Java文件与字节数组转换

/**

* 返回一个byte数组

* @param file

* @return

* @throws IOException

*/

private byte[] getBytesFromFile(File file){

byte[] bytes = null;

try {

InputStream is = new FileInputStream(file);

// 获取文件大小

long length = file.length();

if (length > Integer.MAX_VALUE) {

// 文件太大，无法读取

throw new IOException("File is to large " + file.getName());

}

// 创建一个数据来保存文件数据

bytes = new byte[(int) length];

// 读取数据到byte数组中

int offset = 0;

int numRead = 0;

while (offset < bytes.length

&& (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {

offset += numRead;

}

// 确保所有数据均被读取

if (offset < bytes.length) {

throw new IOException("Could not completely read file "

+ file.getName());

}

// Close the input stream and return bytes

is.close();

} catch (Exception e) {

e.printStackTrace();

}

return bytes;

}

/**

* 文件转化为字节数组

*

* @param file

* @return

*/

public static byte[] getBytesFromFile(File file) {

byte[] ret = null;

try {

if (file == null) {

// log.error("helper:the file is null!");

return null;

}

FileInputStream in = new FileInputStream(file);

ByteArrayOutputStream out = new ByteArrayOutputStream(4096);

byte[] b = new byte[4096];

int n;

while ((n = in.read(b)) != -1) {

out.write(b, 0, n);

}

in.close();

out.close();

ret = out.toByteArray();

} catch (IOException e) {

// log.error("helper:get bytes from file process error!");

e.printStackTrace();

}

return ret;

}

/**

* 把字节数组保存为一个文件

*

* @param b

* @param outputFile

* @return

*/

public static File getFileFromBytes(byte[] b, String outputFile) {

File ret = null;

BufferedOutputStream stream = null;

try {

ret = new File(outputFile);

FileOutputStream fstream = new FileOutputStream(ret);

stream = new BufferedOutputStream(fstream);

stream.write(b);

} catch (Exception e) {

// log.error("helper:get file from byte process error!");

e.printStackTrace();

} finally {

if (stream != null) {

try {

stream.close();

} catch (IOException e) {

// log.error("helper:get file from byte process error!");

e.printStackTrace();

}

}

}

return ret;

}