MD5Util校验大型文件

 1 import java.io.File;
 2 import java.io.FileInputStream;
 3 import java.io.IOException;
 4 import java.security.MessageDigest;
 5 import java.security.NoSuchAlgorithmException;
 6 import org.springframework.stereotype.Component;
 7 import com.tg.exception.DataValidException;
 8 
 9 @Component
10 public class MD5Util implements IMD5Util {
11     /**
12      * 默认的密码字符串组合，apache校验下载的文件的正确性用的就是默认的这个组合
13      */
14     protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
15     protected static MessageDigest messageDigest = null;
16     static {
17     try {
18         messageDigest = MessageDigest.getInstance("MD5");
19     } catch (NoSuchAlgorithmException e) {
20         System.err.println(MD5Util.class.getName() + "初始化失败，MessageDigest不支持MD5Util.");
21         e.printStackTrace();
22     }
23     }
24 
25     /**
26      * 计算文件的MD5
27      * 
28      * @param fileName
29      *            文件的绝对路径
30      * @return
31      * @throws IOException
32      */
33     public String getFileMD5String(String fileName) throws IOException {
34     File f = new File(fileName);
35     return getFileMD5String(f);
36     }
37 
38     /**
39      * 计算文件的MD5，重载方法
40      * 
41      * @param file
42      *            文件对象
43      * @return
44      * @throws IOException
45      */
46     public String getFileMD5String(File file) throws IOException {
47     if (!file.exists() || !file.isFile()) {
48         throw new DataValidException("不是有效文件！");
49     }
50     FileInputStream in = new FileInputStream(file);
51     byte[] buffer = new byte[1024 * 1024 * 10];
52     int len = 0;
53     while ((len = in.read(buffer)) > 0) {
54         messageDigest.update(buffer, 0, len);
55     }
56     in.close();
57     return bufferToHex(messageDigest.digest());
58     }
59 
60     private String bufferToHex(byte bytes[]) {
61     return bufferToHex(bytes, 0, bytes.length);
62     }
63 
64     private String bufferToHex(byte bytes[], int m, int n) {
65     StringBuffer stringbuffer = new StringBuffer(2 * n);
66     int k = m + n;
67     for (int l = m; l < k; l++) {
68         appendHexPair(bytes[l], stringbuffer);
69     }
70     System.out.println("文件MD5值:" + stringbuffer);
71     return stringbuffer.toString();
72     }
73 
74     private void appendHexPair(byte bt, StringBuffer stringbuffer) {
75     char c0 = hexDigits[(bt & 0xf0) >> 4];
76     char c1 = hexDigits[bt & 0xf];
77     stringbuffer.append(c0);
78     stringbuffer.append(c1);
79     }
80 }

本例参考自http://zhouzaibao.iteye.com/blog/343870与http://hi.baidu.com/chenxiaowen/blog/item/9a9cb6deb5c2e95dccbf1abe.html