copy .util

Author: XDean

pom.xml

@@ -23,6 +23,11 @@
 			<version>4.12</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>com.google.code.findbugs</groupId>
+			<artifactId>jsr305</artifactId>
+			<version>3.0.1</version>
+		</dependency>
 	</dependencies>
 
 	<developers>

src/main/java/org/springframework/util/AlternativeJdkIdGenerator.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2002-2015 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;
+
+/**
+ * An {@link IdGenerator} that uses {@link SecureRandom} for the initial seed and
+ * {@link Random} thereafter, instead of calling {@link UUID#randomUUID()} every
+ * time as {@link org.springframework.util.JdkIdGenerator JdkIdGenerator} does.
+ * This provides a better balance between securely random ids and performance.
+ *
+ * @author Rossen Stoyanchev
+ * @author Rob Winch
+ * @since 4.0
+ */
+public class AlternativeJdkIdGenerator implements IdGenerator {
+
+	private final Random random;
+
+
+	public AlternativeJdkIdGenerator() {
+		SecureRandom secureRandom = new SecureRandom();
+		byte[] seed = new byte[8];
+		secureRandom.nextBytes(seed);
+		this.random = new Random(new BigInteger(seed).longValue());
+	}
+
+
+	@Override
+	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);
+	}
+
+}