Maven creates and checks MD5 checksums at various times. For instance, when downloading an artifact from a repository, Maven checks whether the checksum of the downloaded files (e.g. POM, JAR) is correct.
I am uploading Maven artifactsmanually to a very simple, file-based repository. This requires me to calculate the Maven checksum for artifacts manually.
What sounds like a simple problem at first actually turned out to be quite tricky (as it often does with Maven? Well, I guess it’s still better than regular expressions!).
After digging around in the project checksum-maven-plugin , I finally figured out how to generate MD5 checksum files in a way that Maven will accept. The key here was to use the Hex class from Bouncy Castle to turn the MD5 digest into a String.
Following the rough-cut code to create a hash file for Maven (extracted from the maven-tools project, class WriteHashes ):
public static void writeMd5(final Path baseFile) throws NoSuchAlgorithmException, IOException { final FileInputStream fis = new FileInputStream(baseFile.toFile()); final MessageDigest messageDigest = MessageDigest.getInstance("MD5"); messageDigest.reset(); final byte[] buffer = new byte[1024]; int size = fis.read(buffer, 0, 1024); while (size >= 0) { messageDigest.update(buffer, 0, size); size = fis.read(buffer, 0, 1024); } final String result = new String(Hex.encode(messageDigest.digest())); fis.close(); final Path md5File = baseFile.getFileSystem().getPath(baseFile.toString() + ".md5"); FilesJre.wrap(md5File.toFile()).setText(result); }
