Java文件與字節數組轉換
/**
* 返回一個byte數組
* @param file
* @return
* @throws IOException
*/
private byte[] getBytesFromFile(File file){
byte[] bytes = null;
try {
InputStream is = new FileInputStream(file);
// 獲取文件大小
long length = file.length();
if (length > Integer.MAX_VALUE) {
// 文件太大，無法讀取
throw new IOException("File is to large " + file.getName());
}
// 創建一個數據來保存文件數據
bytes = new byte[(int) length];
// 讀取數據到byte數組中
int offset = 0;
int numRead = 0;
while (offset < bytes.length
&& (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {
offset += numRead;
}
// 確保所有數據均被讀取
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;
}
/**
* 文件轉化爲字節數組
*
* @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;
}
/**
* 把字節數組保存爲一個文件
*
* @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;
}