java获取文件md5值

Java中获取文件MD5值的方法有多种。其中，可以使用Apache的commons-codec库、Junit测试框架或Java原生的MessageDigest类来实现。

方法一：使用Apache的commons-codec库

import org.apache.commons.codec.digest.DigestUtils;
import java.io.File;
import java.io.FileInputStream;

File file = new File("d:/test1.jpg");
String md5 = DigestUtils.md5Hex(new FileInputStream(file));
System.out.println(md5);

方法二：使用Junit测试框架

import org.junit.Assert;
import org.junit.Test;
import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;

@Test
public void test_getFileMD5() throws Exception{
    String filepath = "D:\\download\\3_尚学堂_UML概览.avi";
    String md5_1 = SystemUtil.getFileMD5(filepath);
    System.out.println(md5_1);
    byte[] bytes = FileUtils.readFileToByteArray(new File(filepath));
    byte[] md5 = SystemUtil.encryptMD5(bytes);
    String md5_2 = SystemUtil.toHexString(md5);
    System.out.println(md5_2);
    Assert.assertEquals(md5_1, md5_2);
}

方法三：使用Java原生的MessageDigest类

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.math.BigInteger;

File file = new File("d:/test1.jpg");
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 (NoSuchAlgorithmException | IOException e) {
    e.printStackTrace();
} finally {
    if (null != in) {
        try {
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
System.out.println(value);