使用Feign访问服务

内容纲要

认识 Feign

Feign

声明式RESTWeb 服务客户端
https://github.com/OpenFeign/feign

Spring Cloud OpenFeign

pom.xml 中引入依赖

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

Feign的简单使用

开启Feign支持

@EnableFeignClients

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

定义 Feign 接口

@FeignClient

StoreClient.java

@FeignClient("stores")
public interface StoreClient {
    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    List<Store> getStores();

    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    Page<Store> getStores(Pageable pageable);

    @RequestMapping(method = RequestMethod.POST, value = "/stores/{storeId}", consumes = "application/json")
    Store update(@PathVariable("storeId") Long storeId, Store store);

    @RequestMapping(method = RequestMethod.DELETE, value = "/stores/{storeId:\\d+}")
    void delete(@PathVariable Long storeId);
}

简单配置

FeignClientsConfiguration
Encoder / Decoder / Logger / Contract / Client ...

通过配置定制Feign

application.yml

spring:
    cloud:
        openfeign:
            client:
                config:
                    feignName:
                        url: http://remote-service.com
                        connectTimeout: 5000
                        readTimeout: 5000
                        loggerLevel: full
                        errorDecoder: com.example.SimpleErrorDecoder
                        retryer: com.example.SimpleRetryer
                        defaultQueryParameters:
                            query: queryValue
                        defaultRequestHeaders:
                            header: headerValue
                        requestInterceptors:
                            - com.example.FooRequestInterceptor
                            - com.example.BarRequestInterceptor
                        responseInterceptor: com.example.BazResponseInterceptor
                        dismiss404: false
                        encoder: com.example.SimpleEncoder
                        decoder: com.example.SimpleDecoder
                        contract: com.example.SimpleContract
                        capabilities:
                            - com.example.FooCapability
                            - com.example.BarCapability
                        queryMapEncoder: com.example.SimpleQueryMapEncoder
                        micrometer.enabled: false

Feign的其他配置

配置okhttp

feign.okhttp.enabled=true
配置httpclient（注意需要引入相关包）
feign.httpclient.enabled=true

配置压缩

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

server.port=0
服务器将会自动选择一个空闲的端口来运行

注意：不要在Feign接口上加@Requestmapping，避免出现一些问题(SpringMVC 会视图加载接口上定义的@RequestMapping)。
公共前缀，可以这样做：

@FeignClient(name = "xxx-service", contextId = "coffee", path="/commonPrefixHere")

如果有2个接口都注明了@FeignClient(name = "xxx-service"），contextId可以区分开，避免冲突。