文件下载，从服务器，输入流

/**
     *
     * @param inputStream 输入流
     * @param filepath 文件输出路径包含完整文件名
     */
    public static void downloadFile(InputStream inputStream,String filepath){
        try {
            FileOutputStream file = new FileOutputStream(filepath);
            int len = (int) inputStream.available();
            byte[] buffer = new byte[len]; // 建立缓冲区
            while ((len = inputStream.read(buffer)) != -1) {
                file.write(buffer, 0, len);
            }
            file.close();
            inputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

文件下载，从数据库，blob
其实同理，只是多了一步操作，将blob转为输入流

/**
     *blob数据存储到本地
     * @param fileBlob blob数据
     * @param filepath 文件输出路径包含完整文件名
     */
    public static void downloadBlob(Blob fileBlob,String filepath){
        try {
            InputStream binaryStream = fileBlob.getBinaryStream();
            FileOutputStream file = new FileOutputStream(filepath);
            int len = (int) fileBlob.length();
            byte[] buffer = new byte[len]; // 建立缓冲区
            while ((len = binaryStream.read(buffer)) != -1) {
                file.write(buffer, 0, len);
            }
            file.close();
            binaryStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }