一、加依赖：

<?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"><modelVersion>4.0.0</modelVersion><groupId>cn.edu.tju</groupId><artifactId>springbootcircuitbreaker</artifactId><version>1.0-SNAPSHOT</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.6.6</version></parent><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>2021.0.1</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-dependencies</artifactId><version>2021.0.1.0</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-sentinel</artifactId></dependency><dependency><groupId>com.alibaba.csp</groupId><artifactId>sentinel-datasource-nacos</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-bootstrap</artifactId></dependency><dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>30.0-jre</version></dependency><dependency><groupId>com.google.code.gson</groupId><artifactId>gson</artifactId><version>2.8.6</version></dependency></dependencies></project>

二、配置文件启用feign对sentinel的支持：

feign:sentinel:enabled: true

三、定义被调用的接口：

package cn.edu.tju.controller;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
public class StockController {@RequestMapping("/getStock")public String getStock(){int t = 1 / 0;return "getStock";}
}

四、定义FeignClient及降级类：

package cn.edu.tju.service;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;@FeignClient(value = "circuit-breaker", fallback = MyFallbackService.class)
public interface StockService {@RequestMapping("/getStock")String getStock();
}

package cn.edu.tju.service;import org.springframework.stereotype.Component;@Component
public class MyFallbackService implements StockService{@Overridepublic String getStock() {return "degraded get stock";}
}

五、定义controller，注入@FeignClient

package cn.edu.tju.controller;import cn.edu.tju.service.StockService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
public class DegradeController {@Autowiredprivate StockService stockService;@RequestMapping("/getDegrade")public String getDegrade(){return stockService.getStock();}
}

六、接口调用结果：