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Spring Cloud中FeignClient实现文件上传功能

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项目概况:Spring Cloud搭的微服务,使用了eureka,FeignClient,现在遇到FeignClient调用接口时不支持上传文件,

百度到两种方案,一种是使用feign-form和feign-form-spring库来做,源码地址

具体的使用方法是加入maven依赖

<dependency>
 <groupId>io.github.openfeign.form</groupId>
 <artifactId>feign-form-spring</artifactId>
 <version>3.2.2</version>
 </dependency>
 <dependency>
 <groupId>io.github.openfeign.form</groupId>
 <artifactId>feign-form</artifactId>
 <version>3.2.2</version>
</dependency>

注入SpringFormEncoder类

@Bean
 @Primary
 @Scope("prototype")
 public Encoder multipartFormEncoder() {
 return new SpringFormEncoder();
 }

FeignClient接口里方法参数是文件类型的要用@RequestPart注解,且要设置ContentType为multipart/form-data

@ResponseBody
@RequestMapping(value = "/ctstestcase/updateTestCase", method = {RequestMethod.POST}, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
 Map<String, Object> updateTestCase(@RequestParam("testcaseId") String testcaseId,
 @RequestParam("name") String name, @RequestParam("assignId") String assignId,
 @RequestParam("areaId") String areaId, @RequestParam("state") Integer state,
 @RequestParam("iterationId") String iterationId,@RequestParam("priority") Integer priority,
 @RequestParam("moduleId") String moduleId, @RequestParam("executionType") Integer executionType,
 @RequestParam("summary") String summary, @RequestParam("tcsteps") String tcsteps,
 @RequestParam("relations") String relations,@RequestParam("attachments") String attachments,
 @RequestPart("files") MultipartFile[] files);

但遇到一个问题,就是不支持文件数组类型,我看了源码,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:

@FieldDefaults(level = PRIVATE, makeFinal = true)
public class SpringManyMultipartFilesWriter extends AbstractWriter {
 
 SpringSingleMultipartFileWriter fileWriter = new SpringSingleMultipartFileWriter();
 
 @Override
 public void write (Output output, String boundary, String key, Object value) throws Exception {
 if (value instanceof MultipartFile[]) {
 val files = (MultipartFile[]) value;
 for (val file : files) {
 fileWriter.write(output, boundary, key, file);
 }
 } else if (value instanceof Iterable) {
 val iterable = (Iterable<?>) value;
 for (val file : iterable) {
 fileWriter.write(output, boundary, key, file);
 }
 }
 }
 
 @Override
 public boolean isApplicable (Object value) {
 if (value == null) {
 return false;
 }
 if (value instanceof MultipartFile[]) {
 return true;
 }
 if (value instanceof Iterable) {
 val iterable = (Iterable<?>) value;
 val iterator = iterable.iterator();
 if (iterator.hasNext() && iterator.next() instanceof MultipartFile) {
 return true;
 }
 }
 return false;
 }

SpringFormEncoder源码:

public class SpringFormEncoder extends FormEncoder {
 
 /**
 * Constructor with the default Feign's encoder as a delegate.
 */
 public SpringFormEncoder () {
 this(new Encoder.Default());
 }
 
 /**
 * Constructor with specified delegate encoder.
 *
 * @param delegate delegate encoder, if this encoder couldn't encode object.
 */
 public SpringFormEncoder (Encoder delegate) {
 super(delegate);
 
 val processor = (MultipartFormContentProcessor) getContentProcessor(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)) {
 super.encode(object, bodyType, template);
 return;
 }
 
 val file = (MultipartFile) object;
 val data = 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,这就比较奇怪了,底层有对数组的支持但上层却缺少了相应判断,而且在源码里的test包里也没有对文件数组类型的测试,难道只是encode方法里漏掉了?还是说那个文件数组的支持有问题?所以encode方法里才没有加入对其的判断?

于是我先试着对encode方法进行扩展加入对文件数组的判断,应该就可以支持文件数组的上传了,于是把SpringFormEncoder类源码复制出来重命名为FeignSpringFormEncoder,源码如下:

public class FeignSpringFormEncoder extends FormEncoder {
 
 /**
 * Constructor with the default Feign's encoder as a delegate.
 */
 public FeignSpringFormEncoder() {
 this(new Encoder.Default());
 }
 
 
 /**
 * Constructor with specified delegate encoder.
 *
 * @param delegate delegate encoder, if this encoder couldn't encode object.
 */
 public FeignSpringFormEncoder(Encoder delegate) {
 super(delegate);
 
 val processor = (MultipartFormContentProcessor) getContentProcessor(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)) {
 val file = (MultipartFile) object;
 val data = singletonMap(file.getName(), object);
 super.encode(data, MAP_STRING_WILDCARD, template);
 return;
 } else if (bodyType.equals(MultipartFile[].class)) {
 val file = (MultipartFile[]) object;
 if(file != null) {
 val data = singletonMap(file.length == 0 ? "" : file[0].getName(), object);
 super.encode(data, MAP_STRING_WILDCARD, template);
 return;
 }
 }
 super.encode(object, bodyType, template);
 }
}

经过测试,已经可以支持文件数组了,完美解决。

这里再顺便说一下当时还百度到另一个解决文件上传的方案,这个方案就不细说了,直接上我用到的那个开源代码的地址

这个我试过也是可以解决文件上传问题的,但问题是FeignClient不能用SpringMVC的注解,得用Feign自带的注解,也因此我才扩展了第一种方法来做的文件上传功能。

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