SpringCloud之Feign的组件使用

Feign是一个声明式的Web Service客户端，它的目的就是让Web Service调用更加简单。Feign提供了HTTP请求的模板，通过编写简单的接口和插入注解，就可以定义好HTTP请求的参数、格式、地址等信息，感觉是在客户端写服务端的代码，SpringCloud给Feign添加了支持Spring MVC注解，并整合Ribbon及Eureka进行支持负载均衡。

创建服务提供方zx-feign-service

引入主要依赖

    <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-actuator</artifactId>
    </dependency>

主要引入注册中心eureka client的依赖

bootstrap.yml配置信息

spring:
  application:
    name: zx-feign-service

application.yml配置信息

server:
  port: 8004

logging:
  config: classpath:logback.xml

eureka:
  client:
    healthcheck:
      enabled: true
    service-url:
      defaultZone: http://zxdemo:zxdemopwd@127.0.0.1:8002/eureka/
  instance:
    prefer-ip-address: true
    ip-address: 127.0.0.1

编写一个controller

@RestController
@RequestMapping("/api/demo")
public class DemoApiController {

    private static final Logger logger = LoggerFactory.getLogger(DemoApiController.class);

    @Value("${server.port}")
    private String port;

    @Value("${spring.application.name}")
    private String applicationName;

    @GetMapping("getData")
    public String getData(String id) {
        logger.info("/api/demo/getData id:{}",id);

        return applicationName+":"+port+",接收到参数id:"+id;
    }
}

启动类

@SpringBootApplication
@ComponentScan(basePackages = {"com.zx.springcloud.**"})
public class FeignServiceApplication {

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

启动注册中心和服务提供方

启动注册中心(不清楚注册中心eureka搭建的请点击这里),注册中心启动好之后，然后启动feign的服务提供方zx-feign-service，都启动好之后，如图：

可以看到zx-feign-service服务已经注册到eureka上了。

创建服务消费方zx-feign-client

引入依赖

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</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-netflix-hystrix</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
</dependencies>

feign本身是集成了hystrix，所以这里引入hystrix的依赖，以便后续可开启熔断处理。

bootstrap.yml配置

spring:
  application:
    name: zx-feign-client

application.yml配置

server:
  port: 8005

logging:
  config: classpath:logback.xml

eureka:
  client:
    healthcheck:
      enabled: true
    service-url:
      defaultZone: http://zxdemo:zxdemopwd@127.0.0.1:8002/eureka/
  instance:
    prefer-ip-address: true
    ip-address: 127.0.0.1

#开启Hystrix保护
feign:
  hystrix:
    enabled: true

FeignClient的示例

import com.zx.springcloud.feignclient.demo.feign.impl.DemoFeignClientHystric;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(value = "zx-feign-service",fallback = DemoFeignClientHystric.class)
public interface DemoFeignClient {
	
    @GetMapping("/api/demo/getData")
    String getData(@RequestParam("id") String id);
}

使用@FeignClient来实现feign的调用

FeignClient的fallback(熔断处理)的示例代码

import com.zx.springcloud.feignclient.demo.feign.DemoFeignClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

@Component
public class DemoFeignClientHystric implements DemoFeignClient {

    private static final Logger logger = LoggerFactory.getLogger(DemoFeignClientHystric.class);
    
    @Override
    public String getData(String id) {
        logger.info("DemoFeignClientHystric->getData熔断了");
        return "";
    }
}

调用示例的controller

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

    private static final Logger logger = LoggerFactory.getLogger(DemoController.class);

    @Autowired
    private DemoFeignClient demoFeignClient;
	
    @GetMapping("getData")
    public String getData(String id) {
        logger.info("/demo/getData id:{}",id);
        String result = demoFeignClient.getData(id);
        logger.info("调用feign服务方的结果:{}",result);

        return "调用feign服务方的数据是："+result;
    }
}

直接注入FeignClient接口即可使用

启动类

@SpringCloudApplication
@EnableHystrix
@ComponentScan(basePackages = {"com.zx.springcloud.**"})
@EnableFeignClients(basePackages = {"com.zx.springcloud.feignclient.**"})
public class FeignClientApplication {

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

启动zx-feign-client，如果没有异常，是会注册到eureka上的，如图：

访问消费方接口：http://127.0.0.1:8005/demo/getData?id=5 结果如图：

日志：

演示一下熔断

把服务提供方zx-feign-service停掉
然后再访问：http://127.0.0.1:8005/demo/getData?id=5，如图：

本文项目源码地址：

https://github.com/cdzxkj/zx_springcloud_demo

转载请注明来自：

https://blog.youkuaiyun.com/javanian

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