spring cloud开发Greenwich版：服务调用feign（七） | chenying99'blog - 君子博学而日参省乎己，则知明而行无过矣

在实际应用中，spring cloud通常feign组件与服务提供者进行通信，feign有着更友好的api调用方式
我们改造微服务’ralab-client’

Add the Maven spring-cloud-config-server denpendency
Add @EnableFeignClients to the application class
Add FeignClient Interface communicate to microservice ‘ralab-nlp’

Add invoke Interface to RestController NlpResource

<?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>2.1.8.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.ralab</groupId>
    <artifactId>ralab-client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>ralab-client</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.SR3</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</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-netflix-hystrix</artifactId>
        </dependency>       

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!--添加依赖，获取配置服务器的相关配置信息-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </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>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

RalabClientApplication文件

package com.ralab.ralabclient;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
@EnableFeignClients
public class RalabClientApplication {

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate()
    {
        return new RestTemplate();
    }

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

}

EurekaFeignService文件

package com.ralab.ralabclient.services;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient(value = "nlp-service")
public interface EurekaFeignService {

    @RequestMapping(value = "nlp/api")
    String nlpService();
}

然后在NlpResource调用上面的feign接口

package com.ralab.ralabclient.resources;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.ralab.ralabclient.services.EurekaFeignService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@RequestMapping("/nlp")
@RefreshScope
public class NlpResource {

    @Autowired
    private RestTemplate restTemplate;
    
    @Autowired
    private EurekaFeignService eurekaFeignService;

    @Value("${example.property}")
    private String exampleProperty;

    @RequestMapping("/config")
    public String home() {
        return "exampleProperty:" + exampleProperty;
    }

    @GetMapping("/service")
    @HystrixCommand(fallbackMethod = "getFallbackIndex")
    public String index()
    {
      //String result = restTemplate.getForObject("http://localhost:8090/nlp/api", String.class);
      String result = restTemplate.getForObject("http://nlp-service/nlp/api", String.class);
      return result;
    }

    @GetMapping("/feign")
    @HystrixCommand(fallbackMethod = "getFallbackIndex")
    public String feignservice()
    {        
        String result = eurekaFeignService.nlpService();
        return result;
    }

    private String getFallbackIndex()
    {
        //String result = restTemplate.getForObject("http://localhost:8090/nlp/api", String.class);

        return "不好意思，没有获取到服务端信息";
    }
}

运行RalabClientApplication，打开http://localhost:8091/nlp/feign