SpringCloud使用Fegin進行HTTP接口調用

Fegin簡介

Fegin是聲明式、模塊化的Http客戶端，能夠幫助咱們快捷優雅的調用HTTP接口。
在SpringCloud中能夠很方便的建立一個Feign客戶端，只需聲明一個接口，並加上對應的註解就能完成對HTTP接口的調用。

本文不集成註冊中心也就不使用Fegin的負載均衡，因此能夠理解爲一個更簡便，高可複用的Http客戶端。

以示例講解

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客戶端定義

一、@FeignClient 定義接口爲Http客戶端,調用指定方法,並將接口注入Spring上下文中
參數url：所請求http服務的url、參數config：指定fegin的配置類
二、@PostMapping 爲@RequestMapping的組合註解,默認爲Post請求調用，註解很少介紹，
主要表示所須要調用的http接口的具體路徑,可在url中拼接參數，也能夠指定入參的ContentType
三、http接口的返回值格式若是和返回對象屬性一致,會反序列化爲對應對象。

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配置代碼

配置日誌輸出策略與指定對應ContentType的消息的編碼與解碼

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;

@Configuration
public 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));
    }
}

統一響應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;
}

啓動服務時務必在配置類上增長@EnableFeignClients