IdGenerator.java

package eu.europeana.cloud.service.uis.encoder;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.apache.commons.codec.binary.Base32;

/**
 * IdGenerator generate unique id. The characters consists of Base32 dictionary.
 * The implementation ensures that the same input will generate the same result
 * and that the output will always be 52 characters.
 */
public class IdGenerator {

    /**
     * Encode a given string and timestamp.
     * 
     * @param input
     *            The string to encode
     * 
     * @return A 52 character encoded version of the String representation
     */
    public static  String timeEncode(final String input) {
        return encodeWithSha256AndBase32(input + System.nanoTime());
    }


    /**
     * Encode a given string. Encodes the input with SHA 256 and Base32.
     *
     * @param input
     *            The string to encode
     * @return A 52 character encoded version of the String representation
     */
    public static String encodeWithSha256AndBase32(String input) {
        byte[] digest = null;
        try {
            final MessageDigest md = MessageDigest.getInstance("SHA-256");
            md.update(input.getBytes("UTF-8"));
            digest = md.digest();
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException ex) {
            throw new RuntimeException(ex);
        }

        final Base32 base32 = new Base32();
        //substring removes padding
        return base32.encodeAsString(digest).substring(0, 52);
    }
}