DATAREDIS-542 - Fix key expiration for RedisCache.putIfAbsent.

RedisCache now expires keys using putIfAbsent if the key was set. Previously, the key was only expired if the value was already present and the value matched the value stored inside of Redis.

Original Pull Request: #224

src/main/java/org/springframework/data/redis/cache/RedisCache.java

@@ -17,7 +17,6 @@
 package org.springframework.data.redis.cache;
 
 import static org.springframework.util.Assert.*;
-import static org.springframework.util.ObjectUtils.*;
 
 import java.lang.reflect.Constructor;
 import java.util.Arrays;
@@ -37,6 +36,7 @@ import org.springframework.data.redis.core.RedisOperations;
 import org.springframework.data.redis.serializer.RedisSerializer;
 import org.springframework.data.redis.serializer.StringRedisSerializer;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Cache implementation on top of Redis.
@@ -720,20 +720,27 @@ public class RedisCache implements Cache {
 		public byte[] doInRedis(BinaryRedisCacheElement element, RedisConnection connection) throws DataAccessException {
 
 			waitForLock(connection);
-			byte[] resultValue = put(element, connection);
 
-			if (nullSafeEquals(element.get(), resultValue)) {
+			byte existingValue[] = null;
+
+			boolean keyMaintenance;
+
+			byte[] keyBytes = element.getKeyBytes();
+			byte[] value = element.get();
+
+			if (connection.setNX(keyBytes, value)) {
+				keyMaintenance = true;
+			} else {
+				existingValue = connection.get(keyBytes);
+				keyMaintenance = ObjectUtils.nullSafeEquals(value, existingValue);
+			}
+
+			if (keyMaintenance) {
 				processKeyExpiration(element, connection);
 				maintainKnownKeys(element, connection);
 			}
 
-			return resultValue;
-		}
-
-		private byte[] put(BinaryRedisCacheElement element, RedisConnection connection) {
-
-			boolean valueWasSet = connection.setNX(element.getKeyBytes(), element.get());
-			return valueWasSet ? null : connection.get(element.getKeyBytes());
+			return existingValue;
 		}
 	}