SpringCloud - Spring Cloud Alibaba 之 Nacos Discovery服务注册发现（三）

川长思鸟来 2023-09-28 13:43 141阅读 0赞

#### 阅读本文可先参考博文 ####

[https://blog.csdn.net/MinggeQingchun/article/details/125613600][https_blog.csdn.net_MinggeQingchun_article_details_125613600]

[https://blog.csdn.net/MinggeQingchun/article/details/125614065][https_blog.csdn.net_MinggeQingchun_article_details_125614065]

## 一、Nacos Discovery服务注册发现 ##

#### 1、服务提供者 ####

1、创建一个spring boot 模块 springcloud-alibaba-1-nacos-discovery-provider

2、添加 spring-cloud-starter-alibaba-nacos-discovery 等依赖

（1）通过添加一个starter依赖：spring-cloud-starter-alibaba-nacos-discovery它通过自动配置、注解以及Spring Boot 编程模型与Nacos无缝集成，实现服务注册与发现

<dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-actuator</artifactId>
            </dependency>

（2）Spring Cloud Alibaba 和 Spring Cloud，Spring Boot对应版本

在该工程的 pom.xml 中，我们通过 dependencyManagement 对 Spring Cloud Alibaba 的版本信息进行管理，该工程下的各个子模块在引入 Spring Cloud Alibaba 的各个组件时就不要单独指定版本号了

<properties>
            <java.version>1.8</java.version>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <spring-boot.version>2.3.12.RELEASE</spring-boot.version>
            <spring-cloud-alibaba.version>2.2.7.RELEASE</spring-cloud-alibaba.version>
    </properties>
    
    
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>com.alibaba.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>${spring-cloud-alibaba.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Hoxton.SR12</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-dependencies</artifactId>
                    <version>${spring-boot.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>

完整POM文件如下

<modelVersion>4.0.0</modelVersion>
    
        <groupId>com.company</groupId>
        <artifactId>springcloud-alibaba-1-nacos-discovery-provider</artifactId>
        <version>1.0.0</version>
    
        <name>springcloud-alibaba-1-nacos-discovery-provider</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <spring-boot.version>2.3.12.RELEASE</spring-boot.version>
            <spring-cloud-alibaba.version>2.2.7.RELEASE</spring-cloud-alibaba.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>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-actuator</artifactId>
            </dependency>
    
            <dependency>
                <groupId>com.company</groupId>
                <artifactId>springcloud-alibaba-1-commons</artifactId>
                <version>1.0.0</version>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-devtools</artifactId>
                <optional>true</optional>
            </dependency>
    
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>2.2.2</version>
            </dependency>
    
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
            </dependency>
    
        </dependencies>
    
        
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>com.alibaba.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>${spring-cloud-alibaba.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Hoxton.SR12</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-dependencies</artifactId>
                    <version>${spring-boot.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                        <encoding>UTF-8</encoding>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
                
                <plugin>
                    <groupId>org.mybatis.generator</groupId>
                    <artifactId>mybatis-generator-maven-plugin</artifactId>
                    <version>1.4.0</version>
                    <configuration>
                        
                        <configurationFile>src/main/resources/generatorConfig.xml</configurationFile>
                        
                        <verbose>true</verbose>
                        
                        <overwrite>true</overwrite>
                    </configuration>
                </plugin>
            </plugins>
    
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.xml</include>
                    </includes>
                </resource>
                <resource>
                    <directory>src/main/resources</directory>
                    <includes>
                        <include>**/*.*</include>
                    </includes>
                </resource>
            </resources>
        </build>

3、 在应用的/src/main/resources/application.properties(也可以是application.yaml) 配置文件中配置 Nacos Server 地址，如果不想使用Nacos作为您的服务注册与发现，可以将 spring.cloud.nacos.discovery.enabled 设置为 false

#内嵌的web服务器端口
    server.port=9001
    
    #服务名称
    spring.application.name=springcloud-alibaba-1-nacos-discovery-provider
    
    #设置mysql数据库连接信息
    spring.datasource.url=jdbc:mysql://localhost:3306/springcloud?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT%2B8
    spring.datasource.username=root
    spring.datasource.password=admin123456
    
    #将Nacos设置为服务注册发现，默认为true
    spring.cloud.nacos.discovery.enabled=true
    #nacos注册中心的连接地址
    spring.cloud.nacos.discovery.server-addr=192.168.133.129:8848
    
    #nacos的用户名和密码
    spring.cloud.nacos.username=nacos
    spring.cloud.nacos.password=nacos
    
    #spring boot actuator 监控和健康检查功能
    management.endpoints.jmx.exposure.include=*
    management.endpoints.web.exposure.include=*
    management.endpoint.health.show-details=always

4、在Spring Boot启动类加上 **@EnableDiscoveryClient** 注解

@EnableDiscoveryClient //开启服务注册与发现功能： classpath: META-INF/spring.factories文件
    @SpringBootApplication
    public class Alibaba1NacosDiscoveryProviderApplication {
        public static void main(String[] args) {
            SpringApplication.run(Alibaba1NacosDiscoveryProviderApplication.class, args);
        }
    }

![e20f98a20cd14d66ab9535318eaf2db8.png][]

5、编写controller测试类

@Slf4j
    @RestController
    public class EchoController {
    
        @GetMapping("/")
        public ResponseEntity index() {
            log.info("provider /");
            return new ResponseEntity("index", HttpStatus.OK);
        }
    
    
        @GetMapping("/divide")
        public String divide(@RequestParam Integer a, @RequestParam Integer b) {
            log.info("provider /divide");
            return String.valueOf(a / b);
        }
    
        @GetMapping("/notFound")
        public String notFound() {
            System.out.println("provider 1 .........");
            return "notFound";
        }
    }

6、启动Nacos服务，启动main类，在nacos服务台上查看服务

![3995bc7d164c4cceaf40217bc8eb9b6c.png][]

点击详情查看![344d5340ac3a451886520e28f454bf6e.png][]

#### 2、服务消费者 ####

1、新建服务消费者 模块 springcloud-alibaba-1-nacos-discovery-consumer

2、添加spring-cloud-starter-alibaba-nacos-discovery，spring-cloud-loadbalancer等

依赖

<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.boot</groupId>
                <artifactId>spring-boot-starter-actuator</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-loadbalancer</artifactId>
            </dependency>

注：

由于 Netflix Ribbon 在2020版 进入停更维护阶段，因此新版本的 Nacos discovery 都已经移除了 Ribbon ， 此时我们需要引入 loadbalancer 代替，才能调用服务提供者提供的服务

<groupId>com.company</groupId>
        <artifactId>springcloud-alibaba-1-nacos-discovery-consumer</artifactId>
        <version>1.0.0</version>
    
        <name>springcloud-alibaba-1-nacos-discovery-consumer</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <spring-boot.version>2.3.12.RELEASE</spring-boot.version>
            <spring-cloud-alibaba.version>2.2.7.RELEASE</spring-cloud-alibaba.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>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-actuator</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-loadbalancer</artifactId>
            </dependency>
    
            <dependency>
                <groupId>com.company</groupId>
                <artifactId>springcloud-alibaba-1-commons</artifactId>
                <version>1.0.0</version>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
                <exclusions>
                    <exclusion>
                        <groupId>org.junit.vintage</groupId>
                        <artifactId>junit-vintage-engine</artifactId>
                    </exclusion>
                </exclusions>
            </dependency>
    
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
            </dependency>
        </dependencies>
    
        
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>com.alibaba.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>${spring-cloud-alibaba.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Hoxton.SR12</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-dependencies</artifactId>
                    <version>${spring-boot.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                        <encoding>UTF-8</encoding>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
    
            </plugins>
        </build>

#内嵌的web服务器端口
    server.port=8081
    
    #服务名称
    spring.application.name=springcloud-alibaba-1-nacos-discovery-consumer
    
    #将Nacos设置为服务注册发现，默认为true
    spring.cloud.nacos.discovery.enabled=true
    #nacos注册中心的连接地址
    spring.cloud.nacos.discovery.server-addr=192.168.133.129:8848
    
    #nacos的用户名和密码
    spring.cloud.nacos.username=nacos
    spring.cloud.nacos.password=nacos
    
    #spring boot actuator 监控和健康检查功能
    management.endpoints.jmx.exposure.include=*
    management.endpoints.web.exposure.include=*
    management.endpoint.health.show-details=always
    
    #自定义配置，远程服务提供者的服务名
    service.name=http://springcloud-alibaba-1-nacos-discovery-provider
    
    #避免The bean 'springcloud-alibaba-1-nacos-discovery-provider.FeignClientSpecification' could not be registered. A bean with that name has already been defined and overriding is disabled.
    spring.main.allow-bean-definition-overriding=true

注：

springboot bean覆盖注册的问题 **allowBeanDefinitionOverriding** 配置

项目引用三方jar包，需要对@Configuration配置类中的某个bean进行重写。过程中遇到了bean已被注册异常、以及新加的bean不加载

***************************
    APPLICATION FAILED TO START
    ***************************
    
    Description:
    
    The bean 'springcloud-alibaba-1-nacos-discovery-provider.FeignClientSpecification' could not be registered. A bean with that name has already been defined and overriding is disabled.
    
    Action:
    
    Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true
    
    Disconnected from the target VM, address: '127.0.0.1:56743', transport: 'socket'

![5a2278f6956940eda9a9cb374d6d1701.png][] 在项目中定义了两个 Feign 客户端 ，两个 Feign 客户端中配置的 value 值是一样的 导致在启动时报如上错误

设置 spring.main.allow-bean-definition-overriding=true 即可

4、 在Spring Boot启动类加上 **@EnableDiscoveryClient** 注解

@EnableFeignClients //开启feign
    @EnableDiscoveryClient //开启nacos服务注册与发现
    @SpringBootApplication
    public class Alibaba1NacosDiscoveryConsumerApplication {
        public static void main(String[] args) {
            SpringApplication.run(Alibaba1NacosDiscoveryConsumerApplication.class, args);
        }
    }

5、 编写测试类controller

@RestController
    public class TestController {
    
    	@Autowired
    	private LoadBalancerClient loadBalancerClient;
    
    	@Autowired
    	private RestTemplate restTemplate;
    
    	//feign 的声明式调用
    	@Autowired
    	private EchoFeignService echoFeignService;
    
    	@Autowired
    	private DiscoveryClient discoveryClient;
    
    	@GetMapping("/echo/{app}")
    	public String echoAppName(@PathVariable("app") String app){
    		//使用 LoadBalanceClient 和 RestTemplate 结合的方式来访问
    		ServiceInstance serviceInstance = loadBalancerClient.choose("springcloud-alibaba-1-nacos-discovery-provider");
    
    		//  http://192.168.0.104:18082/echo/{app}
    		String url = String.format("http://%s:%s/echo/%s", serviceInstance.getHost(), serviceInstance.getPort(), app);
    		System.out.println("request url:"+url);
    
    		return restTemplate.getForObject(url, String.class);
    	}
    
    
    	@GetMapping("/notFound-feign")
    	public String notFound() {
    		return echoFeignService.notFound();
    	}
    
    	@GetMapping("/divide-feign")
    	public String divide(@RequestParam Integer a, @RequestParam Integer b) {
    		return echoFeignService.divide(a, b);
    	}
    
    	@GetMapping("/divide-feign2")
    	public String divide(@RequestParam Integer a) {
    		return echoFeignService.divide(a);
    	}
    
    	@GetMapping("/echo-feign/{str}")
    	public String feign(@PathVariable String str) {
    		return echoFeignService.echo(str);
    	}
    
    	@GetMapping("/services/{service}")
    	public Object client(@PathVariable String service) {
    		return discoveryClient.getInstances(service);
    	}
    
    	@GetMapping("/services")
    	public Object services() {
    		System.out.println(discoveryClient.description());
    		System.out.println(discoveryClient.getOrder());
    		return discoveryClient.getServices();
    	}
    }

@Configuration
    public class MyRibbonConfig {
    
    //    @SentinelRestTemplate(/*blockHandler="blockA", blockHandlerClass= MyBlockHandlerClass.class*/ //限流
    //            fallback="fallbackA", fallbackClass = MyBlockHandlerClass.class) // 降级
        @Bean
        @LoadBalanced //与 Ribbon 集成，并开启负载均衡功能
        public RestTemplate restTemplate() {
            return new RestTemplate();
        }
    }

EchoFeignService

@FeignClient(name = "springcloud-alibaba-1-nacos-discovery-provider",
            fallbackFactory = EchoFeignServiceFallbackFactory.class,
            configuration = FeignConfiguration.class)
    public interface EchoFeignService {
    
        @GetMapping("/echo/hello")
        default String hello() {
            return "hello";
        }
    
        @GetMapping("/echo/{str}")
        String echo(@PathVariable("str") String str);
    
        @GetMapping("/divide")
        String divide(@RequestParam("a") Integer a, @RequestParam("b") Integer b);
    
        /**
         * feign声明的接口可以有默认实现， 就是可以不需要远程服务提供者实现，自己实现了
         *
         * @param a
         * @return
         */
        default String divide(Integer a) {
            System.out.println("consumer devide method......");
            return divide(a, 1);
        }
    
        // restTemplate.getForObject("http://springcloud-alibaba-1-nacos-discovery-provider/sleep", String.class);
    
        // @FeignClient(name = "springcloud-alibaba-1-nacos-discovery-provider")
        // http://springcloud-alibaba-1-nacos-discovery-provider/notFound
    
        @GetMapping("/notFound")
        String notFound();
    }

EchoFeignServiceFallbackFactory

public class EchoFeignServiceFallbackFactory implements FallbackFactory<EchoFeignService> {
    
        @Override
        public EchoFeignService create(Throwable throwable) {
            return new EchoFeignService() {
                @Override
                public String hello() {
                    return "hello fall back" + throwable.getMessage();
                }
    
                @Override
                public String echo(@PathVariable("str") String str) {
                    return "echo fallback" + throwable.getMessage();
                }
    
                @Override
                public String divide(@RequestParam Integer a, @RequestParam Integer b) {
                    return "divide fallback" + throwable.getMessage();
                }
    
                @Override
                public String divide(Integer a) {
                    return "divide fall back" + throwable.getMessage();
                }
    
                @Override
                public String notFound() {
                    return "default feign invoke notFound fallback 999" + throwable.getMessage();
                }
            };
        }
    }

FeignConfiguration

public class FeignConfiguration {
    
        @Bean
        public EchoFeignServiceFallbackFactory echoFeignServiceFallbackFactory() {
            return new EchoFeignServiceFallbackFactory();
        }
    }

6、启动Nacos服务，启动main类，在nacos服务台上查看服务

[http://localhost:8081/divide-feign?a=10&b=2][http_localhost_8081_divide-feign_a_10_b_2]

![a1cf6a08bbc54062a18999926cc9661b.png][]

![5983f26ae6534a4d9918dac24149b12d.png][]

注：

**`Nacos注册中心宕机，不影响已运行的提供者和消费者，消费者在本地缓存了提供者列表`**

[https_blog.csdn.net_MinggeQingchun_article_details_125613600]: https://blog.csdn.net/MinggeQingchun/article/details/125613600
[https_blog.csdn.net_MinggeQingchun_article_details_125614065]: https://blog.csdn.net/MinggeQingchun/article/details/125614065
[e20f98a20cd14d66ab9535318eaf2db8.png]: https://img-blog.csdnimg.cn/e20f98a20cd14d66ab9535318eaf2db8.png
[3995bc7d164c4cceaf40217bc8eb9b6c.png]: https://img-blog.csdnimg.cn/3995bc7d164c4cceaf40217bc8eb9b6c.png
[344d5340ac3a451886520e28f454bf6e.png]: https://img-blog.csdnimg.cn/344d5340ac3a451886520e28f454bf6e.png
[5a2278f6956940eda9a9cb374d6d1701.png]: https://img-blog.csdnimg.cn/5a2278f6956940eda9a9cb374d6d1701.png
[http_localhost_8081_divide-feign_a_10_b_2]: http://localhost:8081/divide-feign?a=10&b=2
[a1cf6a08bbc54062a18999926cc9661b.png]: https://img-blog.csdnimg.cn/a1cf6a08bbc54062a18999926cc9661b.png
[5983f26ae6534a4d9918dac24149b12d.png]: https://img-blog.csdnimg.cn/5983f26ae6534a4d9918dac24149b12d.png