我想使用Java来获得文件的MD5校验和。我真的很惊讶,但我还没有找到任何东西,显示如何获得一个文件的MD5校验和。
这是怎么做到的?
我想使用Java来获得文件的MD5校验和。我真的很惊讶,但我还没有找到任何东西,显示如何获得一个文件的MD5校验和。
这是怎么做到的?
当前回答
非常快速和干净的java方法,不依赖于外部库:
(如果你想要,只需将MD5替换为SHA-1, SHA-256, SHA-384或SHA-512)
public String calcMD5() throws Exception{
byte[] buffer = new byte[8192];
MessageDigest md = MessageDigest.getInstance("MD5");
DigestInputStream dis = new DigestInputStream(new FileInputStream(new File("Path to file")), md);
try {
while (dis.read(buffer) != -1);
}finally{
dis.close();
}
byte[] bytes = md.digest();
// bytesToHex-method
char[] hexChars = new char[bytes.length * 2];
for ( int j = 0; j < bytes.length; j++ ) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
其他回答
标准Java运行时环境方式:
public String checksum(File file) {
try {
InputStream fin = new FileInputStream(file);
java.security.MessageDigest md5er =
MessageDigest.getInstance("MD5");
byte[] buffer = new byte[1024];
int read;
do {
read = fin.read(buffer);
if (read > 0)
md5er.update(buffer, 0, read);
} while (read != -1);
fin.close();
byte[] digest = md5er.digest();
if (digest == null)
return null;
String strDigest = "0x";
for (int i = 0; i < digest.length; i++) {
strDigest += Integer.toString((digest[i] & 0xff)
+ 0x100, 16).substring(1).toUpperCase();
}
return strDigest;
} catch (Exception e) {
return null;
}
}
结果等于linux md5sum实用程序。
使用nio2 (Java 7+),不使用外部库:
byte[] b = Files.readAllBytes(Paths.get("/path/to/file"));
byte[] hash = MessageDigest.getInstance("MD5").digest(b);
将结果与期望的校验和进行比较:
String expected = "2252290BC44BEAD16AA1BF89948472E8";
String actual = DatatypeConverter.printHexBinary(hash);
System.out.println(expected.equalsIgnoreCase(actual) ? "MATCH" : "NO MATCH");
Guava现在提供了一个新的、一致的哈希API,它比JDK中提供的各种哈希API更友好。参见哈希的解释。对于一个文件,你可以很容易地得到MD5和,CRC32(14.0+版本)或许多其他哈希值:
HashCode md5 = Files.hash(file, Hashing.md5());
byte[] md5Bytes = md5.asBytes();
String md5Hex = md5.toString();
HashCode crc32 = Files.hash(file, Hashing.crc32());
int crc32Int = crc32.asInt();
// the Checksum API returns a long, but it's padded with 0s for 32-bit CRC
// this is the value you would get if using that API directly
long checksumResult = crc32.padToLong();
public static String getMd5OfFile(String filePath)
{
String returnVal = "";
try
{
InputStream input = new FileInputStream(filePath);
byte[] buffer = new byte[1024];
MessageDigest md5Hash = MessageDigest.getInstance("MD5");
int numRead = 0;
while (numRead != -1)
{
numRead = input.read(buffer);
if (numRead > 0)
{
md5Hash.update(buffer, 0, numRead);
}
}
input.close();
byte [] md5Bytes = md5Hash.digest();
for (int i=0; i < md5Bytes.length; i++)
{
returnVal += Integer.toString( ( md5Bytes[i] & 0xff ) + 0x100, 16).substring( 1 );
}
}
catch(Throwable t) {t.printStackTrace();}
return returnVal.toUpperCase();
}
public static String MD5Hash(String toHash) throws RuntimeException {
try{
return String.format("%032x", // produces lower case 32 char wide hexa left-padded with 0
new BigInteger(1, // handles large POSITIVE numbers
MessageDigest.getInstance("MD5").digest(toHash.getBytes())));
}
catch (NoSuchAlgorithmException e) {
// do whatever seems relevant
}
}