Add adapters for Java functional interfaces

Resolves #4672

Author: fmbenhassine

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/function/ConsumerItemWriter.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2024 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.batch.item.function;
+
+import java.util.function.Consumer;
+
+import org.springframework.batch.item.Chunk;
+import org.springframework.batch.item.ItemWriter;
+import org.springframework.util.Assert;
+
+/**
+ * Adapter for a {@link Consumer} to an {@link ItemWriter}.
+ *
+ * @param <T> type of items to write
+ * @author Mahmoud Ben Hassine
+ * @since 5.2
+ */
+public class ConsumerItemWriter<T> implements ItemWriter<T> {
+
+	private final Consumer<T> consumer;
+
+	/**
+	 * Create a new {@link ConsumerItemWriter}.
+	 * @param consumer the consumer to use to write items. Must not be {@code null}.
+	 */
+	public ConsumerItemWriter(Consumer<T> consumer) {
+		Assert.notNull(consumer, "A consumer is required");
+		this.consumer = consumer;
+	}
+
+	@Override
+	public void write(Chunk<? extends T> items) throws Exception {
+		items.forEach(this.consumer);
+	}
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/function/PredicateFilteringItemProcessor.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2024 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.batch.item.function;
+
+import java.util.function.Predicate;
+
+import org.springframework.batch.item.ItemProcessor;
+import org.springframework.util.Assert;
+
+/**
+ * A filtering {@link ItemProcessor} that is based on a {@link Predicate}. Items for which
+ * the predicate returns {@code true} will be filtered.
+ *
+ * @param <T> type of item to process
+ * @author Mahmoud Ben Hassine
+ * @since 5.2
+ */
+public class PredicateFilteringItemProcessor<T> implements ItemProcessor<T, T> {
+
+	private final Predicate<T> predicate;
+
+	/**
+	 * Create a new {@link PredicateFilteringItemProcessor}.
+	 * @param predicate the predicate to use to filter items. Must not be {@code null}.
+	 */
+	public PredicateFilteringItemProcessor(Predicate<T> predicate) {
+		Assert.notNull(predicate, "A predicate is required");
+		this.predicate = predicate;
+	}
+
+	@Override
+	public T process(T item) throws Exception {
+		return this.predicate.test(item) ? null : item;
+	}
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/function/SupplierItemReader.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2024 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.batch.item.function;
+
+import java.util.function.Supplier;
+
+import org.springframework.batch.item.ItemReader;
+import org.springframework.util.Assert;
+
+/**
+ * Adapter for a {@link Supplier} to an {@link ItemReader}.
+ *
+ * @param <T> type of items to read
+ * @author Mahmoud Ben Hassine
+ * @since 5.2
+ */
+public class SupplierItemReader<T> implements ItemReader<T> {
+
+	private final Supplier<T> supplier;
+
+	/**
+	 * Create a new {@link SupplierItemReader}.
+	 * @param supplier the supplier to use to read items. Must not be {@code null}.
+	 */
+	public SupplierItemReader(Supplier<T> supplier) {
+		Assert.notNull(supplier, "A supplier is required");
+		this.supplier = supplier;
+	}
+
+	@Override
+	public T read() throws Exception {
+		return this.supplier.get();
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/function/ConsumerItemWriterTests.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2024 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.batch.item.function;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.batch.item.Chunk;
+
+/**
+ * Test class for {@link ConsumerItemWriter}.
+ *
+ * @author Mahmoud Ben Hassine
+ */
+class ConsumerItemWriterTests {
+
+	private final List<String> items = new ArrayList<>();
+
+	private final Consumer<String> consumer = items::add;
+
+	@Test
+	void testMandatoryConsumer() {
+		Assertions.assertThrows(IllegalArgumentException.class, () -> new ConsumerItemWriter<String>(null),
+				"A consumer is required");
+	}
+
+	@Test
+	void testWrite() throws Exception {
+		// given
+		Chunk<String> chunk = Chunk.of("foo", "bar");
+		ConsumerItemWriter<String> consumerItemWriter = new ConsumerItemWriter<>(this.consumer);
+
+		// when
+		consumerItemWriter.write(chunk);
+
+		// then
+		Assertions.assertIterableEquals(chunk, this.items);
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/function/PredicateFilteringItemProcessorTests.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2024 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.batch.item.function;
+
+import java.util.function.Predicate;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test class for {@link PredicateFilteringItemProcessor}.
+ *
+ * @author Mahmoud Ben Hassine
+ */
+class PredicateFilteringItemProcessorTests {
+
+	private final Predicate<String> foos = item -> item.startsWith("foo");
+
+	@Test
+	void testMandatoryPredicate() {
+		Assertions.assertThrows(IllegalArgumentException.class, () -> new PredicateFilteringItemProcessor<String>(null),
+				"A predicate is required");
+	}
+
+	@Test
+	void testProcess() throws Exception {
+		// given
+		PredicateFilteringItemProcessor<String> processor = new PredicateFilteringItemProcessor<>(this.foos);
+
+		// when & then
+		Assertions.assertNull(processor.process("foo1"));
+		Assertions.assertNull(processor.process("foo2"));
+		Assertions.assertEquals("bar", processor.process("bar"));
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/function/SupplierItemReaderTests.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2024 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.batch.item.function;
+
+import java.util.function.Supplier;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test class for {@link SupplierItemReader}.
+ *
+ * @author Mahmoud Ben Hassine
+ */
+class SupplierItemReaderTests {
+
+	private final Supplier<String> supplier = new Supplier<>() {
+		private int count = 1;
+
+		@Override
+		public String get() {
+			return count <= 2 ? "foo" + count++ : null;
+		}
+	};
+
+	@Test
+	void testMandatorySupplier() {
+		Assertions.assertThrows(IllegalArgumentException.class, () -> new SupplierItemReader<String>(null),
+				"A supplier is required");
+	}
+
+	@Test
+	void testRead() throws Exception {
+		// given
+		SupplierItemReader<String> supplierItemReader = new SupplierItemReader<>(supplier);
+
+		// when & then
+		Assertions.assertEquals("foo1", supplierItemReader.read());
+		Assertions.assertEquals("foo2", supplierItemReader.read());
+		Assertions.assertNull(supplierItemReader.read());
+	}
+
+}