獲取檔案的md5(java & php)
阿新 • • 發佈:2019-02-02
每個檔案都可以用MD5驗證程式算出一個固定的md5碼來,它是一個檔案的檔案簽名,可用於驗證自己下載的軟體是否為原版。百度網盤的“秒傳”應該也用到了這個,即上傳之前首先計算該檔案的md5值,然後看伺服器上有沒有該檔案,有的話從服務端直接拷貝,節省上傳時間和降低網路負擔。
java的MD5util類:
import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class MD5FileUtil { private static final Logger logger = LoggerFactory .getLogger(MD5FileUtil.class); protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; protected static MessageDigest messagedigest = null; static { try { messagedigest = MessageDigest.getInstance("MD5"); } catch (NoSuchAlgorithmException e) { logger.error("MD5FileUtil messagedigest初始化失敗", e); } } public static String getFileMD5String(File file) throws IOException { FileInputStream in = new FileInputStream(file); FileChannel ch = in.getChannel(); MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length()); messagedigest.update(byteBuffer); return bufferToHex(messagedigest.digest()); } public static String getMD5String(String s) { return getMD5String(s.getBytes()); } public static String getMD5String(byte[] bytes) { messagedigest.update(bytes); return bufferToHex(messagedigest.digest()); } private static String bufferToHex(byte bytes[]) { return bufferToHex(bytes, 0, bytes.length); } private static String bufferToHex(byte bytes[], int m, int n) { StringBuffer stringbuffer = new StringBuffer(2 * n); int k = m + n; for (int l = m; l < k; l++) { appendHexPair(bytes[l], stringbuffer); } return stringbuffer.toString(); } private static void appendHexPair(byte bt, StringBuffer stringbuffer) { char c0 = hexDigits[(bt & 0xf0) >> 4]; char c1 = hexDigits[bt & 0xf]; stringbuffer.append(c0); stringbuffer.append(c1); } public static boolean checkPassword(String password, String md5PwdStr) { String s = getMD5String(password); return s.equals(md5PwdStr); } public static void main(String[] args) throws IOException { long begin = System.currentTimeMillis(); File big = new File("D:\\temp\\jre-7u11-linux-i586.tar.gz"); String md5 = getFileMD5String(big); long end = System.currentTimeMillis(); System.out.println("md5:" + md5); System.out.println("time:" + ((end - begin) / 1000) + "s"); } }
php
例子1:
<?php
$filename = "test.txt";
$md5file = md5_file($filename);
echo $md5file;
?>
會輸出類似下面一串字元:
5d41402abc4b2a76b9719d911017c592
<?php
$md5file = md5_file("test.txt");
file_put_contents("md5file.txt",$md5file);
?>
//在本例中,我們將檢測 "test.txt" 是否已被更改(即是否 MD5 雜湊已被更改):
<?php $md5file = file_get_contents("md5file.txt"); if (md5_file("test.txt") == $md5file) { echo "The file is ok."; } else { echo "The file has been changed."; } ?>
輸出:
The file is ok.