File转成MultipartFile(base64转成MultipartFile)

文章以png为例

图片转base64可以参考:https://blog.csdn.net/qq_36138652/article/details/102664141

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;
        }
    }


    public static String getBase64(String path){
        File file = new File(path);
        String base64 = null;
        try {
            BufferedImage image = ImageIO.read(file);
            Integer width = image.getWidth();
            Integer height = image.getHeight();
            System.out.println("宽：" + width + " 高:"+height);

            //输出流
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            ImageIO.write(image, "png", stream);
            base64 = Base64.encode(stream.toByteArray());
            System.out.println(base64);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return base64;
    }
}

验证:

 public static void main(String[] args) {
        String outPath = "d:/codes/abc1.png";
        String baseImg = BASE64DecodedMultipartFile.getBase64(outPath);
        //这个地方那个一定要特别注意,必须要加上这个开头解析,不同的文件/图片base64都不一样的
        baseImg = "data:image/png;base64,"+baseImg;
        System.out.println("base图片:"+baseImg);
        //成功转成
        MultipartFile multipartFile = BASE64DecodedMultipartFile.base64ToMultipart(baseImg);
    }