1、添加依赖

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

完整pom.xml文件

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.shenmazong</groupId>
    <artifactId>cloud-nacos-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>cloud-nacos-consumer</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <!-- 设置SpringCloud的版本 -->
        <spring-cloud.version>Hoxton.SR2</spring-cloud.version>
    </properties>
    <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>
            <version>2.2.2.RELEASE</version>
        </dependency>

        <!-- 增加openfeign依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <!-- 增加SpringClud的库依赖 -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

2、定义接口

package com.shenmazong.cloudnacosconsumer.service;

import com.shenmazong.cloudnacosconsumer.service.impl.ConsumerServiceImpl;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient(name = "cloud-nacos-provider",fallback = ConsumerServiceImpl.class)
public interface ConsumerService {

    @RequestMapping(value = "/echo/{str}", method = RequestMethod.GET)
    String echo(@PathVariable String str);
}

3、定义熔断函数

package com.shenmazong.cloudnacosconsumer.service.impl;

import com.shenmazong.cloudnacosconsumer.service.ConsumerService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

/**
 * @author 军哥
 * @version 1.0
 * @description: 消费者的熔断类
 * @date 2021/8/20 15:59
 */

@Component
@Slf4j
public class ConsumerServiceImpl implements ConsumerService {
    @Override
    public String echo(String str) {
        log.info("-- echo 熔断了 --");
        return "echo 熔断了";
    }
}

4、定义接口

package com.shenmazong.cloudnacosconsumer.controller;

import com.shenmazong.cloudnacosconsumer.service.ConsumerService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;

/**
 * @author 军哥
 * @version 1.0
 * @description: TODO
 * @date 2021/8/19 11:31
 */

@RestController
@Slf4j
public class IndexController {

    @Autowired
    private ConsumerService consumerService;

    @GetMapping(value = "/openMessage/{str}")
    public String openMessage(@PathVariable String str) {
        log.info("openMessage:str="+str);
        return consumerService.echo(str);
    }
}

5、启动类加注解

package com.shenmazong.cloudnacosconsumer;

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(basePackages = "com.shenmazong.cloudnacosconsumer.service.*")
public class CloudNacosConsumerApplication {

    public static void main(String[] args) {
        SpringApplication.run(CloudNacosConsumerApplication.class, args);
    }
}

6、测试运行