Add Nullable annotation to parameter of overridden equals method.

Closes: #2450
Original pull request: #2451

Author: christophstrobl

src/main/asciidoc/observability/_conventions.adoc

@@ -0,0 +1,6 @@
+[[observability-conventions]]
+=== Observability - Conventions
+
+Below you can find a list of all `GlobalObservabilityConventions` and `ObservabilityConventions` declared by this project.
+
+

src/main/asciidoc/observability/_metrics.adoc

@@ -0,0 +1,42 @@
+[[observability-metrics]]
+=== Observability - Metrics
+
+Below you can find a list of all metrics declared by this project.
+
+[[observability-metrics-redis-command-observation]]
+==== Redis Command Observation
+
+____
+Timer created around a Redis command execution.
+____
+
+**Metric name** `spring.data.redis`. **Type** `timer` and **base unit** `seconds`.
+
+Fully qualified name of the enclosing class `org.springframework.data.redis.connection.lettuce.observability.RedisObservation`.
+
+
+
+.Low cardinality Keys
+[cols="a,a"]
+|===
+|Name | Description
+|`db.operation`|Redis command value.
+|`db.redis.database_index`|Redis database index.
+|`db.system`|Database system.
+|`db.user`|Redis user.
+|`net.peer.name`|Name of the database host.
+|`net.peer.port`|Logical remote port number.
+|`net.sock.peer.addr`|Mongo peer address.
+|`net.sock.peer.port`|Mongo peer port.
+|`net.transport`|Network transport.
+|===
+
+.High cardinality Keys
+[cols="a,a"]
+|===
+|Name | Description
+|`db.statement`|Redis statement.
+|`spring.data.redis.command.error`|Redis error response.
+|===
+
+

src/main/asciidoc/observability/_spans.adoc

@@ -0,0 +1,35 @@
+[[observability-spans]]
+=== Observability - Spans
+
+Below you can find a list of all spans declared by this project.
+
+[[observability-spans-redis-command-observation]]
+==== Redis Command Observation Span
+
+> Timer created around a Redis command execution.
+
+**Span name** `spring.data.redis`.
+
+Fully qualified name of the enclosing class `org.springframework.data.redis.connection.lettuce.observability.RedisObservation`.
+
+
+
+.Tag Keys
+|===
+|Name | Description
+|`db.operation`|Redis command value.
+|`db.redis.database_index`|Redis database index.
+|`db.statement`|Redis statement.
+|`db.system`|Database system.
+|`db.user`|Redis user.
+|`net.peer.name`|Name of the database host.
+|`net.peer.port`|Logical remote port number.
+|`net.sock.peer.addr`|Mongo peer address.
+|`net.sock.peer.port`|Mongo peer port.
+|`net.transport`|Network transport.
+|`spring.data.redis.command.error`|Redis error response.
+|===
+
+
+
+

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

@@ -18,6 +18,7 @@
 import java.time.Instant;
 import java.util.concurrent.TimeUnit;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -184,7 +185,7 @@ public Instant getLastReset() {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;

src/main/java/org/springframework/data/redis/connection/BitFieldSubCommands.java

@@ -155,7 +155,7 @@ public Iterator<BitFieldSubCommand> iterator() {
 	 * @see java.lang.Object#equals(java.lang.Object)
 	 */
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o) {
 			return true;
 		}
@@ -456,7 +456,7 @@ public String toString() {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;
@@ -576,7 +576,7 @@ public String asString() {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;
@@ -644,7 +644,7 @@ public Offset getOffset() {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;
@@ -744,7 +744,7 @@ public long getValue() {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o) {
 				return true;
 			}
@@ -915,7 +915,7 @@ public enum Overflow {
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;

src/main/java/org/springframework/data/redis/connection/ClusterCommandExecutor.java

@@ -682,7 +682,7 @@ public int getPosition() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o)
 				return true;
 			if (o == null || getClass() != o.getClass())

src/main/java/org/springframework/data/redis/connection/DefaultStringTuple.java

@@ -19,6 +19,7 @@
 
 import org.springframework.data.redis.connection.RedisZSetCommands.Tuple;
 import org.springframework.data.redis.connection.StringRedisConnection.StringTuple;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -77,7 +78,7 @@ public String toString() {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 		if (this == o)
 			return true;
 		if (o == null || getClass() != o.getClass())

src/main/java/org/springframework/data/redis/connection/DefaultTuple.java

@@ -19,6 +19,8 @@
 
 import org.springframework.data.redis.connection.RedisZSetCommands.Tuple;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Default implementation for {@link Tuple} interface.
  *
@@ -58,7 +60,7 @@ public byte[] getValue() {
 		return value;
 	}
 
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 		if (this == obj)
 			return true;
 		if (obj == null)

src/main/java/org/springframework/data/redis/connection/ReactiveRedisConnection.java

@@ -374,7 +374,7 @@ public O getOutput() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o)
 				return true;
 			if (o == null || getClass() != o.getClass())

src/main/java/org/springframework/data/redis/connection/ReactiveSubscription.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.redis.connection;
 
+import org.springframework.lang.Nullable;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -194,7 +195,7 @@ public M getMessage() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o)
 				return true;
 			if (o == null || getClass() != o.getClass())
@@ -260,7 +261,7 @@ public P getPattern() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o)
 				return true;
 			if (o == null || getClass() != o.getClass())