Implement codec adapter #1122

- Supports using different codecs for keys and values

Original pull request: #1123.

src/main/java/io/lettuce/core/codec/RedisCodecAdapter.java

@@ -0,0 +1,71 @@
+package io.lettuce.core.codec;
+
+import java.nio.ByteBuffer;
+
+/*
+ * Copyright 2011-2019 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.
+ */
+/**
+ * A {@link RedisCodecAdapter} combines different codecs to encode/decode key and value
+ * to the command output.
+ * 
+ * @author Dimitris Mandalidis
+ */
+public final class RedisCodecAdapter {
+
+    private RedisCodecAdapter() {}
+
+    /**
+     * Returns new {@link RedisCodec}
+     * @param <K> the type of the key
+     * @param <V> the type of the value
+     * @param keyCodec the codec to encode/decode the keys
+     * @param valueCodec the codec to encode/decode the values
+     * @return
+     */
+    public static <K, V> RedisCodec<K, V> of(RedisCodec<K, ?> keyCodec, RedisCodec<?, V> valueCodec) {
+        return new RedisCodecWrapper<K, V>(keyCodec, valueCodec);
+    }
+
+    private static class RedisCodecWrapper<K, V> implements RedisCodec<K, V> {
+        private final RedisCodec<K, ?> keyCodec;
+        private final RedisCodec<?, V> valueCodec;
+
+        RedisCodecWrapper(RedisCodec<K, ?> keyCodec, RedisCodec<?, V> valueCodec) {
+            this.keyCodec = keyCodec;
+            this.valueCodec = valueCodec;
+        }
+
+        @Override
+        public K decodeKey(ByteBuffer bytes) {
+            return keyCodec.decodeKey(bytes);
+        }
+
+        @Override
+        public V decodeValue(ByteBuffer bytes) {
+            return valueCodec.decodeValue(bytes);
+        }
+
+        @Override
+        public ByteBuffer encodeKey(K key) {
+            return keyCodec.encodeKey(key);
+        }
+
+        @Override
+        public ByteBuffer encodeValue(V value) {
+            return valueCodec.encodeValue(value);
+        }
+    }
+}