Extract IdGenerator into a top-level class

spring-core/src/main/java/org/springframework/util/AlternativeJdkIdGenerator.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2002-2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.util;
+
+import java.math.BigInteger;
+import java.security.SecureRandom;
+import java.util.Random;
+import java.util.UUID;
+
+/**
+ * A variation of {@link UUID#randomUUID()} that uses {@link SecureRandom} only for
+ * the initial seed and {@link Random} thereafter. This provides better performance
+ * in exchange for less securely random id's.
+ *
+ * @author Rossen Stoyanchev
+ * @author Rob Winch
+ * @since 4.0
+ */
+public 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);
+	}
+
+}

spring-core/src/main/java/org/springframework/util/IdGenerator.java

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+/*
+ * Copyright 2002-2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.util;
+
+import java.util.UUID;
+
+/**
+ * Contract for generating {@link UUID} identifiers.
+ *
+ * @author Rossen Stoyanchev
+ * @since 4.0
+ */
+public interface IdGenerator {
+
+	/**
+	 * Generate a new identifier.
+	 * @return the generated identifier
+	 */
+	UUID generateId();
+
+}