Add Nullable annotation to parameter of overridden equals method.

Closes #1374
Original pull request #1375

Author: christophstrobl

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/Identifier.java

@@ -208,7 +208,7 @@ public Class<?> getTargetType() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o)
 				return true;
@@ -272,7 +272,7 @@ public V get(Object key) {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) return true;
 		if (o == null || getClass() != o.getClass()) return false;

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/InsertSubject.java

@@ -17,6 +17,8 @@
 
 import java.util.Objects;
 
+import org.springframework.lang.Nullable;
+
 /**
  * The subject of an insert, described by the entity instance and its {@link Identifier}, where identifier contains
  * information about data that needs to be considered for the insert but which is not part of the entity. Namely
@@ -50,7 +52,7 @@ public Identifier getIdentifier() {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o)
 			return true;

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/SqlGenerator.java

@@ -1001,7 +1001,7 @@ Column getParentId() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o) {
 				return true;

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/mapping/AggregateReference.java

@@ -65,7 +65,7 @@ public ID getId() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o)
 				return true;

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/mapping/JdbcValue.java

@@ -55,7 +55,7 @@ public SQLType getJdbcType() {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o)
 			return true;

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/repository/query/JdbcQueryCreator.java

@@ -352,7 +352,7 @@ static private final class Join {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 
 			if (this == o)
 				return true;

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/core/NamedParameterUtils.java

@@ -382,7 +382,7 @@ int getEndIndex() {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o)
 				return true;
 			if (!(o instanceof ParameterHolder))

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/mapping/OutboundRow.java

@@ -24,6 +24,7 @@
 import java.util.function.BiConsumer;
 
 import org.springframework.data.relational.core.sql.SqlIdentifier;
+import org.springframework.lang.Nullable;
 import org.springframework.r2dbc.core.Parameter;
 import org.springframework.util.Assert;
 
@@ -195,7 +196,7 @@ public Set<Entry<SqlIdentifier, Parameter>> entrySet() {
 	}
 
 	@Override
-	public boolean equals(final Object o) {
+	public boolean equals(@Nullable final Object o) {
 
 		if (this == o) {
 			return true;

spring-data-r2dbc/src/test/java/org/springframework/data/r2dbc/repository/AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -142,7 +142,7 @@ public static class LegoSet {
 		}
 
 		@Override
-		public boolean equals(Object o) {
+		public boolean equals(@Nullable Object o) {
 			if (this == o)
 				return true;
 			if (o == null || getClass() != o.getClass())

spring-data-relational/src/main/java/org/springframework/data/relational/core/mapping/DerivedSqlIdentifier.java

@@ -21,6 +21,7 @@
 
 import org.springframework.data.relational.core.sql.IdentifierProcessing;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -69,7 +70,7 @@ public String getReference(IdentifierProcessing processing) {
 	}
 
 	@Override
-	public boolean equals(Object o) {
+	public boolean equals(@Nullable Object o) {
 
 		if (this == o) {
 			return true;