使用Feign扩展包实现微服务间文件上传

在Spring Cloud 的Feign组件中并不支持文件的传输，会出现这样的错误提示：

feign.codec.EncodeException: class [Lorg.springframework.web.multipart.MultipartFile; is not a type supported by this encoder.
  at feign.codec.Encoder$Default.encode(Encoder.java:90) ~[feign-core-9.5.1.jar:na]
  at feign.form.FormEncoder.encode(FormEncoder.java:87) ~[feign-form-3.3.0.jar:3.3.0]
  at feign.form.spring.SpringFormEncoder.encode(SpringFormEncoder.java:64) ~[feign-form-spring-3.3.0.jar:3.3.0]

但是我们可以通过使用Feign的扩展包实现这个功能。

一. 示例介绍

我们调用feign_upload_second的上传文件接口上传文件，feign_upload_second内部使用feign调用feign_upload_first实现文件上传。

二 、单文件上传

2.1 feign_upload_first服务提供者

文件上传的服务提供者接口比较简单，如下所示：

@SpringBootApplication
public class FeignUploadFirstApplication {
 @RestController
 public class UploadController {

  @RequestMapping(value = "/uploadFile",method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
  public String handleFileUpload(@RequestPart(value = "file") MultipartFile file) {
   return file.getOriginalFilename();
  }
 }
 public static void main(String[] args) {
  SpringApplication.run(FeignUploadFirstApplication.class, args);
 }
}

2.2 feign_upload_second服务消费者

增加扩展包依赖

<dependency>
   <groupId>io.github.openfeign.form</groupId>
   <artifactId>feign-form</artifactId>
   <version>3.3.0</version>
  </dependency>
  <dependency>
   <groupId>io.github.openfeign.form</groupId>
   <artifactId>feign-form-spring</artifactId>
   <version>3.3.0</version>
  </dependency>
  <dependency>
   <groupId>commons-fileupload</groupId>
   <artifactId>commons-fileupload</artifactId>
   <version>1.3.3</version>
</dependency>

新增feign实现文件上传的配置类

@Configuration
public class FeignSupportConfig {
 @Bean
 public Encoder feignFormEncoder() {
  return new SpringFormEncoder();
 }
}

feign远程调用接口

@FeignClient(name = "file",url = "http://localhost:8100",configuration = FeignSupportConfig.class)
public interface UploadService {
 @RequestMapping(value = "/uploadFile", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 String handleFileUpload(@RequestPart(value = "file") MultipartFile file);
}

上传文件接口

@RestController
public class UploadController {
 @Autowired
 UploadService uploadService;

 @RequestMapping(value = "/uploadFile",method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 public String handleFileUpload(@RequestPart(value = "file") MultipartFile file) {
  return uploadService.handleFileUpload(file);
 }
}

2.3 测试

使用postman进行测试，可以正常上传文件

三、多文件上传

既然单个文件可以上传，那么多文件应该也没问题吧，我们对上面的代码进行修改

3.1 feign_upload_first服务提供者

文件上传的服务提供者接口比较简单，如下所示：

@SpringBootApplication
public class FeignUploadFirstApplication {
 @RestController
 public class UploadController {

  @RequestMapping(value = "/uploadFile",method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
  public String handleFileUpload(@RequestPart(value = "file") MultipartFile file) {
   return file.getOriginalFilename();
  }

  @RequestMapping(value = "/uploadFile2",method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
  public String handleFileUpload(@RequestPart(value = "file") MultipartFile[] file) {
   String fileName = "";
   for(MultipartFile f : file){
    fileName += f.getOriginalFilename()+"---";
   }
   return fileName;
  }
 }
 public static void main(String[] args) {
  SpringApplication.run(FeignUploadFirstApplication.class, args);
 }
}

3.2 feign_upload_second服务消费者

feign远程调用接口

@FeignClient(name = "file",url = "http://localhost:8100",configuration = FeignSupportConfig.class)
public interface UploadService {
 @RequestMapping(value = "/uploadFile", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 String handleFileUpload(@RequestPart(value = "file") MultipartFile file);

 @RequestMapping(value = "/uploadFile2", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 String handleFileUpload(@RequestPart(value = "file") MultipartFile[] file);
}

上传文件接口

@RestController
public class UploadController {
 @Autowired
 UploadService uploadService;

 @RequestMapping(value = "/uploadFile",method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 public String handleFileUpload(@RequestPart(value = "file") MultipartFile file) {
  return uploadService.handleFileUpload(file);
 }

 @RequestMapping(value = "/uploadFile2",method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 public String handleFileUpload2(@RequestPart(value = "file") MultipartFile[] file) {
  return uploadService.handleFileUpload(file);
 }
}

3.3 测试

经过测试发现，无法上传多个文件。经过检查，发现源码里底层是有对MultipartFile[]类型的支持的，源码中有个类叫SpringManyMultipartFilesWriter，是专门针对文件数组类型进行操作的，但是配置到项目里的SpringFormEncoder类里却没有对文件数组类型的判断，以致不能支持文件数组的上传

SpringManyMultipartFilesWriter源码

public class SpringManyMultipartFilesWriter extends AbstractWriter {
 private final SpringSingleMultipartFileWriter fileWriter = new SpringSingleMultipartFileWriter();

 public SpringManyMultipartFilesWriter() {
 }

 public void write(Output output, String boundary, String key, Object value) throws Exception {
  if (value instanceof MultipartFile[]) {
   MultipartFile[] files = (MultipartFile[])((MultipartFile[])value);
   MultipartFile[] var6 = files;
   int var7 = files.length;

   for(int var8 = 0; var8 < var7; ++var8) {
    MultipartFile file = var6[var8];
    this.fileWriter.write(output, boundary, key, file);
   }
  } else if (value instanceof Iterable) {
   Iterable<?> iterable = (Iterable)value;
   Iterator var11 = iterable.iterator();

   while(var11.hasNext()) {
    Object file = var11.next();
    this.fileWriter.write(output, boundary, key, file);
   }
  }

 }

 public boolean isApplicable(Object value) {
  if (value == null) {
   return false;
  } else if (value instanceof MultipartFile[]) {
   return true;
  } else {
   if (value instanceof Iterable) {
    Iterable<?> iterable = (Iterable)value;
    Iterator<?> iterator = iterable.iterator();
    if (iterator.hasNext() && iterator.next() instanceof MultipartFile) {
     return true;
    }
   }

   return false;
  }
 }
}

SpringFormEncoder源码

public class SpringFormEncoder extends FormEncoder {
 public SpringFormEncoder() {
  this(new Default());
 }

 public SpringFormEncoder(Encoder delegate) {
  super(delegate);
  MultipartFormContentProcessor processor = (MultipartFormContentProcessor)this.getContentProcessor(ContentType.MULTIPART);
  processor.addWriter(new SpringSingleMultipartFileWriter());
  processor.addWriter(new SpringManyMultipartFilesWriter());
 }

 public void encode(Object object, Type bodyType, RequestTemplate template) throws EncodeException {
  if (!bodyType.equals(MultipartFile.class)) {
   super.encode(object, bodyType, template);
  } else {
   MultipartFile file = (MultipartFile)object;
   Map<String, Object> data = Collections.singletonMap(file.getName(), object);
   super.encode(data, MAP_STRING_WILDCARD, template);
  }
 }
}

从上面SpringFormEncoder的源码上可以看到SpringFormEncoder类构造时把SpringManyMultipartFilesWriter实例添加到了处理器列表里了，但是在encode方法里又只判断了MultipartFile类型，没有判断数组类型，底层有对数组的支持但上层却缺少了相应判断。那么我们可以自己去扩展FormEncoder，仿照SpringFormEncoder源码，只修改encode方法。

3.3 扩展FormEncoder支持多文件上传

扩展FormEncoder,命名为FeignSpringFormEncoder

public class FeignSpringFormEncoder extends FormEncoder {
 /**
  * Constructor with the default Feign's encoder as a delegate.
  */
 public FeignSpringFormEncoder() {
  this(new Default());
 }

 /**
  * Constructor with specified delegate encoder.
  *
  * @param delegate delegate encoder, if this encoder couldn't encode object.
  */
 public FeignSpringFormEncoder(Encoder delegate) {
  super(delegate);

  MultipartFormContentProcessor processor = (MultipartFormContentProcessor) getContentProcessor(ContentType.MULTIPART);
  processor.addWriter(new SpringSingleMultipartFileWriter());
  processor.addWriter(new SpringManyMultipartFilesWriter());
 }

 @Override
 public void encode(Object object, Type bodyType, RequestTemplate template) throws EncodeException {
  if (bodyType.equals(MultipartFile.class)) {
   MultipartFile file = (MultipartFile) object;
   Map data = Collections.singletonMap(file.getName(), object);
   super.encode(data, MAP_STRING_WILDCARD, template);
   return;
  } else if (bodyType.equals(MultipartFile[].class)) {
   MultipartFile[] file = (MultipartFile[]) object;
   if(file != null) {
    Map data = Collections.singletonMap(file.length == 0 ? "" : file[0].getName(), object);
    super.encode(data, MAP_STRING_WILDCARD, template);
    return;
   }
  }
  super.encode(object, bodyType, template);
 }
}

注册配置类

@Configuration
public class FeignSupportConfig {
 @Bean
 public Encoder feignFormEncoder() {
  return new FeignSpringFormEncoder();
 }
}

经过测试可以上传多个文件。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。