在Java中是否有任何方法可以生成一个字符串的MD5哈希?
当前回答
我只是下载了common -codec.jar,得到了完美的php,比如md5。这是手册。
只需将其导入到您的项目并使用即可
String Url = "your_url";
System.out.println( DigestUtils.md5Hex( Url ) );
结果出来了。
其他回答
使用java.security.MessageDigest库的简单函数
public String stringMD5Hash(String text) throws NoSuchAlgorithmException {
MessageDigest messageDigest = MessageDigest.getInstance("MD5");
byte[] bytes = messageDigest.digest(text.getBytes());
StringJoiner stringJoiner = new StringJoiner("");
for (byte b : bytes) {
stringJoiner.add(Integer.toHexString((b & 0xFF) | 0x100).substring(1, 3));
}
return stringJoiner.toString();
}
对于文件使用这个函数
public static String FileMD5Hash(File file) throws NoSuchAlgorithmException, IOException {
MessageDigest messageDigest = MessageDigest.getInstance("MD5");
byte[] bytes = messageDigest.digest(getFileBytes(file));
StringJoiner stringJoiner = new StringJoiner("");
for (byte b : bytes) {
stringJoiner.add(Integer.toHexString((b & 0xFF) | 0x100).substring(1, 3));
}
return stringJoiner.toString();
}
public static byte[] getFileBytes(File file) throws IOException{
InputStream inputStream = new FileInputStream(file);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
byte[] bytes = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(bytes)) != -1) {
byteArrayOutputStream.write(bytes, 0, bytesRead);
}
return byteArrayOutputStream.toByteArray();
}
Bombe的答案是正确的,但请注意,除非你绝对必须使用MD5(例如,为了互操作性而被迫使用),否则更好的选择是SHA1,因为MD5长期使用有缺点。
我应该补充一点,SHA1也有理论上的漏洞,但没有那么严重。目前的哈希技术水平是,有许多候选替换哈希函数,但还没有一个成为取代SHA1的标准最佳实践。因此,根据您的需要,建议您使您的哈希算法可配置,以便将来可以替换它。
是我做的…似乎还行-我相信有人会指出错误…
public final class MD5 {
public enum SaltOption {
BEFORE, AFTER, BOTH, NONE;
}
private static final String ALG = "MD5";
//For conversion to 2-char hex
private static final char[] digits = {
'0' , '1' , '2' , '3' , '4' , '5' ,
'6' , '7' , '8' , '9' , 'a' , 'b' ,
'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
'o' , 'p' , 'q' , 'r' , 's' , 't' ,
'u' , 'v' , 'w' , 'x' , 'y' , 'z'
};
private SaltOption opt;
/**
* Added the SaltOption constructor since everybody
* has their own standards when it comes to salting
* hashes.
*
* This gives the developer the option...
*
* @param option The salt option to use, BEFORE, AFTER, BOTH or NONE.
*/
public MD5(final SaltOption option) {
//TODO: Add Char Encoding options too... I was too lazy!
this.opt = option;
}
/**
*
* Returns the salted MD5 checksum of the text passed in as an argument.
*
* If the salt is an empty byte array - no salt is applied.
*
* @param txt The text to run through the MD5 algorithm.
* @param salt The salt value in bytes.
* @return The salted MD5 checksum as a <code>byte[]</code>
* @throws NoSuchAlgorithmException
*/
private byte[] createChecksum(final String txt, final byte[] salt) throws NoSuchAlgorithmException {
final MessageDigest complete = MessageDigest.getInstance(ALG);
if(opt.equals(SaltOption.BEFORE) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
complete.update(txt.getBytes());
if(opt.equals(SaltOption.AFTER) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
return complete.digest();
}
/**
*
* Returns the salted MD5 checksum of the file passed in as an argument.
*
* If the salt is an empty byte array - no salt is applied.
*
* @param fle The file to run through the MD5 algorithm.
* @param salt The salt value in bytes.
* @return The salted MD5 checksum as a <code>byte[]</code>
* @throws IOException
* @throws NoSuchAlgorithmException
*/
private byte[] createChecksum(final File fle, final byte[] salt)
throws IOException, NoSuchAlgorithmException {
final byte[] buffer = new byte[1024];
final MessageDigest complete = MessageDigest.getInstance(ALG);
if(opt.equals(SaltOption.BEFORE) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
int numRead;
InputStream fis = null;
try {
fis = new FileInputStream(fle);
do {
numRead = fis.read(buffer);
if (numRead > 0) {
complete.update(buffer, 0, numRead);
}
} while (numRead != -1);
} finally {
if (fis != null) {
fis.close();
}
}
if(opt.equals(SaltOption.AFTER) || opt.equals(SaltOption.BOTH)) {
complete.update(salt);
}
return complete.digest();
}
/**
*
* Efficiently converts a byte array to its 2 char per byte hex equivalent.
*
* This was adapted from JDK code in the Integer class, I just didn't like
* having to use substrings once I got the result...
*
* @param b The byte array to convert
* @return The converted String, 2 chars per byte...
*/
private String convertToHex(final byte[] b) {
int x;
int charPos;
int radix;
int mask;
final char[] buf = new char[32];
final char[] tmp = new char[3];
final StringBuilder md5 = new StringBuilder();
for (int i = 0; i < b.length; i++) {
x = (b[i] & 0xFF) | 0x100;
charPos = 32;
radix = 1 << 4;
mask = radix - 1;
do {
buf[--charPos] = digits[x & mask];
x >>>= 4;
} while (x != 0);
System.arraycopy(buf, charPos, tmp, 0, (32 - charPos));
md5.append(Arrays.copyOfRange(tmp, 1, 3));
}
return md5.toString();
}
/**
*
* Returns the salted MD5 checksum of the file passed in as an argument.
*
* @param fle The file you want want to run through the MD5 algorithm.
* @param salt The salt value in bytes
* @return The salted MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final File fle, final byte[] salt)
throws NoSuchAlgorithmException, IOException {
return convertToHex(createChecksum(fle, salt));
}
/**
*
* Returns the MD5 checksum of the file passed in as an argument.
*
* @param fle The file you want want to run through the MD5 algorithm.
* @return The MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final File fle)
throws NoSuchAlgorithmException, IOException {
return convertToHex(createChecksum(fle, new byte[0]));
}
/**
*
* Returns the salted MD5 checksum of the text passed in as an argument.
*
* @param txt The text you want want to run through the MD5 algorithm.
* @param salt The salt value in bytes.
* @return The salted MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final String txt, final byte[] salt)
throws NoSuchAlgorithmException {
return convertToHex(createChecksum(txt, salt));
}
/**
*
* Returns the MD5 checksum of the text passed in as an argument.
*
* @param txt The text you want want to run through the MD5 algorithm.
* @return The MD5 checksum as a 2 char per byte HEX <code>String</code>
* @throws NoSuchAlgorithmException
* @throws IOException
*/
public String getMD5Checksum(final String txt)
throws NoSuchAlgorithmException {
return convertToHex(createChecksum(txt, new byte[0]));
}
}
我不知道这与阅读这篇文章的人是否相关,但我只是遇到了我想要解决的问题
从给定的URL下载文件和 将其MD5值与已知值进行比较。
我希望只使用JRE类(没有Apache Commons或类似的类)。我在网上快速搜索了一下,并没有看到同时执行这两项任务的示例代码片段,只是分别执行了每项任务。因为这需要读取相同的文件两次,所以我认为有必要编写一些代码来统一这两个任务,在下载文件时实时计算校验和。这是我的结果(如果它不是完美的Java,很抱歉,但我猜你已经明白了):
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.net.URL;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.security.DigestOutputStream; // new
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
void downloadFile(String fromURL, String toFile, BigInteger md5)
throws IOException, NoSuchAlgorithmException
{
ReadableByteChannel in = Channels.newChannel(new URL(fromURL).openStream());
MessageDigest md5Digest = MessageDigest.getInstance("MD5");
WritableByteChannel out = Channels.newChannel(
//new FileOutputStream(toFile)); // old
new DigestOutputStream(new FileOutputStream(toFile), md5Digest)); // new
ByteBuffer buffer = ByteBuffer.allocate(1024 * 1024); // 1 MB
while (in.read(buffer) != -1) {
buffer.flip();
//md5Digest.update(buffer.asReadOnlyBuffer()); // old
out.write(buffer);
buffer.clear();
}
BigInteger md5Actual = new BigInteger(1, md5Digest.digest());
if (! md5Actual.equals(md5))
throw new RuntimeException(
"MD5 mismatch for file " + toFile +
": expected " + md5.toString(16) +
", got " + md5Actual.toString(16)
);
}
MessageDigest类可以为您提供MD5摘要的实例。
当使用字符串和加密类时,请确保始终指定您希望字节表示的编码。如果只使用string.getBytes(),它将使用平台默认值。(并非所有平台都使用相同的默认值)
import java.security.*;
..
byte[] bytesOfMessage = yourString.getBytes("UTF-8");
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] theMD5digest = md.digest(bytesOfMessage);
如果你有很多数据,看看.update(xxx)方法,它可以被重复调用。然后调用.digest()来获得结果散列。
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