inputstream 流复用

public class InputStreamCache {
    /**
     * 将InputStream中的字节保存到ByteArrayOutputStream中。
     */
    private ByteArrayOutputStream byteArrayOutputStream = null;

    public InputStreamCache(InputStream inputStream) {
        if (Objects.isNull(inputStream)) {
            return;
        }
        byteArrayOutputStream = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        try {
            while ((len = inputStream.read(buffer)) > -1) {
                byteArrayOutputStream.write(buffer, 0, len);
            }
            byteArrayOutputStream.flush();
        } catch (IOException e) {
            log.error(e.getMessage(), e);
        }
    }

    public InputStream getInputStream() {
        if (Objects.isNull(byteArrayOutputStream)) {
            return null;
        }
        return new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
    }
}