org.molgenis.data.populate.IdGeneratorImpl Maven / Gradle / Ivy
package org.molgenis.data.populate;
import static org.molgenis.data.populate.IdGenerator.Strategy.SEQUENTIAL_UUID;
import com.google.common.io.BaseEncoding;
import java.security.SecureRandom;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;
import org.molgenis.data.util.UniqueId;
import org.springframework.stereotype.Component;
/** Generates identifiers. */
@Component
public class IdGeneratorImpl implements IdGenerator {
private static final BaseEncoding BASE_ENCODING = BaseEncoding.base32().omitPadding().lowerCase();
private static class Holder {
static final SecureRandom SECURE_RANDOM = new SecureRandom();
static final UniqueId UNIQUE_ID = new UniqueId();
}
@Override
public String generateId() {
return generateId(SEQUENTIAL_UUID);
}
@Override
public String generateId(Strategy strategy) {
byte[] bytes = generateBytes(strategy);
return BASE_ENCODING.encode(bytes);
}
private byte[] generateBytes(Strategy strategy) {
switch (strategy) {
case SECURE_RANDOM:
return generateRandomBytes(16, Holder.SECURE_RANDOM);
case LONG_SECURE_RANDOM:
return generateRandomBytes(20, Holder.SECURE_RANDOM);
case SHORT_SECURE_RANDOM:
return generateRandomBytes(5, Holder.SECURE_RANDOM);
case SHORT_RANDOM:
return generateRandomBytes(5, ThreadLocalRandom.current());
case SEQUENTIAL_UUID:
default:
return Holder.UNIQUE_ID.getId();
}
}
/**
* Generates a number of random bytes.
*
* The chance of collisions of k IDs taken from a population of N possibilities is
* 1 - Math.exp(-0.5 * k * (k - 1) / N)
*
*
A couple collision chances for 5 bytes N = 256^5:
*
*
* 1 0.0 10 4.092726157978177e-11 100 4.501998773775995e-09 1000 4.5429250039585867e-07 10000 4.546915386183237e-05 100000 0.004537104138253034 1000000 0.36539143049797307
*
* @see Hash collision
* probabilities
*/
private byte[] generateRandomBytes(int nBytes, Random random) {
byte[] randomBytes = new byte[nBytes];
random.nextBytes(randomBytes);
return randomBytes;
}
}