Drop support for RxJava 1.

Closes #2469

src/main/java/org/springframework/data/repository/util/ReactiveWrapperConverters.java

@@ -22,8 +22,6 @@ import kotlinx.coroutines.flow.FlowKt;
 import kotlinx.coroutines.reactive.ReactiveFlowKt;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
-import rx.Observable;
-import rx.Single;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -54,8 +52,6 @@ import org.springframework.util.ClassUtils;
  * <p>
  * This class discovers reactive wrapper availability and their conversion support based on the class path. Reactive
  * wrapper types might be supported/on the class path but conversion may require additional dependencies.
- * <p>
- * <strong>Note:</strong> As of Spring Data 2.4, support for RxJava 1.x is deprecated in favor of RxJava 2 and 3.
  *
  * @author Mark Paluch
  * @author Oliver Gierke
@@ -72,12 +68,6 @@ public abstract class ReactiveWrapperConverters {
 
 	static {
 
-		if (ReactiveWrappers.isAvailable(ReactiveLibrary.RXJAVA1)) {
-
-			REACTIVE_WRAPPERS.add(RxJava1SingleWrapper.INSTANCE);
-			REACTIVE_WRAPPERS.add(RxJava1ObservableWrapper.INSTANCE);
-		}
-
 		if (ReactiveWrappers.isAvailable(ReactiveLibrary.RXJAVA2)) {
 
 			REACTIVE_WRAPPERS.add(RxJava2SingleWrapper.INSTANCE);
@@ -341,46 +331,6 @@ public abstract class ReactiveWrapperConverters {
 		}
 	}
 
-	// -------------------------------------------------------------------------
-	// RxJava 1 converters
-	// -------------------------------------------------------------------------
-
-	/**
-	 * Wrapper for RxJava 1's {@link Single}.
-	 */
-	private enum RxJava1SingleWrapper implements ReactiveTypeWrapper<Single<?>> {
-
-		INSTANCE;
-
-		@Override
-		public Class<? super Single<?>> getWrapperClass() {
-			return Single.class;
-		}
-
-		@Override
-		public Single<?> map(Object wrapper, Function<Object, Object> function) {
-			return ((Single<?>) wrapper).map(function::apply);
-		}
-	}
-
-	/**
-	 * Wrapper for RxJava 1's {@link Observable}.
-	 */
-	private enum RxJava1ObservableWrapper implements ReactiveTypeWrapper<Observable<?>> {
-
-		INSTANCE;
-
-		@Override
-		public Class<? super Observable<?>> getWrapperClass() {
-			return Observable.class;
-		}
-
-		@Override
-		public Observable<?> map(Object wrapper, Function<Object, Object> function) {
-			return ((Observable<?>) wrapper).map(function::apply);
-		}
-	}
-
 	// -------------------------------------------------------------------------
 	// RxJava 2 converters
 	// -------------------------------------------------------------------------

src/main/java/org/springframework/data/repository/util/ReactiveWrappers.java

@@ -35,8 +35,6 @@ import org.springframework.util.ClassUtils;
  * <p>
  * Supported types are discovered by their availability on the class path. This class is typically used to determine
  * multiplicity and whether a reactive wrapper type is acceptable for a specific operation.
- * <p>
- * <strong>Note:</strong> As of Spring Data 2.4, support for RxJava 1.x is deprecated in favor of RxJava 2 and 3.
  *
  * @author Mark Paluch
  * @author Christoph Strobl
@@ -45,9 +43,6 @@ import org.springframework.util.ClassUtils;
  * @author Hantsy Bai
  * @since 2.0
  * @see org.reactivestreams.Publisher
- * @see rx.Single
- * @see rx.Observable
- * @see rx.Completable
  * @see io.reactivex.Single
  * @see io.reactivex.Maybe
  * @see io.reactivex.Observable
@@ -68,12 +63,6 @@ public abstract class ReactiveWrappers {
 	private static final boolean PROJECT_REACTOR_PRESENT = ClassUtils.isPresent("reactor.core.publisher.Flux",
 			ReactiveWrappers.class.getClassLoader());
 
-	@Deprecated
-	private static final boolean RXJAVA1_PRESENT = ClassUtils.isPresent("rx.Observable",
-			ReactiveWrappers.class.getClassLoader())
-			&& ClassUtils.isPresent("rx.RxReactiveStreams",
-			ReactiveWrappers.class.getClassLoader());
-
 	@Deprecated
 	private static final boolean RXJAVA2_PRESENT = ClassUtils.isPresent("io.reactivex.Flowable",
 			ReactiveWrappers.class.getClassLoader());
@@ -98,17 +87,11 @@ public abstract class ReactiveWrappers {
 
 		PROJECT_REACTOR,
 
-		/**
-		 * @deprecated since 2.4, use RxJava 3 instead. To be removed with Spring Data 3.0.
-		 */
-		@Deprecated
-		RXJAVA1,
-
 		/**
 		 * @deprecated since 2.6, use RxJava 3 instead. To be removed with Spring Data 3.0.
 		 */
 		@Deprecated
-		RXJAVA2, RXJAVA3, KOTLIN_COROUTINES, MUTINY;
+		RXJAVA2, RXJAVA3, KOTLIN_COROUTINES;
 	}
 
 	/**
@@ -134,8 +117,6 @@ public abstract class ReactiveWrappers {
 		switch (reactiveLibrary) {
 			case PROJECT_REACTOR:
 				return PROJECT_REACTOR_PRESENT;
-			case RXJAVA1:
-				return RXJAVA1_PRESENT;
 			case RXJAVA2:
 				return RXJAVA2_PRESENT;
 			case RXJAVA3: