base64转MultipartFile避坑_java base64转multipartfile

需求：接收base64编码的文件，然后上传到文件服务器。

思路：首先将base64转为MultipartFile类型，然后通过feign调用将文件上传至服务器

代码如下：

    @RequestMapping(method = RequestMethod.POST, value = "/doc/file/uploadForAPI",consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    Response docUpload(@RequestPart("file") MultipartFile file,
                   @RequestParam("appCode") String appCode,
                   @RequestParam("fileProp") String fileProp,
                   @RequestParam(value = "folderName",required = false) String folderName) throws Exception;

base64转成对应的MultipartFile，代码如下：

package com.*.product.evidence.storage.model;
 
import org.springframework.web.multipart.MultipartFile;
 
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Base64;
 
/**
 * @author 
 * @date 2022/12/06 16:40
 * @description 转换base64为文件流
 */
public class Base64ToMultipartFile implements MultipartFile {
 
    private final byte[] fileContent;
 
    private final String name;
    private final String extension;
    private final String contentType;
 
    private final String originalFilename;
 
    /**
     * @param base64
     * @param dataUri     格式类似于: data:image/png;base64
     */
    public Base64ToMultipartFile(String base64, String dataUri, String name, String originalfilename) {
        this.fileContent = Base64.getDecoder().decode(base64.getBytes(StandardCharsets.UTF_8));
        this.extension = dataUri.split(";")[0].split("/")[1];
        this.contentType = dataUri.split(";")[0].split(":")[1];
        this.originalFilename = originalfilename;
        this.name = name;
    }
 
    /**
     * 【重要】必须与请求接收方参数名称一致，否则找不到参数
     * @return
     */
    @Override
    public String getName() {
        return this.name;
    }
 
    @Override
    public String getOriginalFilename() {
        return originalFilename;
    }
 
    @Override
    public String getContentType() {
        return contentType;
    }
 
    @Override
    public boolean isEmpty() {
        return fileContent == null || fileContent.length == 0;
    }
 
    @Override
    public long getSize() {
        return fileContent.length;
    }
 
    @Override
    public byte[] getBytes() throws IOException {
        return fileContent;
    }
 
    @Override
    public ByteArrayInputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(fileContent);
    }
 
    @Override
    public void transferTo(File file) throws IOException, IllegalStateException {
        try (FileOutputStream fos = new FileOutputStream(file)) {
            fos.write(fileContent);
        }
    }
 
}

调试后文件服务器报错提示找不到请求参数“file”，经过长时间的排查发现重写的Base64ToMultipartFile类的getName()方法必须返回和接收参数同名的值，即file，否则feign的接收方无法收到对应的参数。

对应的实例化方法：

        MultipartFile file = new Base64ToMultipartFile(data, dataUri, "file", entity.getFileName());