Add Predicates utility.

Original Pull Request: #2420

Author: mp911de

src/main/java/org/springframework/data/convert/CustomConversions.java

@@ -44,6 +44,7 @@
 import org.springframework.core.convert.support.GenericConversionService;
 import org.springframework.data.convert.ConverterBuilder.ConverterAware;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
+import org.springframework.data.util.Predicates;
 import org.springframework.data.util.Streamable;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -892,7 +893,7 @@ protected static class ConverterConfiguration {
 		 * @param userConverters must not be {@literal null} use {@link Collections#emptyList()} instead.
 		 */
 		public ConverterConfiguration(StoreConversions storeConversions, List<?> userConverters) {
-			this(storeConversions, userConverters, it -> true);
+			this(storeConversions, userConverters, Predicates.isTrue());
 		}
 
 		/**

src/main/java/org/springframework/data/spel/ExtensionAwareEvaluationContextProvider.java

@@ -38,6 +38,7 @@
 import org.springframework.data.spel.spi.Function;
 import org.springframework.data.util.Lazy;
 import org.springframework.data.util.Optionals;
+import org.springframework.data.util.Predicates;
 import org.springframework.expression.AccessException;
 import org.springframework.expression.EvaluationContext;
 import org.springframework.expression.MethodExecutor;
@@ -107,7 +108,7 @@ public ExtensionAwareEvaluationContextProvider(
 	 */
 	@Override
 	public StandardEvaluationContext getEvaluationContext(Object rootObject) {
-		return doGetEvaluationContext(rootObject, getExtensions(it -> true));
+		return doGetEvaluationContext(rootObject, getExtensions(Predicates.isTrue()));
 	}
 
 	/*

src/main/java/org/springframework/data/spel/ReactiveExtensionAwareEvaluationContextProvider.java

@@ -27,6 +27,7 @@
 import org.springframework.data.spel.spi.EvaluationContextExtension;
 import org.springframework.data.spel.spi.ExtensionIdAware;
 import org.springframework.data.spel.spi.ReactiveEvaluationContextExtension;
+import org.springframework.data.util.Predicates;
 import org.springframework.data.util.ReflectionUtils;
 import org.springframework.expression.EvaluationContext;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
@@ -93,7 +94,7 @@ public EvaluationContext getEvaluationContext(Object rootObject, ExpressionDepen
 	 */
 	@Override
 	public Mono<StandardEvaluationContext> getEvaluationContextLater(Object rootObject) {
-		return getExtensions(it -> true) //
+		return getExtensions(Predicates.isTrue()) //
 				.map(it -> evaluationContextProvider.doGetEvaluationContext(rootObject, it));
 	}
 

src/main/java/org/springframework/data/util/Predicates.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2021 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.util;
+
+import java.util.function.Predicate;
+
+import org.springframework.util.Assert;
+
+/**
+ * Utility methods to work with {@link Predicate}s.
+ *
+ * @author Mark Paluch
+ * @since 2.7
+ */
+public interface Predicates {
+
+	/**
+	 * A {@link Predicate} that yields always {@code true}.
+	 *
+	 * @return a {@link Predicate} that yields always {@code true}.
+	 */
+	static <T> Predicate<T> isTrue() {
+		return t -> true;
+	}
+
+	/**
+	 * A {@link Predicate} that yields always {@code false}.
+	 *
+	 * @return a {@link Predicate} that yields always {@code false}.
+	 */
+	static <T> Predicate<T> isFalse() {
+		return t -> false;
+	}
+
+	/**
+	 * Returns a {@link Predicate} that represents the logical negation of {@code predicate}.
+	 *
+	 * @return a {@link Predicate} that represents the logical negation of {@code predicate}.
+	 */
+	static <T> Predicate<T> negate(Predicate<T> predicate) {
+
+		Assert.notNull(predicate, "Predicate must not be null!");
+		return predicate.negate();
+	}
+}