02-OpenFeign-微服务接入

1、依赖

由于是spring cloud项目，注意spring-boot、cloud、alibaba的版本兼容性

1.1、父级依赖

<properties><java.version>1.8</java.version><spring-boot.version>2.7.18</spring-boot.version><spring.cloud.version>2021.0.1</spring.cloud.version><spring.cloud.alibaba.version>2021.0.1.0</spring.cloud.alibaba.version>
</properties><dependencyManagement><dependencies><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-dependencies</artifactId><version>${spring.cloud.alibaba.version}</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>${spring.cloud.version}</version><type>pom</type><scope>import</scope></dependency><!-- SpringBoot 依赖配置 --><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>

1.2、子服务依赖

<properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><java.version>1.8</java.version>
</properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId><exclusions><exclusion><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-ribbon</artifactId></exclusion></exclusions></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-loadbalancer</artifactId></dependency></dependencies>

以下全部为调用方配置

2、配置项

启动项配置文件 需要在 bootstrap.yml添加如下内容：

server:port: 8090servlet:context-path: /
spring:application:#nacos 注册时的服务名  name: openprofiles:active: seatacloud:nacos:discovery:# nacos的服务地址，nacos-server中IP地址:端口号server-addr: 192.168.20.113:8848# 保持与下游服务一样的域namespace: cedb1f46-d9ae-43b1-99db-39b245152543group: DEFAULT_GROUP

openfeign的负载均衡策略：

- round-robin:轮询

- least-conne¢tion:最小连接数

- consistent-hashing:一致性HASH

或指定URL

@FeignClient(url = "127.0.0.1:9001",name = "async-feign",contextId = "identity")

2.2、添加注解@EnableFeignClients开启openFeign功能

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 OpenFeignConsumer9006Application{public static void main(String[] args) {SpringApplication.run(OpenFeignConsumer9006Application.class, args);}
}

2.3、新建openFeign接口

value作为调用方服务名，可以用final static 常量代替

// 下游服务注册到nacos的服务名
@FeignClient(value = "user-service")
public interface OpenFeignUserService {// 完整的调用地址，如果下游存在/contextPath 则需要补充@GetMapping("/user/save")String insert() ;
}

3、调用错误问题

1、503[Load balancer does not contain an instance for the service ...]

因为SpringCloud Feign在Hoxton.M2 RELEASED版本之后抛弃了Ribbon，

使用了spring-cloud-loadbalancer，所以我们这里还需要引入spring-cloud-loadbalancer的依赖，否则就会报错