我在 Internet 上有一个文件的 URL。我需要计算 SHA1 哈希值,并逐行读取该文件。我知道如何做到这一点,但我阅读了该文件两次,这可能不是一个很好的解决方案。
我怎样才能更有效地做到这一点?
这是我的代码:
URL url = new URL(url);
URLConnection urlConnection = url.openConnection();
urlConnection.setConnectTimeout(1000);
urlConnection.setReadTimeout(1000);
logger.error(urlConnection.getContent() + " ");
InputStream is = urlConnection.getInputStream();
// first reading of file is:
int i;
File file = new File("nameOfFile");
BufferedInputStream bis = new BufferedInputStream(is);
BufferedOutputStream bos =
new BufferedOutputStream(new FileOutputStream(file.getName()));
while ((i = bis.read()) != -1) {
bos.write(i);
}
bos.flush();
bis.close();
sha1(file);
// second reading of file is:
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
String line;
while ((line = reader.readLine()) != null) {
// do something
}
protected byte[] sha1(final File file) throws Exception {
if (file == null || !file.exists()) {
return null;
}
final MessageDigest messageDigest = MessageDigest.getInstance(SHA1);
InputStream is = new BufferedInputStream(new FileInputStream(file));
try {
final byte[] buffer = new byte[1024];
for (int read = 0; (read = is.read(buffer)) != -1;) {
messageDigest.update(buffer, 0, read);
}
} finally {
IOUtils.closeQuietly(is);
}
return messageDigest.digest();
}
最佳答案
如果你通过 DigestInputStream
传递它,它将执行 MessageDigest
并且仍可用作 InputStream
。
DigestInputStream dis = new DigestInputStream(is,
MessageDigest.getInstance(SHA1));
BufferedInputStream bis = new BufferedInputStream(dis);
BufferedOutputStream bos = new BufferedOutputStream(
new FileOutputStream(file.getName()));
while ((i = bis.read()) != -1) {
bos.write(i);
}
bos.close();
return dis.getMessageDigest().digest();
关于java - 如何读取和计算互联网上文件的哈希值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17729789/