我想使用Java来获得文件的MD5校验和。我真的很惊讶,但我还没有找到任何东西,显示如何获得一个文件的MD5校验和。
这是怎么做到的?
我想使用Java来获得文件的MD5校验和。我真的很惊讶,但我还没有找到任何东西,显示如何获得一个文件的MD5校验和。
这是怎么做到的?
当前回答
public static String getMd5OfFile(String filePath)
{
String returnVal = "";
try
{
InputStream input = new FileInputStream(filePath);
byte[] buffer = new byte[1024];
MessageDigest md5Hash = MessageDigest.getInstance("MD5");
int numRead = 0;
while (numRead != -1)
{
numRead = input.read(buffer);
if (numRead > 0)
{
md5Hash.update(buffer, 0, numRead);
}
}
input.close();
byte [] md5Bytes = md5Hash.digest();
for (int i=0; i < md5Bytes.length; i++)
{
returnVal += Integer.toString( ( md5Bytes[i] & 0xff ) + 0x100, 16).substring( 1 );
}
}
catch(Throwable t) {t.printStackTrace();}
return returnVal.toUpperCase();
}
其他回答
在Real的Java-How-to中有一个使用MessageDigest类的例子。
请查看该页面中使用CRC32和SHA-1的示例。
import java.io.*;
import java.security.MessageDigest;
public class MD5Checksum {
public static byte[] createChecksum(String filename) throws Exception {
InputStream fis = new FileInputStream(filename);
byte[] buffer = new byte[1024];
MessageDigest complete = MessageDigest.getInstance("MD5");
int numRead;
do {
numRead = fis.read(buffer);
if (numRead > 0) {
complete.update(buffer, 0, numRead);
}
} while (numRead != -1);
fis.close();
return complete.digest();
}
// see this How-to for a faster way to convert
// a byte array to a HEX string
public static String getMD5Checksum(String filename) throws Exception {
byte[] b = createChecksum(filename);
String result = "";
for (int i=0; i < b.length; i++) {
result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );
}
return result;
}
public static void main(String args[]) {
try {
System.out.println(getMD5Checksum("apache-tomcat-5.5.17.exe"));
// output :
// 0bb2827c5eacf570b6064e24e0e6653b
// ref :
// http://www.apache.org/dist/
// tomcat/tomcat-5/v5.5.17/bin
// /apache-tomcat-5.5.17.exe.MD5
// 0bb2827c5eacf570b6064e24e0e6653b *apache-tomcat-5.5.17.exe
}
catch (Exception e) {
e.printStackTrace();
}
}
}
下面是一个方便的变体,它利用了Java 9中的InputStream.transferTo()和Java 11中的OutputStream.nullOutputStream()。它不需要外部库,也不需要将整个文件加载到内存中。
public static String hashFile(String algorithm, File f) throws IOException, NoSuchAlgorithmException {
MessageDigest md = MessageDigest.getInstance(algorithm);
try(BufferedInputStream in = new BufferedInputStream((new FileInputStream(f)));
DigestOutputStream out = new DigestOutputStream(OutputStream.nullOutputStream(), md)) {
in.transferTo(out);
}
String fx = "%0" + (md.getDigestLength()*2) + "x";
return String.format(fx, new BigInteger(1, md.digest()));
}
and
hashFile("SHA-512", Path.of("src", "test", "resources", "some.txt").toFile());
返回
"e30fa2784ba15be37833d569280e2163c6f106506dfb9b07dde67a24bfb90da65c661110cf2c5c6f71185754ee5ae3fd83a5465c92f72abd888b03187229da29"
从其他答案中提取想法,这里有一个简单的代码,没有第三方依赖关系(或DatatypeConverter,在最新的jdk中更长),将其生成为与md5sum工具输出兼容的十六进制字符串:
import java.io.IOException;
import java.math.BigInteger;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
...
static String calculateMD5(String path) throws IOException
{
try {
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(Files.readAllBytes(Paths.get(path)));
return String.format("%032x", new BigInteger(1, md.digest())); // hex, padded to 32 chars
} catch (NoSuchAlgorithmException ex)
{
throw new RuntimeException(ex); // MD5 is always available so this should be impossible
}
}
有一个输入流装饰器,java。security。DigestInputStream,这样您就可以像往常一样在使用输入流时计算摘要,而不必对数据进行额外的传递。
MessageDigest md = MessageDigest.getInstance("MD5");
try (InputStream is = Files.newInputStream(Paths.get("file.txt"));
DigestInputStream dis = new DigestInputStream(is, md))
{
/* Read decorated stream (dis) to EOF as normal... */
}
byte[] digest = md.digest();
使用nio2 (Java 7+),不使用外部库:
byte[] b = Files.readAllBytes(Paths.get("/path/to/file"));
byte[] hash = MessageDigest.getInstance("MD5").digest(b);
将结果与期望的校验和进行比较:
String expected = "2252290BC44BEAD16AA1BF89948472E8";
String actual = DatatypeConverter.printHexBinary(hash);
System.out.println(expected.equalsIgnoreCase(actual) ? "MATCH" : "NO MATCH");