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：
@SpringBootApplicationpublic 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
@Configurationpublic 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
@RestControllerpublic 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：
@SpringBootApplicationpublic 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
@RestControllerpublic 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
@Configurationpublic 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武林网。
新闻热点
疑难解答
