package util;
import java.io.*;
import java.nio.*;
import java.nio.channels.FileChannel;
import java.security.*;
public class MD5Util {
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 nsaex) {
System.err.println(MD5Util.class.getName()
+ "初始化失败,MessageDigest不支持MD5Util。");
nsaex.printStackTrace();
}
}
/**
* 生成字符串的md5校验值
*
* @param s
* @return
*/
public static String getMD5String(String s) {
return getMD5String(s.getBytes());
}
/**
* 判断字符串的md5校验码是否与一个已知的md5码相匹配
*
* @param password 要校验的字符串
* @param md5PwdStr 已知的md5校验码
* @return
*/
public static boolean checkPassword(String password, String md5PwdStr) {
String s = getMD5String(password);
return s.equals(md5PwdStr);
}
/**
* 生成文件的md5校验值
*
* @param file
* @return
* @throws IOException
*/
public static String getFileMD5String(File file) throws IOException {
InputStream fis;
fis = new FileInputStream(file);
byte[] buffer = new byte[1024];
int numRead = 0;
while((numRead = fis.read(buffer)) > 0) {
messageDigest.update(buffer, 0, numRead);
}
fis.close();
return bufferToHex(messageDigest.digest());
}
/**
* * @param file
* @return
* @throws IOException
*/
public static String getFileMD5String_old(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(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[1], stringBuffer);
}
return stringBuffer.toString();
}
private static void appendHexPair(byte bt, StringBuffer stringBuffer) {
char c0 = hexDigits[(bt & 0xf0) >> 4];
// 取字节中高 4 位的数字转换, >>> 为逻辑右移,将符号位一起右移,此处未发现两种符号有何不同
char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换
stringBuffer.append(c0);
stringBuffer.append(c1);
}
public static void main(String[] args) throws IOException {
long begin = System.currentTimeMillis();
File file = new File("D:/in.txt");
String md5 = getFileMD5String(file);
//String md5 = getMD5String("a");
long end = System.currentTimeMillis();
System.out.println("md5: " + md5 + ((end - begin) / 1000) + "s");
}
}
java MD5文件校验工具类
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转载自blog.csdn.net/jjj1299894209/article/details/80842221
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