一个最简单的使用FeignClient的例子如下：

1，添加maven依赖

org.springframework.cloud

spring-cloud-starter-openfeign

2.0.2.RELEASE

io.github.openfeign

feign-core

9.7.0

io.github.openfeign

feign-slf4j

9.7.0

2，在main主入口类添加FeignClients启用注解

@EnableFeignClients

......

3，编写FeignClient代码

@FeignClient(name = "myFeignClient", url = "http://127.0.0.1:8001")

public interface MyFeignClient {

@RequestMapping(method = RequestMethod.GET, value = "/participate")

String getCategorys(@RequestParam Map params);

}

4，直接使用FeignClient

@Autowired

MyFeignClient myFeignClient;

到此，FeignClient便可正常使用一般的Http接口了~

5，如果想使用文件上传接口或者post的x-www-form-urlencoded接口，那需要做如下配置

添加依赖包

io.github.openfeign.form

feign-form

3.4.1

io.github.openfeign.form

feign-form-spring

3.4.1

commons-fileupload

commons-fileupload

1.3.3

添加bean注解配置

@Bean

@Primary

@Scope("prototype")

public Encoder multipartFormEncoder(ObjectFactory messageConverters) {

return new SpringFormEncoder(new SpringEncoder(messageConverters));

}

定义文件上传接口

@RequestMapping(value = {"/demo/v1/upload"},

method = {RequestMethod.POST},

consumes = {MediaType.MULTIPART_FORM_DATA_VALUE})

ReturnResult uploadFile(

@RequestPart(value = "file") MultipartFile file,

@RequestParam(value = "bucketName", required = false) String bucketName);

6，如果想使用Apache的httpclient的连接池，可以做如下配置

添加依赖

org.apache.httpcomponents

httpclient

4.5.6

io.github.openfeign

feign-httpclient

9.7.0

添加属性配置

feign:

okhttp:

enabled: false

httpclient:

enabled: true

maxConnections: 20480

maxConnectionsPerRoute: 512

timeToLive: 60

connectionTimeout: 10000

userAgent: 'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:37.0) Gecko/20100101 Firefox/37.0'

引入FeignAutoConfiguration配置

@Import(FeignAutoConfiguration.class)

@Configuration

public class FeignConfig {

...

}

经过这几步操作后，便可启用Apache的httpclient替换其内嵌httpclient。

7，如果想启用hystrix熔断降级，则可作如下配置

添加依赖

io.github.openfeign

feign-hystrix

9.7.0

添加属性配置

feign:

hystrix:

enabled: true

hystrix:

command:

default:

execution:

isolation:

thread:

timeoutInMilliseconds: 15000

threadpool:

default:

coreSize: 40

maximumSize: 100

maxQueueSize: 100

添加降级策略

public class MyFeignClientFallback implements MyFeignClient {

@Override

public ReturnResult uploadFile(MultipartFile file, String bucketName) {

return new ReturnResult<>(5001);

}

}

添加bean配置

@Bean

@Scope("prototype")

public Feign.Builder feignBuilder() {

return HystrixFeign.builder();

}

@Bean

public MyFeignClientFallback fb() {

return new MyFeignClientFallback();

}

更新@FeignClient代码

@FeignClient(

name = "myFeignClient",

url = "http://127.0.0.1:8001",

fallback = MyFeignClientFallback.class,

configuration = {FeignConfig.class})

8，如果想处理熔断的具体原因，可以做如下更新

更新熔断策略代码实现FallbackFactory接口

public class MyFeignClientFallback implements FallbackFactory {

@Override

public MyFeignClient create(final Throwable cause) {

return new MyFeignClient() {

@Override

public ReturnResult uploadFile(MultipartFile file, String bucketName) {

// 处理cause

return new ReturnResult<>(5001);

}

};

}

}

更新bean配置

@Bean

public MyFeignClientFallback fbf() {

return new MyFeignClientFallback();

}

更新@FeignClient代码

@FeignClient(

name = "myFeignClient",

url = "http://127.0.0.1:8001",

fallbackFactory = MyFeignClientFallback.class,

configuration = {FeignConfig.class})

-End-