SpringCloud組件之Feign(Hoxton版本)

1.Feign簡介

Feign是一個聲明式的僞Http客戶端，它使得寫Http客戶端變得更簡單。使用Feign，只需要創建一個接口並註解。它具有可插拔的註解特性，可使用Feign 註解和JAX-RS註解。Feign支持可插拔的編碼器和解碼器。Feign默認集成了Ribbon，並和Eureka結合，默認實現了負載均衡的效果。 簡而言之：

• Feign 採用的是基於接口的註解;
• Feign 整合了ribbon，具有負載均衡的能力;
• 整合了Hystrix，具有熔斷的能力.

2.創建Feign調用演示工程

2.1 準備工作

啓動上篇中Eureka演示工程中Eureka Server與Eureka Client Provider服務 並在Eureka Client Provider中Controller增加一個接口用於Feign調用測試

@RestController
@RequestMapping("/demo")
public class DemoController {

    @Value("${server.port:#{null}}")
    private String serverPort;

    @GetMapping("/hello")
    public String hello() {
        return "Hello " + serverPort;
    }

    @GetMapping("/feign")
    public String feignTest(@RequestParam(value = "name") String name){
        return "Hello Feign "+ name;
    }

}

2.2 創建一個服務消費者

新建一個maven工程，取名爲：spring-cloud-feign-demo,添加如下依賴pom.xml中

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>spring-cloud-demo</artifactId>
        <groupId>com.hxmec</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>spring-cloud-feign-demo</artifactId>

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

新建application.yml，增加下面的配置

server:
  port: 9003
spring:
  application:
    name: feign-demo
logging:
  pattern:
    console: '%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%thread] %logger{15} - %msg%n'
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8888/eureka/

創建一個啓動類 FeignDemoApplication，添加Feign相關注解

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
@EnableFeignClients
public class FeignDemoApplication {

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

編寫Feign接口服務

@FeignClient(value = "eureka-client-provider")//此名稱爲消費提供者註冊的服務名稱
public interface FeignService {

    @RequestMapping(value = "/demo/feign",method = RequestMethod.GET)
    String feignTest(@RequestParam(value = "name") String name);
}

編寫Controller層調用Feign接口實例

@RestController
@RequestMapping("/feign")
@AllArgsConstructor
public class FeignClientController {

    private final FeignService feignService;

    @GetMapping(value = "/test1")
    public String feign(@RequestParam String name) {
        return feignService.feignTest(name);
    }

}

啓動項目，打開http://localhost:8888/ 可以看到應用已經註冊到Eureka註冊中心

請求http://localhost:9003/feign/test1?name=Trazen 驗證是否成功調用服務提供者接口

3.項目git地址

https://github.com/ty1972873004/spring-cloud-demo

4.參考

【官方文檔】https://cloud.spring.io/spring-cloud-netflix/multi/multi_spring-cloud-ribbon.html