java  文件流方法：MultipartFile 转 File,File 转byte[]数组，File转String, String 转File

================================MultipartFile 转 File======================================

/**
 * MultipartFile 转 File
 *
 * @param file
 * @throws Exception
 */
public static java.io.File multipartFileToFile(MultipartFile file) {
    java.io.File toFile = null;
    InputStream ins = null;
    try {
        if (file == null || file.getSize() <= 0) {
            file = null;
        } else {

            ins = file.getInputStream();
            toFile = new java.io.File(file.getOriginalFilename());
            inputStreamToFile(ins, toFile);

        }
    } catch (Exception ex) {
        log.error("ERROR:" + ex);
    } finally {
        // TODO update
        IOUtils.closeQuietly(ins);
    }
    return toFile;
}

================================将文件转换成byte数组======================================

/**
 * 将文件转换成byte数组
 * @param file
 * @return
 */
public static byte[] File2byte(File file) {
    byte[] buffer = null;
    try {
        FileInputStream fis = new FileInputStream(file);
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] b = new byte[1024];
        int n;
        while ((n = fis.read(b)) != -1) {
            bos.write(b, 0, n);
        }
        fis.close();
        bos.close();
        buffer = bos.toByteArray();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return buffer;
}

=================================File文件转String======================================

/**
 * File文件转String
 *
 * @param file
 * @return
 * @throws IOException
 */
public String fileToString(java.io.File file) throws IOException {
    if (file.exists()) {
        byte[] data = new byte[(int) file.length()];
        boolean result;
        FileInputStream inputStream = null;
        try {
            inputStream = new FileInputStream(file);
            int len = inputStream.read(data);
            result = len == data.length;
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }
        }
        if (result) {
            return new String(data);
        }
    }
    return null;
}

=================================字符串输出为文件的方法======================================

/**
 * 字符串输出为文件的方法
 *
 * @param fileContent  文件的字符串
 * @param absolutePath 输出路径
 * @return
 */
public boolean stringToFile(String fileContent, String absolutePath) {
    log.info("stringToFile:start");
    boolean result = false;
    java.io.File absolutePathFielName = new java.io.File(absolutePath);
    OutputStream os = null;
    try {
        if (absolutePathFielName.exists()) {
            absolutePathFielName.delete();
        }
        os = new FileOutputStream(absolutePathFielName);
        os.write(fileContent.getBytes());
        os.flush();
        result = true;

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (os != null) {
                os.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    log.info("stringToFile:end");
    return result;
}