Hashing to string java

How to Generate MD5 Hash in Java — String Byte Array Digest Example

There are multiple ways to generate the MD5 hash in Java program. Not only Java API provides a convenient method for generating MD5 hash, you can also use popular open-source frameworks like Spring and Apache commons Codec to generate MD5 digest in Java. MD5 is a popular Message-Digest Algorithm, which is most commonly used to check data integrity e.g. comparing MD5 checksum to see, if any file is altered or not. Though MD5 has not considered a good cryptographic algorithm for security purposes due to several vulnerabilities found on it, it’s still good enough or checking the integrity of the file. MD5 hashing algorithm generates a 128 bit or 16-byte long hash value.

MD5 hash values, also known as MD5 digest is mostly represented as 32 character Hex String. You can generate an MD5 hash from a byte array, or String directly using Java, Spring and Apache commons-codec.

Spring and Apache commons-codec has identical API e.g. class name DigestUtil s is the same and allows you to directly generate MD5 hash as Hex String, while if you use Java then you need to convert byte array to Hex String, as java.security.MessageDigest.digest() method returns MD5 hash as a byte array.

Earlier we have seen , How to encode and decode String in base64 encoding, an d In this Java tutorial we will see, How to generate an MD5 hash or digest using Java, Spring, and Apache commons code library.

How to Generate MD5 hash in Java — example

In this part, we will see some examples to generate the MD5 hash in Java. Following Java program generates MD5 hash or digest of a String, by converting into a byte array. Java Security package provides MessageDigest, which can generate the MD5 hash.

MessageDigest’s digest() method accepts a byte array and return a byte array of hash value. Since many times we need MD5 hash as Hex String, I have converted that byte array int o Hex String. Apart fr om core Java example, which doesn’t use any dependency, there are a couple of more open-source solution of generating the MD5 digest.

Two of the most popular open source library, Apache Commons Codec and Spring Framework provides utility method to create MD5 Hash in both byte array and Hex String format. Both Apache commons code and Spring provides, DigestUtils class with overloaded method md5() and md5Hex() , which can accept e ither String or by te array and can return either 16 element byte array or 32 characters Hex String.

If you are already using either Spring or Apache Commons-Codec, then it’s best to use DigestUtil , as it only needs a line of code to generate the MD5 hash in Java. here is a complete code example of generating an MD5 digest in Java.

import java.io.UnsupportedEncodingException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.logging.Level; import java.util.logging.Logger; import org.apache.commons.codec.digest.DigestUtils; /** * Java program to generate MD5 hash or digest for String. In this example * we will see 3 ways to create MD5 hash or digest using standard Java API, * Spring framework and open source library, Apache commons codec utilities. * Generally MD5 has are represented as Hex String so each of this function * will return MD5 hash in hex format. * * @author Javin Paul */ public class MD5Hash < public static void main(String args[]) < String password = "password"; System.out.println("MD5 hash generated using Java : " + md5Java(password)); System.out.println("MD5 digest generated using : " + md5Spring(password)); System.out.println("MD5 message created by Apache commons codec : " + md5ApacheCommonsCodec(password)); > public static String md5Java(String message)< String digest = null; try < MessageDigest md = MessageDigest.getInstance("MD5"); byte[] hash = md.digest(message.getBytes("UTF-8")); //converting byte array to Hexadecimal String StringBuilder sb = new StringBuilder(2*hash.length); for(byte b : hash)< sb.append(String.format("%02x", b&0xff)); > digest = sb.toString(); > catch (UnsupportedEncodingException ex) < Logger.getLogger(StringReplace.class.getName()).log(Level.SEVERE, null, ex); > catch (NoSuchAlgorithmException ex) < Logger.getLogger(StringReplace.class.getName()).log(Level.SEVERE, null, ex); > return digest; > /* * Spring framework also provides overloaded md5 methods. You can pass input * as String or byte array and Spring can return hash or digest either as byte * array or Hex String. Here we are passing String as input and getting * MD5 hash as hex String. */ public static String md5Spring(String text)< return DigestUtils.md5Hex(text); > /* * Apache commons code provides many overloaded methods * to generate md5 hash. It contains * md5 method which can accept String, byte[] or InputStream * and can return hash as 16 element byte * array or 32 character hex String. */ public static String md5ApacheCommonsCodec(String content)< return DigestUtils.md5Hex(content); > > Output: MD5 hash generated using Java : 5f4dcc3b5aa765d61d8327deb882cf99 MD5 digest generated using : 5f4dcc3b5aa765d61d8327deb882cf99 MD5 message created by Apache commons code : 5f4dcc3b5aa765d61d8327deb882cf99

That’s all on How to generate an MD5 hash or digest in Java. As you have seen, there is more than one way to generate an MD5 digest, both in a byte array as well as Hex String format. Just remember to specify file encoding to String.getBytes() method, until you have not used any application-wide character encoding.

String.getBytes() uses the platform-specific encoding which could be different in your windows development machine and production Linux Server. Also, consider using Spring or Apache Commons Code to generate MD5 Hash value, if you are already using these libraries. It’s always best to reuse library code than writing your own MD5 hash function, to avoid testing overhead.

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MD5 Hashing in Java

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1. Overview

MD5 is a widely used cryptographic hash function, which produces a hash of 128 bit.

In this article, we will see different approaches to create MD5 hashes using various Java libraries.

2. MD5 Using MessageDigest Class

There is a hashing functionality in java.security.MessageDigest class. The idea is to first instantiate MessageDigest with the kind of algorithm you want to use as an argument:

MessageDigest.getInstance(String Algorithm)

And then keep on updating the message digest using update() function:

public void update(byte [] input)

The above function can be called multiple times when say you are reading a long file. Then finally we need to use digest() function to generate a hash code:

Below is an example which generates a hash for a password and then verifies it:

@Test public void givenPassword_whenHashing_thenVerifying() throws NoSuchAlgorithmException

Similarly, we can also verify checksum of a file:

@Test public void givenFile_generatingChecksum_thenVerifying() throws NoSuchAlgorithmException, IOException < String filename = "src/test/resources/test_md5.txt"; String checksum = "5EB63BBBE01EEED093CB22BB8F5ACDC3"; MessageDigest md = MessageDigest.getInstance("MD5"); md.update(Files.readAllBytes(Paths.get(filename))); byte[] digest = md.digest(); String myChecksum = DatatypeConverter .printHexBinary(digest).toUpperCase(); assertThat(myChecksum.equals(checksum)).isTrue(); >

We need to be aware, that the MessageDigest is not thread-safe. Consequently, we should use a new instance for every thread.

3. MD5 Using Apache Commons

The org.apache.commons.codec.digest.DigestUtils class makes things much simpler.

Let’s see an example for hashing and verifying password:

@Test public void givenPassword_whenHashingUsingCommons_thenVerifying()

4. MD5 Using Guava

Below is another approach we can follow to generate MD5 checksums using com.google.common.io.Files.hash :

@Test public void givenFile_whenChecksumUsingGuava_thenVerifying() throws IOException < String filename = "src/test/resources/test_md5.txt"; String checksum = "5EB63BBBE01EEED093CB22BB8F5ACDC3"; HashCode hash = com.google.common.io.Files .hash(new File(filename), Hashing.md5()); String myChecksum = hash.toString() .toUpperCase(); assertThat(myChecksum.equals(checksum)).isTrue(); >

Note, that Hashing.md5 is deprecated. However, as the official documentation indicates, the reason is rather to advise not to use MD5 in general for security concerns. This means we can still use this method if we, for example, need to integrate with the legacy system that requires MD5. Otherwise, we’re better off considering safer options, like SHA-256.

5. Conclusion

There are different ways in Java API and other third-party APIs like Apache commons and Guava to generate the MD5 hash. Choose wisely based on the requirements of the project and dependencies your project needs to follow.

As always, the code is available over on Github.

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The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

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Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

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