这两天老大突然交给一个任务，就是当用户关注我们的微信号时，我们应该将其微信头像下载下来，然后上传到公司内部的服务器上。如果直接保存微信头像的链接，当用户更换微信头像时，我们的产品在获取用户头像很可能会出现404异常。
由于公司运用的技术栈为spring Cloud（一些Eureka, Feign）进行服务注册和远程调用。
重点来了。。。。但直接使用FeignClient去远程调用注册中心上的上传文件接口，会一直报错。
@PostMapping
@ApiOperation(value = "上传文件")
public String fileUpload(@ApiParam(value = "文件", required = true) @RequestParam("file") MultipartFile multipartFile,
@ApiParam(value = "usage(目录)", required = false) @RequestParam(value = "usage", required = false) String usage,
@ApiParam(value = "同步(可选,默认false)") @RequestParam(value = "sync", required = false, defaultValue = "false") boolean sync) {
if (multipartFile == null) {
throw new IllegalArgumentException("参数异常");
}
String url = map.get(key).doUpload(multipartFile, usage, sync);
return UploadResult.builder().url(url).build();
}
远程的上传文件的接口。
@FeignClient("dx-commons-fileserver")
public interface FileServerService {
@RequestMapping(value="/file", method = RequestMethod.POST)
public String fileUpload(
@RequestParam("file") MultipartFile multipartFile,
@RequestParam(value = "usage", required = false) String usage,
@RequestParam(value = "sync", required = false, defaultValue = "false") boolean sync);
}
普通的FeignClient远程调用代码。但是这样的实现，在去调用的时候一直抛异常：MissingServletRequestPartException，"Required request part 'file' is not present"
这里去跟踪：fileServerService.fileUpload(multipartFile, null, true)源码发现发送的url是将multipartFile以url的方式拼接在query string上。所以这样的调用肯定是不行的。
那从百度搜索了一下关键词: feign upload 会看到有这样一种解决方案：
(原文转自:http://www.jianshu.com/p/dfecfbb4a215)
maven
<dependency>
<groupId>io.github.openfeign.form</groupId>
<artifactId>feign-form</artifactId>
<version>2.1.0</version>
</dependency>
<dependency>
<groupId>io.github.openfeign.form</groupId>
<artifactId>feign-form-spring</artifactId>
<version>2.1.0</version>
</dependency>feign config
@Configuration
public class FeignMultipartSupportConfig {
@Bean
@Primary
@Scope("prototype")
public Encoder multipartFormEncoder() {
return new SpringFormEncoder();
}
@Bean
public feign.Logger.Level multipartLoggerLevel() {
return feign.Logger.Level.FULL;
}
}feign client
@FeignClient(name = "xxx",configuration = FeignMultipartSupportConfig.class)
public interface OpenAccountFeignClient {
@RequestMapping(method = RequestMethod.POST, value = "/xxxxx",produces = {MediaType.APPLICATION_JSON_UTF8_VALUE},consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public ResponseEntity<?> ocrIdCard(@RequestPart(value = "file") MultipartFile file);
}这种方案很好很强大，照搬过来就很好的解决了问题。也实现了文件上传的远程调用。
但是问题又来了。因为上面的成功是很大一部分源于那个配置类，里面的Encoder Bean。但我的这个项目里不止需要远程调用上传的接口，还需要调用其他的接口。这样的话会发现其他FeignClient一调用，就会抛异常。真的是一波未平一波又起。心碎的感觉。跟踪源码发现：
SpringFormEncoder的encode方法当传送的对象不是MultipartFile的时候，就会调用Encoder.Default类的encode方法。。。。。。。。。。。
public class SpringFormEncoder extends FormEncoder {
private final Encoder delegate;
public SpringFormEncoder () {
this(new Encoder.Default());
}
public SpringFormEncoder(Encoder delegate) {
this.delegate = delegate;
}
@Override
public void encode(Object object, Type bodyType, RequestTemplate template) throws EncodeException {
if (!bodyType.equals(MultipartFile.class)) {
delegate.encode(object, bodyType, template);
return;
}
MultipartFile file = (MultipartFile) object;
Map<String, Object> data = Collections.singletonMap(file.getName(), object);
new SpringMultipartEncodedDataProcessor().process(data, template);
}
}
而这个Encoder.Default的encode方法判断传送的类型不是String或者byte[]，就会抛异常：
class Default implements Encoder {
@Override
public void encode(Object object, Type bodyType, RequestTemplate template) {
if (bodyType == String.class) {
template.body(object.toString());
} else if (bodyType == byte[].class) {
template.body((byte[]) object, null);
} else if (object != null) {
throw new EncodeException(
format("%s is not a type supported by this encoder.", object.getClass()));
}
}
}
就这样，我又得继续寻找其他的方法，不然没法远程调用其他的服务了。这就很尴尬。
那接下来就是各种FQ，各种谷歌，终于找到了合适的答案。
原文转自（https://github.com/pcan/feign-client-test 可将示例代码下载下来研究，这样方便看调用的逻辑）
Feign Client Test
A Test project that uses Feign to upload Multipart files to a REST endpoint. Since Feign library does not support Multipart requests, I wrote a custom Encoder that enables this feature, using a HttpMessageConverter chain that mimics Spring's RestTemplate.
Multipart Request Types
A few request types are supported at the moment:
- Simple upload requests: One
MultipartFilealongwith some path/query parameters:
interface TestUpload {
@RequestLine("POST /upload/{folder}")
public UploadInfo upload(@Param("folder") String folder, @Param("file") MultipartFile file);
}
- Upload one file & object(s): One
MultipartFilealongwith some path/query parameters and one or more JSON-encoded object(s):
interface TestUpload {
@RequestLine("POST /upload/{folder}")
public UploadInfo upload(@Param("folder") String folder, @Param("file") MultipartFile file, @Param("metadata") UploadMetadata metadata);
}
- Upload multiple files & objects: An array of
MultipartFilealongwith some path/query parameters and one or more JSON-encoded object(s):
interface TestUpload {
@RequestLine("POST /uploadArray/{folder}")
public List<UploadInfo> uploadArray(@Param("folder") String folder, @Param("files") MultipartFile[] files, @Param("metadata") UploadMetadata metadata);
}
根据上面的示例代码的提示，我也就按照上面的修改我的代码。因为原理方面没有深入的研究，所以很多代码直接复制过来修改一下。其中有一段：
Feign.Builder encoder = Feign.builder()
.decoder(new JacksonDecoder())
.encoder(new FeignSpringFormEncoder());
这里的encoder是示例代码自己定义的（本人的代码也用到了这个类），decoder用的是JacksonDecoder，那这块我也直接复制了。然后修改好代码为：
@Service
public class UploadService {
@Value("${commons.file.upload-url}")
private String HTTP_FILE_UPLOAD_URL;//此处配置上传文件接口的域名(http(s)://XXXXX.XXXXX.XX)
public String uploadFile(MultipartFile file, String usage, boolean sync){
FileUploadResource fileUploadResource = Feign.builder()
.decoder(new JacksonDecoder())
.encoder(new FeignSpringFormEncoder())
.target(FileUploadResource.class, HTTP_FILE_UPLOAD_URL);
return fileUploadResource.fileUpload(file, usage, sync);
}
}
public interface FileUploadResource {
@RequestLine("POST /file")
String fileUpload(@Param("file") MultipartFile file, @Param("usage") String usage, @Param("sync") boolean sync);
}
其中调用上传文件的代码就改为上述的代码进行运行。但是这样还是抛了异常。跟踪fileUploadResource.fileUpload(file, usage, sync)代码，一步步发现远程的调用和文件的上传都是OK的，响应也是为200.但是最后的decoder时，抛异常：
unrecognized token 'http': was expecting ('true', 'false' or 'null')
只想说 What a fucking day!!! 这里也能出错？？心里很是郁闷。。。。没办法，这个方法还是很厉害的，因为不会影响其他远程服务的调用，虽然只是这里报错。那只有再次跟踪源码，发现在JacksonDecoder的decode方法：
@Override
public Object decode(Response response, Type type) throws IOException {
if (response.status() == 404) return Util.emptyValueOf(type);
if (response.body() == null) return null;
Reader reader = response.body().asReader();
if (!reader.markSupported()) {
reader = new BufferedReader(reader, 1);
}
try {
// Read the first byte to see if we have any data
reader.mark(1);
if (reader.read() == -1) {
return null; // Eagerly returning null avoids "No content to map due to end-of-input"
}
reader.reset();
return mapper.readValue(reader, mapper.constructType(type));
} catch (RuntimeJsonMappingException e) {
if (e.getCause() != null && e.getCause() instanceof IOException) {
throw IOException.class.cast(e.getCause());
}
throw e;
}
}
其中走到： return mapper.readValue(reader, mapper.constructType(type)); 然后就抛异常啦。郁闷啊。最后不知道一下子咋想的，就尝试把这个decoder删除，不设置decoder了。那终于万幸啊。。。。全部调通了。。。。。。。所以修改完的UploadService代码为：
@Service
public class UploadService {
@Value("${commons.file.upload-url}")
private String HTTP_FILE_UPLOAD_URL;//此处配置上传文件接口的域名(http(s)://XXXXX.XXXXX.XX)
public String uploadFile(MultipartFile file, String usage, boolean sync){
FileUploadResource fileUploadResource = Feign.builder()
.encoder(new FeignSpringFormEncoder()) //这里没有添加decoder了
.target(FileUploadResource.class, HTTP_FILE_UPLOAD_URL);
return fileUploadResource.fileUpload(file, usage, sync);
}
}
写这篇博客是因为这个问题花费了我一天多的时间，所以我一定得记下来，不然下次遇到了，可能还是会花费一些时间才能搞定。不过上面提到的示例代码还真的是牛。后面还得继续研究一下。
希望这些记录能对那些和我一样遇到这样问题的小伙伴有所帮助，尽快解决问题。