工作上，遇到一个问题。我需要用@FeignClient远程调用文件服务，下载一个doc文件,把它转换成ceb或pdf文件，在上传到文件系统。其实我就是在开发文件转换服务。那么，我们该怎么用FeignClient来下载文件？

Spring将响应转换为字节数组ByteArrayHttpMessageConverter，但它支持application / octet-stream和/ media类型。我们可以用byte[]来接收文件。例如下面这样写：

@FeignClient(value = "epolicy", path = "/epolicy/download", url = "http://10.1.118.45:8001") public interface EPolicyApi {@RequestMapping(method = RequestMethod.POST)
byte[] download(@RequestParam("policyNo") String policyNo, @RequestParam("idNo") String idNo);}

但是我们可以学习老外这么写：https://github.com/spring-cloud/spring-cloud-netflix/issues/2246

用feign-form上传文件

<dependency><groupId>io.github.openfeign.form</groupId><artifactId>feign-form</artifactId><version>2.2.1</version>
</dependency><dependency><groupId>io.github.openfeign.form</groupId><artifactId>feign-form-spring</artifactId><version>2.2.1</version>
</dependency

import org.springframework.util.FileCopyUtils;
import org.springframework.web.multipart.MultipartFile;import java.io.*;public class InMemoryMultipartFile implements MultipartFile {private final String name;private final String originalFileName;private final String contentType;private final byte[] payload;public InMemoryMultipartFile(File file) throws IOException {this.originalFileName = file.getName();this.payload = FileCopyUtils.copyToByteArray(file);this.name = "file";this.contentType = "application/octet-stream";}public InMemoryMultipartFile(String originalFileName, byte[] payload) {this.originalFileName = originalFileName;this.payload = payload;this.name = "file";this.contentType = "application/octet-stream";}public InMemoryMultipartFile(String name, String originalFileName, String contentType, byte[] payload) {if (payload == null) {throw new IllegalArgumentException("Payload cannot be null.");}this.name = name;this.originalFileName = originalFileName;this.contentType = contentType;this.payload = payload;}@Overridepublic String getName() {return name;}@Overridepublic String getOriginalFilename() {return originalFileName;}@Overridepublic String getContentType() {return contentType;}@Overridepublic boolean isEmpty() {return payload.length == 0;}@Overridepublic long getSize() {return payload.length;}@Overridepublic byte[] getBytes() throws IOException {return payload;}@Overridepublic InputStream getInputStream() throws IOException {return new ByteArrayInputStream(payload);}@Overridepublic void transferTo(File dest) throws IOException, IllegalStateException {new FileOutputStream(dest).write(payload);}
}

@FeignClient(value = "material", configuration = MaterialClient.MultipartSupportConfig.class)
public interface MaterialClient {@PostMapping("/uploadFile")@Headers("Content-Type: multipart/form-data")ResponseMO uploadFile(@RequestPart("file") MultipartFile file);@GetMapping("/oss/downFile")MultipartFile downFile(@RequestParam("key") String key);class MultipartSupportConfig {@AutowiredObjectFactory<HttpMessageConverters> messageConverters;@Bean@Primary@Scope("prototype")public Encoder multipartFormEncoder() {return new SpringFormEncoder(new SpringEncoder(messageConverters));}@Bean@Primary@Scope("prototype")public Decoder decoder() {Decoder decoder = (response, type) -> {if (type instanceof Class && MultipartFile.class.isAssignableFrom((Class) type)) {Collection<String> contentTypes = response.headers().get("content-type");String contentType = "application/octet-stream";if (contentTypes.size() > 0) {String[] temp = new String[contentTypes.size()];contentTypes.toArray(temp);contentType = temp[0];}byte[] bytes = StreamUtils.copyToByteArray(response.body().asInputStream());InMemoryMultipartFile inMemoryMultipartFile = new InMemoryMultipartFile("file","", contentType,bytes);return inMemoryMultipartFile;}return new SpringDecoder(messageConverters).decode(response, type);};return new ResponseEntityDecoder(decoder);}}
}