(value = "/payment/nacos/{id}")
    public String getPayment(@PathVariable("id") Integer id);
}

7.新增controller方法

  //=============OpenFeign============
    @Resource
    private PaymentService paymentService;

    @GetMapping(value = "/consumer/payment/nacos/{id}")
    public String getPayment(@PathVariable("id") Integer id){
        return paymentService.getPayment(id);
    }

8.測試

啟動9001生產者微服務，在Nacos中檢視。

 啟動84埠的消費者，在Nacos中檢視

 此時故意關閉9001埠微服務，再次請求檢視效果。