Add a composite for TaskDecorator

See gh-23692

spring-core/src/main/java/org/springframework/core/task/CompositeTaskDecorator.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2002-2019 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.core.task;
+
+import org.springframework.util.Assert;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * Composite {@link TaskDecorator} that delegates to other task decorators.
+ *
+ * @author Tadaya Tsuyukubo
+ * @since 5.2
+ */
+public class CompositeTaskDecorator implements TaskDecorator {
+
+	private final List<TaskDecorator> taskDecorators = new ArrayList<>();
+
+	/**
+	 * Create a new {@link CompositeTaskDecorator}.
+	 *
+	 * @param taskDecorators the taskDecorators to delegate to
+	 * @throws IllegalArgumentException if {@code taskDecorators} is {@code null}
+	 */
+	public CompositeTaskDecorator(Collection<? extends TaskDecorator> taskDecorators) {
+		Assert.notNull(taskDecorators, "taskDecorators must not be null");
+		this.taskDecorators.addAll(taskDecorators);
+	}
+
+	/**
+	 * Create a new {@link CompositeTaskDecorator}.
+	 *
+	 * @param taskDecorators the taskDecorators to delegate to
+	 * @throws IllegalArgumentException if {@code taskDecorators} is {@code null}
+	 */
+	public CompositeTaskDecorator(TaskDecorator... taskDecorators) {
+		Assert.notNull(taskDecorators, "taskDecorators must not be null");
+		this.taskDecorators.addAll(Arrays.asList(taskDecorators));
+	}
+
+	/**
+	 * Add a delegating {@link TaskDecorator}.
+	 *
+	 * @param taskDecorator a taskDecorator to delegate to
+	 * @return {@code true} when the taskDecorator is successfully added
+	 * @throws IllegalArgumentException if {@code taskDecorator} is {@code null}
+	 */
+	public boolean add(TaskDecorator taskDecorator) {
+		Assert.notNull(taskDecorator, "taskDecorator must not be null");
+		return this.taskDecorators.add(taskDecorator);
+	}
+
+	@Override
+	public Runnable decorate(Runnable runnable) {
+		Assert.notNull(runnable, "runnable must not be null");
+
+		for (TaskDecorator taskDecorator : this.taskDecorators) {
+			runnable = taskDecorator.decorate(runnable);
+		}
+		return runnable;
+	}
+
+}

spring-core/src/test/java/org/springframework/core/task/CompositeTaskDecoratorTests.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2002-2019 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.core.task;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Test for {@link CompositeTaskDecorator}.
+ *
+ * @author Tadaya Tsuyukubo
+ */
+class CompositeTaskDecoratorTests {
+
+	@Test
+	void decorate() {
+		List<String> decorated = new ArrayList<>();
+		CompositeTaskDecorator compositeTaskDecorator = new CompositeTaskDecorator(runnable -> {
+			decorated.add("foo");
+			return runnable;
+		});
+		compositeTaskDecorator.add(runnable -> {
+			decorated.add("bar");
+			return runnable;
+		});
+
+		Runnable runnable = compositeTaskDecorator.decorate(() -> {
+			decorated.add("baz");
+		});
+
+		runnable.run();
+
+		assertThat(decorated).containsExactly("foo", "bar", "baz");
+	}
+}