Extract IdGenerator into a top-level class

spring-messaging/src/main/java/org/springframework/messaging/MessageHeaders.java

@@ -20,8 +20,6 @@ import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
-import java.math.BigInteger;
-import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -30,12 +28,13 @@ import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Random;
 import java.util.Set;
 import java.util.UUID;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.springframework.util.AlternativeJdkIdGenerator;
+import org.springframework.util.IdGenerator;
 
 /**
  * The headers for a {@link Message}
@@ -243,40 +242,4 @@ public final class MessageHeaders implements Map<String, Object>, Serializable {
 		in.defaultReadObject();
 	}
 
-	public static interface IdGenerator {
-		UUID generateId();
-	}
-
-	/**
-	 * A variation of {@link UUID#randomUUID()} that uses {@link SecureRandom} only for
-	 * the initial seed and {@link Random} thereafter, which provides better performance
-	 * in exchange for less securely random id's.
-	 */
-	public static class AlternativeJdkIdGenerator implements IdGenerator {
-
-		private final Random random;
-
-		public AlternativeJdkIdGenerator() {
-			byte[] seed = new SecureRandom().generateSeed(8);
-			this.random = new Random(new BigInteger(seed).longValue());
-		}
-
-		public UUID generateId() {
-
-			byte[] randomBytes = new byte[16];
-			this.random.nextBytes(randomBytes);
-
-			long mostSigBits = 0;
-			for (int i = 0; i < 8; i++) {
-				mostSigBits = (mostSigBits << 8) | (randomBytes[i] & 0xff);
-			}
-			long leastSigBits = 0;
-			for (int i = 8; i < 16; i++) {
-				leastSigBits = (leastSigBits << 8) | (randomBytes[i] & 0xff);
-			}
-
-			return new UUID(mostSigBits, leastSigBits);
-		}
-	}
-
 }