Added Builder for ClassifierCompositeItemProcessor

resolves #BATCH-2618

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/support/ClassifierCompositeItemProcessor.java

@@ -36,7 +36,8 @@ public class ClassifierCompositeItemProcessor<I,O> implements ItemProcessor<I, O
 			new ClassifierSupport<I, ItemProcessor<?, ? extends O>> (null);
 
 	/**
-	 * @param classifier the classifier to set
+	 * Establishes the classifier that will determine which {@link ItemProcessor} to use.
+	 * @param classifier the {@link Classifier} to set
 	 */
 	public void setClassifier(Classifier<? super I, ItemProcessor<?, ? extends O>> classifier) {
 		this.classifier = classifier;

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/support/builder/ClassifierCompositeItemProcessorBuilder.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017 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
+ *
+ *          http://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.support.builder;
+
+import org.springframework.batch.item.ItemProcessor;
+import org.springframework.batch.item.support.ClassifierCompositeItemProcessor;
+import org.springframework.classify.Classifier;
+import org.springframework.util.Assert;
+
+/**
+ * Creates a fully qualified {@link ClassifierCompositeItemProcessor}.
+ *
+ * @author Glenn Renfro
+ *
+ * @since 4.0
+ */
+public class ClassifierCompositeItemProcessorBuilder<I, O> {
+
+	private Classifier<? super I, ItemProcessor<?, ? extends O>> classifier;
+
+	/**
+	 * Establishes the classifier that will determine which {@link ItemProcessor} to use.
+	 * @param classifier the classifier to set
+	 * @return this instance for method chaining
+	 * @see ClassifierCompositeItemProcessor#setClassifier(Classifier)
+	 */
+	public ClassifierCompositeItemProcessorBuilder<I, O> classifier(Classifier<? super I, ItemProcessor<?, ? extends O>> classifier) {
+		this.classifier = classifier;
+
+		return this;
+	}
+
+	/**
+	 * Returns a fully constructed {@link ClassifierCompositeItemProcessor}.
+	 *
+	 * @return a new {@link ClassifierCompositeItemProcessor}
+	 */
+	public ClassifierCompositeItemProcessor<I, O> build() {
+		Assert.notNull(classifier, "A classifier is required.");
+
+		ClassifierCompositeItemProcessor<I, O> processor = new ClassifierCompositeItemProcessor<>();
+		processor.setClassifier(this.classifier);
+		return processor;
+	}
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/support/builder/ClassifierCompositeItemProcessorBuilderTests.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2017 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
+ *
+ *          http://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.support.builder;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Test;
+
+import org.springframework.batch.item.ItemProcessor;
+import org.springframework.batch.item.support.ClassifierCompositeItemProcessor;
+import org.springframework.classify.PatternMatchingClassifier;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+
+/**
+ * @author Glenn Renfro
+ */
+public class ClassifierCompositeItemProcessorBuilderTests {
+
+	@Test
+	public void testBasicClassifierCompositeItemProcessor() throws Exception {
+
+		ItemProcessor<String, String> fooProcessor = item -> "foo: " + item;
+		ItemProcessor<String, String> defaultProcessor = item -> item;
+
+		Map<String, ItemProcessor<?, ? extends String>> routingConfiguration = new HashMap<>();
+		routingConfiguration.put("foo", fooProcessor);
+		routingConfiguration.put("*", defaultProcessor);
+		ClassifierCompositeItemProcessor<String, String> processor = new ClassifierCompositeItemProcessorBuilder<String, String>()
+				.classifier(new PatternMatchingClassifier<>(routingConfiguration))
+				.build();
+
+		assertEquals("bar", processor.process("bar"));
+		assertEquals("foo: foo", processor.process("foo"));
+		assertEquals("baz", processor.process("baz"));
+	}
+
+	@Test
+	public void testNullClassifier() {
+		try {
+			new ClassifierCompositeItemProcessorBuilder<String, String>().build();
+			fail("IllegalArgumentException should have been thrown");
+		}
+		catch (IllegalArgumentException iae) {
+			assertEquals("IllegalArgumentException message did not match the expected result.",
+					"A classifier is required.", iae.getMessage());
+		}
+	}
+}