Simplify logic in RedisMessageListenerContainer and supporting classes.

Closes #2662
Original pull request: #2663

Author: jxblum

src/main/java/org/springframework/data/redis/listener/AbstractTopic.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2017-2023 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
+ *
+ *      https://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.data.redis.listener;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * Abstract base class for defining {@link Topic Topics}.
+ *
+ * @author John Blum
+ * @see org.springframework.data.redis.listener.Topic
+ * @since 3.2.0
+ */
+abstract class AbstractTopic implements Topic {
+
+	private final String name;
+
+	AbstractTopic(String label, String name) {
+		Assert.notNull(name,() -> label + " must not be null");
+		this.name = name;
+	}
+
+	@Override
+	public String getTopic() {
+		return this.name;
+	}
+
+	@Override
+	public boolean equals(@Nullable Object obj) {
+
+		if (this == obj) {
+			return true;
+		}
+
+		if (!(obj instanceof AbstractTopic that)) {
+			return false;
+		}
+
+		// Must be exact Topic type
+		if (this.getClass() != that.getClass()) {
+			return false;
+		}
+
+		return ObjectUtils.nullSafeEquals(this.getTopic(), that.getTopic());
+	}
+
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHashCode(getTopic());
+	}
+
+	@Override
+	public String toString() {
+		return getTopic();
+	}
+}

src/main/java/org/springframework/data/redis/listener/ChannelTopic.java

@@ -15,71 +15,32 @@
  */
 package org.springframework.data.redis.listener;
 
-import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
-import org.springframework.util.ObjectUtils;
-
 /**
- * Channel topic implementation (maps to a Redis channel).
+ * {@link Topic Channel Topic} implementation mapping to a Redis channel.
  *
  * @author Costin Leau
  * @author Mark Paluch
+ * @author John Blum
  */
-public class ChannelTopic implements Topic {
-
-	private final String channelName;
-
-	/**
-	 * Constructs a new {@link ChannelTopic} instance.
-	 *
-	 * @param name must not be {@literal null}.
-	 */
-	public ChannelTopic(String name) {
-
-		Assert.notNull(name, "Topic name must not be null");
-
-		this.channelName = name;
-	}
+public class ChannelTopic extends AbstractTopic {
 
 	/**
 	 * Create a new {@link ChannelTopic} for channel subscriptions.
 	 *
-	 * @param name the channel name, must not be {@literal null} or empty.
-	 * @return the {@link ChannelTopic} for {@code channelName}.
+	 * @param channelName {@link String name} of the Redis channel; must not be {@literal null} or {@literal empty}.
+	 * @return the {@link ChannelTopic} for the given {@code channelName}.
 	 * @since 2.1
 	 */
-	public static ChannelTopic of(String name) {
-		return new ChannelTopic(name);
+	public static ChannelTopic of(String channelName) {
+		return new ChannelTopic(channelName);
 	}
 
 	/**
-	 * @return topic name.
+	 * Constructs a new {@link ChannelTopic} instance.
+	 *
+	 * @param channelName must not be {@literal null}.
 	 */
-	@Override
-	public String getTopic() {
-		return channelName;
-	}
-
-	@Override
-	public String toString() {
-		return channelName;
-	}
-
-	@Override
-	public boolean equals(@Nullable Object o) {
-
-		if (this == o)
-			return true;
-		if (o == null || getClass() != o.getClass())
-			return false;
-
-		ChannelTopic that = (ChannelTopic) o;
-
-		return ObjectUtils.nullSafeEquals(channelName, that.channelName);
-	}
-
-	@Override
-	public int hashCode() {
-		return ObjectUtils.nullSafeHashCode(channelName);
+	public ChannelTopic(String channelName) {
+		super("Topic name", channelName);
 	}
 }

src/main/java/org/springframework/data/redis/listener/PatternTopic.java

@@ -15,72 +15,32 @@
  */
 package org.springframework.data.redis.listener;
 
-import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
-import org.springframework.util.ObjectUtils;
-
 /**
- * Pattern topic (matching multiple channels).
+ * {@link Topic} {@link String pattern} matching multiple Redis channels.
  *
  * @author Costin Leau
  * @author Mark Paluch
  * @author Christoph Strobl
  */
-public class PatternTopic implements Topic {
-
-	private final String channelPattern;
-
-	/**
-	 * Constructs a new {@link PatternTopic} instance.
-	 *
-	 * @param pattern must not be {@literal null}.
-	 */
-	public PatternTopic(String pattern) {
-
-		Assert.notNull(pattern, "Pattern must not be null");
-
-		this.channelPattern = pattern;
-	}
+public class PatternTopic extends AbstractTopic {
 
 	/**
 	 * Create a new {@link PatternTopic} for channel subscriptions based on a {@code pattern}.
 	 *
-	 * @param pattern the channel pattern, must not be {@literal null} or empty.
-	 * @return the {@link PatternTopic} for {@code pattern}.
+	 * @param pattern {@link String pattern} used to match channels; must not be {@literal null} or {@literal empty}.
+	 * @return the {@link PatternTopic} for the given {@code pattern}.
 	 * @since 2.1
 	 */
 	public static PatternTopic of(String pattern) {
 		return new PatternTopic(pattern);
 	}
 
 	/**
-	 * @return channel pattern.
+	 * Constructs a new {@link PatternTopic} instance.
+	 *
+	 * @param channelPattern must not be {@literal null}.
 	 */
-	@Override
-	public String getTopic() {
-		return channelPattern;
-	}
-
-	@Override
-	public String toString() {
-		return channelPattern;
-	}
-
-	@Override
-	public boolean equals(@Nullable Object o) {
-
-		if (this == o)
-			return true;
-		if (o == null || getClass() != o.getClass())
-			return false;
-
-		PatternTopic that = (PatternTopic) o;
-
-		return ObjectUtils.nullSafeEquals(channelPattern, that.channelPattern);
-	}
-
-	@Override
-	public int hashCode() {
-		return ObjectUtils.nullSafeHashCode(channelPattern);
+	public PatternTopic(String channelPattern) {
+		super("Pattern", channelPattern);
 	}
 }