[Java的写法]之MD5对字符串签名操作

对字符串签名后，1：长字符串变为32位字符：aacfbe08d042fddd8ee778b148efc923 2 ： 只要长字符串内容不变，签名后得到的32位字符不变。适合用来做ID等。 private String genKeyId(String keyStr) { return Md5Utils.getStringMD5(keyStr); }

Md5Utils 类如下：

1import java.io.File;
2import java.io.FileInputStream;
3import java.io.IOException;
4import java.io.InputStream;
5import java.security.MessageDigest;
6import java.security.NoSuchAlgorithmException;
7import org.apache.commons.lang3.StringUtils;
8
9public class Md5Utils {
10    protected static char[] hexDigits = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
11    protected static MessageDigest messagedigest = null;
12
13    public Md5Utils() {      }
14    static {
15        try {
16            messagedigest = MessageDigest.getInstance("MD5");
17        } catch (NoSuchAlgorithmException var1) {
18            var1.printStackTrace();
19        }
20
21    }
22
23    public static String getFileMD5String(File file) throws IOException {
24        InputStream fis = new FileInputStream(file);
25        byte[] buffer = new byte[1024];
26        boolean var3 = false;
27
28        int numRead;
29        while((numRead = fis.read(buffer)) > 0) {
30            messagedigest.update(buffer, 0, numRead);
31        }
32
33        fis.close();
34        return bufferToHex(messagedigest.digest());
35    }
36
37    public static String getStringMD5(String str) {
38        if (StringUtils.isEmpty(str)) {
39            return "";
40        } else {
41            byte[] buffer = str.getBytes();
42            messagedigest.update(buffer);
43            return bufferToHex(messagedigest.digest());
44        }
45    }
46
47    public static String bufferToHex(byte[] bytes) {
48        return bufferToHex(bytes, 0, bytes.length);
49    }
50
51    private static String bufferToHex(byte[] bytes, int m, int n) {
52        StringBuffer stringbuffer = new StringBuffer(2 * n);
53        int k = m + n;
54
55        for(int l = m; l < k; ++l) {
56            appendHexPair(bytes[l], stringbuffer);
57        }
58
59        return stringbuffer.toString();
60    }
61
62    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
63        char c0 = hexDigits[(bt & 240) >> 4];
64        char c1 = hexDigits[bt & 15];
65        stringbuffer.append(c0);
66        stringbuffer.append(c1);
67    }
68
69    private static final String toHex(byte[] hash) {
70        if (hash == null) {
71            return null;
72        } else {
73            StringBuffer buf = new StringBuffer(hash.length * 2);
74
75            for(int i = 0; i < hash.length; ++i) {
76                if ((hash[i] & 255) < 16) {
77                    buf.append("0");
78                }
79
80                buf.append(Long.toString((long)(hash[i] & 255), 16));
81            }
82
83            return buf.toString();
84        }
85    }
86
87    public static String hash(String s) {
88        try {
89            return new String(toHex(getStringMD5(s).getBytes("UTF-8")).getBytes("UTF-8"), "UTF-8");
90        } catch (Exception var2) {
91            return s;
92        }
93    }
94
95    public static void main(String[] args) {
96        System.out.println(getStringMD5("admin123"));
97        System.out.println(hash("123456"));
98    }
99
100
101}