Added MD5 hashing utils.

org.springframework.core/src/main/java/org/springframework/util/Md5HashUtils.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2008 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.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/**
+ * Miscellaneous method for calculating MD5 hashes.
+ *
+ * @author Arjen Poutsma
+ * @since 3.0
+ */
+public abstract class Md5HashUtils {
+
+	private static final char[] HEX_CHARS =
+			{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',};
+
+	/**
+	 * Calculates the MD5 hash of the given bytes.
+	 *
+	 * @param bytes the bytes to calculate the hash over
+	 * @return the hash
+	 */
+	public static byte[] getHash(byte[] bytes) {
+		try {
+			// MessageDigest is not thread-safe
+			MessageDigest messageDigest = MessageDigest.getInstance("MD5");
+			return messageDigest.digest(bytes);
+		}
+		catch (NoSuchAlgorithmException ex) {
+			throw new IllegalStateException("Could not find MD5 MessageDigest instance", ex);
+		}
+	}
+
+	private static char[] getHashChars(byte[] bytes) {
+		byte[] hash = getHash(bytes);
+		char chars[] = new char[32];
+		for (int i = 0; i < chars.length; i = i + 2) {
+			byte b = hash[i / 2];
+			chars[i] = HEX_CHARS[(b >>> 0x4) & 0xf];
+			chars[i + 1] = HEX_CHARS[b & 0xf];
+		}
+		return chars;
+	}
+
+	/**
+	 * Returns a hex string representation of the MD5 hash of the given bytes.
+	 *
+	 * @param bytes the bytes to calculate the hash over
+	 * @return a hexadecimal hash string
+	 */
+	public static String getHashString(byte[] bytes) {
+		return new String(getHashChars(bytes));
+	}
+
+	/**
+	 * Appends a hex string representation of the MD5 hash of the given bytes to the given {@link StringBuilder}.
+	 *
+	 * @param bytes   the bytes to calculate the hash over
+	 * @param builder the string builder to append the hash to
+	 * @return the given string builder
+	 */
+	public static StringBuilder appendHashString(byte[] bytes, StringBuilder builder) {
+		builder.append(getHashChars(bytes));
+		return builder;
+	}
+
+}