最近要弄一下Java讀取文件MD5，注意這裡是小文件，網上找了一下，有兩種解決方案，一種是用MessageDigest來實現，另種是用org.apache.commons.codec.digest來實現，代碼如下：
package cdm;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.math.BigInteger;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import org.apache.commons.codec.digest.*;
import org.apache.commons.io.IOUtils;
public class testMD5 {
public static String getMd5ByFile(File file) throws FileNotFoundException {
String value = null;
FileInputStream in = new FileInputStream(file);
try {
MappedByteBuffer byteBuffer = in.getChannel().map(FileChannel.MapMode.READ_ONLY, 0, file.length());
MessageDigest md5 = MessageDigest.getInstance("MD5");
md5.update(byteBuffer);
BigInteger bi = new BigInteger(1, md5.digest());
value = bi.toString(16);
} catch (Exception e) {
e.printStackTrace();
} finally {
if(null != in) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return value;
}
public static void main(String[] args) throws IOException {
String path="E:\\commons-codec-1.9-bin.zip";
String v = getMd5ByFile(new File(path));
System.out.println("MD5:"+v.toUpperCase());
FileInputStream fis= new FileInputStream(path);
String md5 = DigestUtils.md5Hex(IOUtils.toByteArray(fis));
IOUtils.closeQuietly(fis);
System.out.println("MD5:"+md5);
//System.out.println("MD5:"+DigestUtils.md5Hex("WANGQIUYUN"));
}
}
Java實現MD5加密解密類 http://www.linuxidc.com/Linux/2014-06/102732.htm
Java項目中用到的MD5加密 http://www.linuxidc.com/Linux/2014-03/98747.htm
Linux下MD5sum 校驗文件完整性 http://www.linuxidc.com/Linux/2014-03/98416.htm
使用OpenSSL的MD5計算功能 http://www.linuxidc.com/Linux/2013-10/91119.htm
Linux下計算文件的MD5值 http://www.linuxidc.com/Linux/2012-11/74902.htm
運行：
結果在官網提供的MD5一致。
附commons-codec-1.9.jar下載地址：http://commons.apache.org/proper/commons-codec/download_codec.cgi
如果要處理過G的文件，請參照：http://www.linuxidc.com/Linux/2014-09/106397p2.htm