从Message Digest获取MD5字符串

Question

I understand how it works but if I want to print out the MD5 as String how would I do that?

public static void getMD5(String fileName) throws Exception{
    InputStream input =  new FileInputStream(fileName);
    byte[] buffer = new byte[1024];

    MessageDigest hash = MessageDigest.getInstance("MD5");
    int read;
    do {
        read = input.read(buffer);
        if (read > 0) {
            hash.update(buffer, 0, read);
        }
    } while (read != -1);
    input.close();
}

Answer 1

你可以减少写作：

String hex = (new HexBinaryAdapter()).marshal(md5.digest(YOUR_STRING.getBytes()))

Answer 2

    String input = "168";
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] md5sum = md.digest(input.getBytes());
    String output = String.format("%032X", new BigInteger(1, md5sum));

or

DatatypeConverter.printHexBinary( MessageDigest.getInstance("MD5").digest("a".getBytes("UTF-8")))

Answer 3

Try this

StringBuffer hexString = new StringBuffer();
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] hash = md.digest();

for (int i = 0; i < hash.length; i++) {
    if ((0xff & hash[i]) < 0x10) {
        hexString.append("0"
                + Integer.toHexString((0xFF & hash[i])));
    } else {
        hexString.append(Integer.toHexString(0xFF & hash[i]));
    }
}

Answer 4

You can also use Apache Commons Codec library. This library includes methods public static String md5Hex(InputStream data) and public static String md5Hex(byte[] data) in the DigestUtils class. No need to invent this yourself ;)

Answer 5

First you need to get the byte[] output of the MessageDigest :

byte[] bytes = hash.digest();

You can't easily print this though (with eg new String(bytes) ) because it's going to contain binary that won't have good output representations. You can convert it to hex for display like this however:

StringBuilder sb = new StringBuilder(2 * bytes.length);
for (byte b : bytes) {
    sb.append("0123456789ABCDEF".charAt((b & 0xF0) >> 4));
    sb.append("0123456789ABCDEF".charAt((b & 0x0F)));
}
String hex = sb.toString();

Answer 6

With the byte array, result from message digest:

...
byte hashgerado[] = md.digest(entrada);
...

for(byte b : hashgerado)
    System.out.printf("%02x", Byte.toUnsignedInt(b));

Result (for example):
89e8a9f68ad3c4bba9b9d3581cf5201d

Answer 7

/**
 * hashes:
 * e7cfa2be5969e235138356a54bad7fc4
 * 3c9ec110aa171b57bb41fc761130822c
 *
 * compiled with java 8 - 12 Dec 2015
 */
public static String generateHash() {
    long r = new java.util.Random().nextLong();
    String input = String.valueOf(r);
    String md5 = null;

    try {
        java.security.MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
        //Update input string in message digest
        digest.update(input.getBytes(), 0, input.length());
        //Converts message digest value in base 16 (hex)
        md5 = new java.math.BigInteger(1, digest.digest()).toString(16);
    }
    catch (java.security.NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return md5;
}

Answer 8

FYI...

In certain situations this did not work for me

md5 = new java.math.BigInteger(1, digest.digest()).toString(16);

but this did

StringBuilder sb = new StringBuilder();

for (int i = 0; i < digest.length; i++) {
    if ((0xff & digest[i]) < 0x10) {
        sb.append("0").append(Integer.toHexString((0xFF & digest[i])));
    } else {
        sb.append(Integer.toHexString(0xFF & digest[i]));
    }
}

String result = sb.toString();

Answer 9

Shortest way:

String toMD5(String input) {
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] raw = md.digest(input.getBytes());
    return DatatypeConverter.printHexBinary(raw);
}

Just remember to handle the exception.

Answer 10

This is another version of @anything answer:

StringBuilder sb = new StringBuilder();

for (int i = 0; i < digest.length; i++) {
    if ((0xff & digest[i]) < 0x10) {
        sb.append("0").append(Integer.toHexString((0xFF & digest[i])));
    } else {
        sb.append(Integer.toHexString(0xFF & digest[i]));
    }
}

String result = sb.toString();

Answer 11

Call hash.digest() to finish the process. It will return an array of bytes.

You can create a String from a byte[] using a String constructor, however if you want a hex string you'll have to loop through the byte array manually and work out the characters.