问题背景

项目开发过程中，由于业务需求，需要通过feign实现微服务间文件传输，但其报错 Error converting request body，通过以下方式进行解决：

1.封装feign注解

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@FeignClient(configuration = MyFeignClientConfiguration.class)
public @interface MyFeignClient {
    @AliasFor(annotation = FeignClient.class)
    String name();

    @AliasFor(annotation = FeignClient.class)
    String url();
}

2.引入gradle依赖

    api 'org.springframework.cloud:spring-cloud-starter-openfeign'
    implementation 'io.github.openfeign:feign-httpclient'
    implementation 'io.github.openfeign:feign-jaxb'
    implementation group: 'io.github.openfeign.form', name: 'feign-form', version: '3.8.0'
    implementation group: 'io.github.openfeign.form', name: 'feign-form-spring', version: '3.8.0'
    implementation group: 'commons-fileupload', name: 'commons-fileupload', version: '1.3.3'

3.被调用方对feign进行配置

@Slf4j
public class MyFeignClientConfiguration {
    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }

    @Bean
    @ConditionalOnClass(HttpServletRequest.class)
    public RequestInterceptor oauth2FeignRequestInterceptor() {
        return new TransitiveAuthRequestInterceptor();
    }

    private static final String REDIRECT_TO_PROPERTY = "endpoint.redirect-to";

    /**
     * 调试时, 可以通过设置 {@link #REDIRECT_TO_PROPERTY endpoint.redirect-to} 参数改变 client 的 目标服务器.
     *
     * <p> 例如, 添加下面的参数, 可以将所有微服务模块的请求发往测试环境.
     *
     * <p> in your {@code application.yml} file:
     *
     * <pre>{@code
     * endpoint:
     *   redirect-to: http://{appName}.internal.mytest.tech
     * }</pre>
     */
    @Bean
    @ConditionalOnClass(HttpServletRequest.class)
    @ConditionalOnProperty(REDIRECT_TO_PROPERTY)
    public RequestInterceptor redirectionInterceptor(@Value("${" + REDIRECT_TO_PROPERTY + "}") String redirectTo) {
        log.warn("Property [{}] set to [{}]. So all @MyFeignClient requests will be redirected. "
                + "Please make sure you are for the debugging purpose. ", REDIRECT_TO_PROPERTY, redirectTo);
        return new EndpointRedirectionInterceptor(redirectTo);
    }

    @Bean
    public FeignErrorDecoder errorDecoder(ObjectMapper objectMapper) {
        return new FeignErrorDecoder(objectMapper);
    }


    @Autowired
    private ObjectFactory<HttpMessageConverters> messageConverters;

    @Bean
    //通过此配置解决微服务间调用报错问题
    public Encoder feignFormEncoder() {
        return new SpringFormEncoder(new SpringEncoder(messageConverters));
    }
}

4.被调用方提供sdk

@MyClient(url = "${endpoint.provider:provider:8061}", name = "provider")
public interface ProviderClient {

    @PostMapping(value = "/v1/provider/open/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    MyResponse upload(@RequestPart("myFile") MultipartFile creativeFile,
                                                    @RequestParam("myParam1") String myParam1,
                                                    @RequestParam("myParam2") String myParam2,
                                                    @RequestParam("myParam3") String myParam3,
                                                    @RequestParam("myParam4") String myParam4);
}

5.调用方service使用

@Slf4j
@Service
@RequiredArgsConstructor
public class CallerService {

    private final ProviderClient providerClient;

    public MyResponse upload(HttpServletRequest request) {
        final String myParam1= request.getParameter("myParam1");
        final String myParam2= request.getParameter("myParam2");
        final String myParam3= request.getParameter("myParam3");
        final String myParam4= request.getParameter("myParam4");
        MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
        MultipartFile file = multipartHttpServletRequest.getFile("myFile");
        return providerClient.upload(file,
                myParam1, myParam2, myParam3, myParam4);
    }
}

6.调用方controller层

@Slf4j
@RestController
@RequiredArgsConstructor
@RequestMapping("/v1/call")
public class CallerController {

    private final CallerService callerService ;

    @PostMapping(value = "/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    @ApiOperation("上传")
    @CrossOrigin
    public MyResponse upload(HttpServletRequest request) {
        return callerService .upload(request);
    }
}

7.总结

出现问题第一时间看是什么问题，再根据问题去定位到官方网站去查询，要会正确的搜索是很重要的。