base64图片流转为MultipartFile文件 java后台

MultipartFile是spring框架中的接口，需要自己写一个实现类。代码如下：

public class BASE64DecodedMultipartFile implements MultipartFile {

    private final byte[] imgContent;
    private final String header;

    public BASE64DecodedMultipartFile(byte[] imgContent, String header) {
        this.imgContent = imgContent;
        this.header = header.split(";")[0];
    }

    @Override
    public String getName() {
        // TODO - implementation depends on your requirements
        return System.currentTimeMillis() + Math.random() + "." + header.split("/")[1];
    }

    @Override
    public String getOriginalFilename() {
        // TODO - implementation depends on your requirements
        return System.currentTimeMillis() + (int)Math.random() * 10000 + "." + header.split("/")[1];
    }

    @Override
    public String getContentType() {
        // TODO - implementation depends on your requirements
        return header.split(":")[1];
    }

    @Override
    public boolean isEmpty() {
        return imgContent == null || imgContent.length == 0;
    }

    @Override
    public long getSize() {
        return imgContent.length;
    }

    @Override
    public byte[] getBytes() throws IOException {
        return imgContent;
    }

    @Override
    public InputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(imgContent);
    }

    @Override
    public void transferTo(File dest) throws IOException, IllegalStateException {
        new FileOutputStream(dest).write(imgContent);
    }
       
    
    public static MultipartFile base64ToMultipart(String base64) {
      try {
        String[] baseStrs = base64.split(",");

        BASE64Decoder decoder = new BASE64Decoder();
        byte[] b = new byte[0];
        b = decoder.decodeBuffer(baseStrs[1]);

        for(int i = 0; i < b.length; ++i) {
            if (b[i] < 0) {
                b[i] += 256;
            }
        }
        return new BASE64DecodedMultipartFile(b, baseStrs[0]);
      } catch (IOException e) {
        e.printStackTrace();
        return null;
      }
   }

}

用法：

//"data:image/png;base64," 这个头规则加到base64上后，就可以直接显示到网页上了
String avatar = "data:image/png;base64," + "base64图片字符串";
MultipartFile file = BASE64DecodedMultipartFile.base64ToMultipart(avatar);
//得到输入流
InputStream inputStream = file.getInputStream();
得到流就可以保存或传输了

有不对的地方欢迎留言。