Fegin简介

Fegin是声明式、模块化的Http客户端，可以帮助我们快捷优雅的调用HTTP接口。
在SpringCloud中可以很方便的创建一个Feign客户端，只需声明一个接口，并加上对应的注解就能完成对HTTP接口的调用。

本文不集成注册中心也就不使用Fegin的负载均衡，所以可以理解为一个更简便，高可复用的Http客户端。

以示例讲解

SpringBoot版本：2.1.1.RELEASE
SpringCloud版本：Finchley.SR2

必要POM引入

<parent>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>2.1.1.RELEASE</version>    </parent>    <dependencyManagement>        <dependencies>            <!--spring-cloud -->            <dependency>                <groupId>org.springframework.cloud</groupId>                <artifactId>spring-cloud-dependencies</artifactId>                <version>${spring-cloud.version}</version>                <type>pom</type>                <scope>import</scope>            </dependency>        </dependencies>    </dependencyManagement>    <dependencies>        <dependencies>            <dependency>                <groupId>org.springframework.boot</groupId>                <artifactId>spring-boot-starter-web</artifactId>        </dependency>    </dependencies>

Fegin客户端定义

1、@FeignClient 定义接口为Http客户端,调用指定方法,并将接口注入Spring上下文中参数url：所请求http服务的url、参数config：指定fegin的配置类2、@PostMapping 为@RequestMapping的组合注解,默认为Post请求调用，注解不多介绍，主要表示所需要调用的http接口的具体路径,可在url中拼接参数，也可以指定入参的ContentType3、http接口的返回值格式如果和返回对象属性一致,会反序列化为对应对象。
package com.external.feign;import java.util.List;import java.util.Map;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.web.bind.annotation.PostMapping;import com.external.config.FormFeignConfig;import com.external.dto.response.BaseBispDto;import com.external.dto.response.NiftyRes;import com.external.dto.response.ReportAnalyzesRes;import com.external.dto.response.ReportSummaryRes;import com.external.feign.rpc.BISPResponse;@FeignClient(name="fegin-name", url="${http-url}" , configuration = FormFeignConfig.class)public interface BispClient {        /**     * @Description      * @author zengzp     */    @PostMapping(value="/intf?method=XXXX", consumes = {"application/x-www-form-urlencoded"})    public XXXXResponse<BaseBispDto> saveSampleInfo(Map<String, ?> params);    /**     * @Description      * @author zengzp     */    @PostMapping(value="/intf?method=XXXX", consumes = {"application/x-www-form-urlencoded"})    public XXXXResponse<NiftyRes> getNiftyDetectionResultReplenish(Map<String, ?> params);

Fegin配置代码

配置日志输出策略与指定对应ContentType的消息的编码与解码
package com.external.config;import org.springframework.beans.factory.ObjectFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.autoconfigure.http.HttpMessageConverters;import org.springframework.cloud.openfeign.support.SpringDecoder;import org.springframework.cloud.openfeign.support.SpringEncoder;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.Scope;import feign.Logger;import feign.codec.Decoder;import feign.codec.Encoder;import feign.form.FormEncoder;@Configurationpublic class FormFeignConfig {    @Autowired    private ObjectFactory<HttpMessageConverters> messageConverters;    @Bean    Logger.Level feignLoggerLevel() {        return Logger.Level.BASIC;    }        @Bean    @Scope("prototype")    Decoder decoder() {        return new AllinpayDecoder(new SpringDecoder(messageConverters));    }        @Bean    @Scope("prototype")    Encoder encoder(){        return new FormEncoder(new SpringEncoder(this.messageConverters));    }}

统一响应DTO

package com.external.feign.rpc;import org.springframework.http.HttpStatus;import com.external.common.dto.BaseDto;public class XXXXResponse<T> extends BaseDto {    /**     *      */    private static final long serialVersionUID = 1L;    private String code;    private String msg;    private Long total;    private T rows;}
启动服务时务必在配置类上增加@EnableFeignClients