将文件读入到字节数组

/**
* 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;
}