【微服务】- Spring Cloud Feign(声明式服务调

目录：

• 搭建Spring-Cloud-Feign-Client
• Feign 配置压缩
• Feign 日志配置

Spring Cloud Feign整合了Spring Cloud Ribbon 和Spring Cloud Hystrix，而且还提供了一种比Ribbon更简单的服务调用方式 ——— 声明式服务调用。在Spring Cloud Feign中编写服务调用代码非常简单。

搭建Spring-Cloud-Feign-Client

基于Spring Cloud Ribbon(负载均衡)博文的代码，搭建Spring-Cloud-Feign-Client

1.依赖导入：

        <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.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.10</version>
            <scope>provided</scope>
        </dependency>

2. 启动类

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class FeignClientApplication {

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

3. 项目配置: application.yml

server:
  port: 8771
spring:
  application:
    name: spring-cloud-feign-client
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka

4 定义Feign请求接口
这里我们配合前面Eureka的例子，做一次远程调用

@FeignClient(value = "spring-cloud-ribbon-server")
public interface EurekaFeignService {

    @GetMapping("/users/hello")
    String hello();
}

@FeignClient(value = "spring-cloud-ribbon-server")里面配置的value 就是服务的名称
注意：

1. 如果你在项目里面设置了统一的请求路径(server.servlet.context-path),需要将@FeignClient注解调整@FeignClient(value = "fw-register-eureka-client",path = "xxx")
2. Feign 里面定义的接口，有多个@RequestParam，但只能有不超过一个@RequestBody
3. 在定义接口的时候，如果返回的是用户自定义的实体，建议抽取出来，在Controller中实现接口，将抽取出来的接口单独打包，需要调用的项目依赖此包即可，每个项目不用重新定义一遍

5 定义控制层

@RestController
public class EurekaFeignController {

    @Autowired
    private EurekaFeignService eurekaFeignService;

    @GetMapping("/hello")
    public String hello() {
        return eurekaFeignService.hello();
    }
}

6 启动项目测试：

• 启动spring-cloud-eureka-server
• 启动端口号为8773,8774的spring-cloud-ribbon-server
• 启动spring-cloud-feign-client

访问:http://127.0.0.1:8771/hello

image.png

Feign 配置压缩

Spring Cloud feign支持对请求和响应进行gzip压缩,以减少通信过程中的性能损耗，只有超过这个大小的请求才会对其进行压缩:

添加配置信息：application.yml

feign:
  compression:
    request:
      enabled: true
      mime-types: text/xml,application/xml,application/json
      min-request-size: 2048
    response:
      enabled: true

Feign 配置日志

Feign提供了日志打印的功能，Feign的日志级别分为四种：

• NONE: 不记录任何信息。
• BASIC: 仅记录请求方法、URL以及响应状态码和执行时间。
• HEADERS: 除了记录BASIC级别的信息之外，还会记录请求和响应的头信息。
• FULL: 记录所有请求与响应的明细，包括头信息、请求体、元数据等。

日志级别默认为NONE，要改变级别可以在入口类中定义一个日志配置Bean：

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class FeignClientApplication {

    @Bean
    Logger.Level feignLoggerLevel(){
        return Logger.Level.FULL;
    }

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

然后在yml中配置Feign客户端的日志级别为debug，Feign日志记录仅响应debug级别：

logging:
  level:
    top:
      lconcise:
        feign:
          client:
            service: debug

重启项目访问:http://127.0.0.1:8771/hello，可以看到控制台打印日志如下：

2020-02-14 11:51:56.863 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] <--- HTTP/1.1 200 (498ms)
2020-02-14 11:51:56.864 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] connection: keep-alive
2020-02-14 11:51:56.864 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] content-length: 31
2020-02-14 11:51:56.864 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] content-type: text/plain;charset=UTF-8
2020-02-14 11:51:56.864 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] date: Fri, 14 Feb 2020 03:51:56 GMT
2020-02-14 11:51:56.864 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] keep-alive: timeout=60
2020-02-14 11:51:56.864 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] 
2020-02-14 11:51:56.867 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] Hello Spring-Cloud-Feign-Client
2020-02-14 11:51:56.868 DEBUG 16764 --- [nio-8771-exec-1] t.l.f.client.service.EurekaFeignService  : [EurekaFeignService#hello] <--- END HTTP (31-byte body)

源码：https://github.com/lbshold/springboot/tree/master/Spring-Boot-Ribbon-Demo

参考博文：https://mrbird.cc/Spring-Cloud-Feign.html
https://www.kancloud.cn/xuyisu/springcloud_springboot/1451300