微服务之间如何通过feign调用接口上传文件

具体需求：

我们的项目是基于springboot框架的springcloud微服务搭建的，后端服务技术层面整体上分为business服务和core服务，business服务用于作为应用层，直接连接客户端，通常用于聚合数据，core服务用来客户端具体操作不同需求来控制数据库，文件上传是通过客户端上传接口，通过business服务，由服务端调用feign接口，也是第一次做这种文件中转，遇到各种问题，下面是我自己的解决方案，不喜勿喷，代码小白一枚;

一、core服务层接口@requestmapping

属性加上consumes=MediaType.MULTIPART_FORM_DATA_VALUE如下代码

@PostMapping(value = "/upload",consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    @ResponseBody
    public Result<TbFile> upload(@RequestPart(value = "file",required = true) MultipartFile file,
                         @RequestParam(name = "id",required = true) Integer id,
                         @RequestParam(name = "desc",required = false)  String desc,
                         @RequestParam(name = "fileId",required = false) Integer fileId )

解释：@RequestMapping存在以下两个属性：

1.String[] consumes() default {};

2.String[] produces() default {};

两个属性的解释及参考例子：

① 属性produces：指定返回值类型，并且可以设置返回值类型和返回值的字符编码；代码例子参考如下：

属性produces="application/json"时，返回json数据

属性produces="MediaType.APPLICATION_JSON_VALUE;charset=utf-8"时，设置返回数据的字符编码为utf-8

@Controller
@RequestMapping(value = "/getperson", method = RequestMethod.GET, produces="application/json")
public Object getPerson(int id) {
    //实现自己的逻辑调用
  Person p= new person();

    return p;
} 

特别说明：produces="application/json"和注解@ResponseBody是一样的效果，使用了注解其实可以不使用该属性了

② 属性consumes： 指定处理请求当中的提交内容类型（Content-Type）：application/json, text/html等;

代码例子参考如下：

 @PostMapping(value = "/upload",consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    @ResponseBody
    public Result<TbFile> upload(@RequestPart(value = "file",required = true) MultipartFile file,
                         @RequestParam(name = "id",required = true) Integer id,
                         @RequestParam(name = "desc",required = false)  String desc,
                         @RequestParam(name = "fileId",required = false) Integer fileId ){
}

解释： MediaType.MULTIPART_FORM_DATA_VALUE 代表的值为multipart/form-data它会将表单的数据处理为一条消息，以标签为单元，用分隔符分开。既可以上传键值对，也可以上传文件。当上传的字段是文件时，会有Content-Type来表名文件类型；content-disposition，用来说明字段的一些信息；

二、business客户层接口@requestmapping

属性加上consumes=MediaType.MULTIPART_FORM_DATA_VALUE如下代码

   @PostMapping(value = "/upload",produces = MediaType.APPLICATION_JSON_UTF8_VALUE,
            consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    @ResponseBody
    Result<TbFile> upload(@RequestPart(value = "file",required = true) MultipartFile file,
                  @RequestParam(name = "id",required = true) Integer id,
                  @RequestParam(name = "desc",required = false)  String desc,
                  @RequestParam(name = "fileId",required = false) Integer fileId );

具体大概就这么多。能力有限，多多指教!!!

feign微服务间文件上传（Finchley版本）

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。

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。