inputStream、File、Byte、String等等之间的相互转换

一：inputStream转换

1、inputStream转为byte

//方法一  org.apache.commons.io.IOUtils包下的实现（建议）
IOUtils.toByteArray(inputStream);
//方法二  用java代码实现（其实就是对上面方法一的解析）
public static byte[] toByteArray(InputStream input) throws IOException {
    ByteArrayOutputStream output = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int n = 0;
    while (-1 != (n = input.read(buffer))) {
        output.write(buffer, 0, n);
    }
    return output.toByteArray();
}

2、inputStream转为file

    public static void inputstreamtofile(InputStream ins, File file) throws IOException {
        OutputStream os = new FileOutputStream(file);
        int bytesRead;
        byte[] buffer = new byte[8192];
        while ((bytesRead = ins.read(buffer, 0, 8192)) != -1) {
            os.write(buffer, 0, bytesRead);
        }
        os.close();
        ins.close();
    }

3、inputStream转为String

//方法一  使用org.apache.commons.io.IOUtils包下的方法
IOUtils.toString(inputStream);

//方法二
    /**
     * 将InputStream转换成某种字符编码的String
     *
     * @param in
     * @param encoding
     * @return
     * @throws Exception
     */
    public static String inputStreamToString(InputStream in, String encoding) {
        String string = null;
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        byte[] data = new byte[BUFFER_SIZE];
        int count = -1;
        try {
            while ((count = in.read(data, 0, BUFFER_SIZE)) != -1)
                outStream.write(data, 0, count);
        } catch (IOException e) {
            logger.error("io异常", e.fillInStackTrace());
        }

        try {
            string = new String(outStream.toByteArray(), encoding);
        } catch (UnsupportedEncodingException e) {
            logger.error("字符串编码异常", e.fillInStackTrace());
        }
        return string;
    }

二：byte[]转换

1、byte[]转为inputStream

InputStream sbs = new ByteArrayInputStream(byte[] buf); 

2、byte[]转为File

  public static void byte2File(byte[] buf, String filePath, String fileName)
    {
        BufferedOutputStream bos = null;
        FileOutputStream fos = null;
        File file = null;
        try
        {
            File dir = new File(filePath);
            if (!dir.exists() && dir.isDirectory())
            {
                dir.mkdirs();
            }
            file = new File(filePath + File.separator + fileName);
            fos = new FileOutputStream(file);
            bos = new BufferedOutputStream(fos);
            bos.write(buf);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            if (bos != null)
            {
                try
                {
                    bos.close();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
            if (fos != null)
            {
                try
                {
                    fos.close();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
        }
    }

3、byte[]转String

//先将byte[]转为inputStream,然后在转为String
InputStream is = new ByteArrayInputStream(byte[] byt);
//然后在根据上文提到的将inputStream转为String的方法去转换

三、File的转换

1、file转inputStream

FileInputStream fileInputStream = new FileInputStream(file);