Nacos服務呼叫(基於Openfeign)

在<<Nacos服務註冊>>這篇文章裡，我搭建了一個nacos服務中心，並且註冊了一個服務，下面我們來看在上一篇文章的基礎上，怎樣用Openfeign來呼叫這個服務。

0.同上篇，啟動nacos

1.搭建alibaba spring cloud腳手架

存取https://start.aliyun.com/bootstrap.html,GroupID: com.alibaba.cloud,Artifact:nocos-discovery-consumer-sample。,選擇依賴：Nacos Service Discovery,Spring Web,Cloud Bootstrap.

2.在pom檔案中引入spring-cloud-starter-loadbalancer,注意一定要引入loadbalancer,否則用openfeign呼叫會報錯。

完整的pom檔案如下：

<?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>2.6.11</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>nocos-discovery-consumer-sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>nocos-discovery-consumer-sample</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud-alibaba.version>2021.0.4.0</spring-cloud-alibaba.version>
        <spring-cloud.version>2021.0.4</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>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </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>
            <version>3.0.1</version>
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>${spring-cloud-alibaba.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <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>

</project>

3.設定application.properties

spring.application.name=nocos-discovery-consumer-sample
spring.cloud.nacos.discovery.username=nacos
spring.cloud.nacos.discovery.password=nacos
spring.cloud.nacos.discovery.server-addr=localhost:8848
spring.cloud.nacos.discovery.namespace=public
spring.main.allow-circular-references=true
server.port=9091

注意這一行：spring.cloud.nacos.discovery.server-addr=localhost:8848 ，表明這是nacos服務中心的地址。

4.新建一個Openfeign呼叫類：

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.*;
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClient;

@FeignClient("nocos-discovery-provider-sample") 
@LoadBalancerClient("nocos-discovery-provider-sample")
public interface EchoService {
    
    
    @GetMapping("/echo/{message}")
     public String callEcho(@PathVariable String message);
    
}

這裡要注意的是標註@LoadBalancerClient("nocos-discovery-provider-sample")，nocos-discovery-provider-sample就是上一篇中服務提供方註冊到nacos的名稱.

5.新建一個Controller:

@RestController
public class RestTemplateController {


     
     @Autowired
     private EchoService echoService;
     
     @GetMapping("/call/echo/{message}")
     public String callEcho(@PathVariable String message) {
         
         //openFeign test
         return "From openFeign :"+echoService.callEcho(message);
         
        
         
     }
}

6.SpringBoot啟動類：

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 NocosDiscoveryConsumerSampleApplication {

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

}

記得要加標註@EnableFeignClients

7.存取http://localhost:9091/call/echo/hello