Add Builder for ClassifierCompositeItemWriter

resolves BATCH-2599

Added null check for setClassifier in ClassifierCompositeItemWriter.

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

@@ -24,6 +24,7 @@ import java.util.Map;
 import org.springframework.classify.Classifier;
 import org.springframework.classify.ClassifierSupport;
 import org.springframework.batch.item.ItemWriter;
+import org.springframework.util.Assert;
 
 /**
  * Calls one of a collection of ItemWriters for each item, based on a router
@@ -32,6 +33,7 @@ import org.springframework.batch.item.ItemWriter;
  * The implementation is thread-safe if all delegates are thread-safe.
  * 
  * @author Dave Syer
+ * @author Glenn Renfro
  * @since 2.0
  */
 public class ClassifierCompositeItemWriter<T> implements ItemWriter<T> {
@@ -42,6 +44,7 @@ public class ClassifierCompositeItemWriter<T> implements ItemWriter<T> {
 	 * @param classifier the classifier to set
 	 */
 	public void setClassifier(Classifier<T, ItemWriter<? super T>> classifier) {
+		Assert.notNull(classifier, "A classifier is required.");
 		this.classifier = classifier;
 	}
 

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

@@ -0,0 +1,63 @@
+/*
+ * 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.ItemWriter;
+import org.springframework.batch.item.support.ClassifierCompositeItemWriter;
+import org.springframework.classify.Classifier;
+import org.springframework.classify.ClassifierSupport;
+import org.springframework.util.Assert;
+
+/**
+ * Creates a fully qualified ClassifierCompositeItemWriter.
+ *
+ * @author Glenn Renfro
+ *
+ * @since 4.0
+ */
+public class ClassifierCompositeItemWriterBuilder<T> {
+
+	private Classifier<T, ItemWriter<? super T>> classifier;
+
+	/**
+	 * Establish the classifier to be used for the selection of which {@link ItemWriter}
+	 * to use.
+	 *
+	 * @param classifier the classifier to set
+	 * @return this instance for method chaining
+	 * @see org.springframework.batch.item.support.ClassifierCompositeItemWriter#setClassifier(Classifier)
+	 */
+	public ClassifierCompositeItemWriterBuilder<T> classifier(Classifier<T, ItemWriter<? super T>> classifier) {
+		this.classifier = classifier;
+
+		return this;
+	}
+
+	/**
+	 * Returns a fully constructed {@link ClassifierCompositeItemWriter}.
+	 *
+	 * @return a new {@link ClassifierCompositeItemWriter}
+	 */
+	public ClassifierCompositeItemWriter<T> build() {
+		Assert.notNull(classifier, "A classifier is required.");
+
+		ClassifierCompositeItemWriter<T> writer = new ClassifierCompositeItemWriter<>();
+		writer.setClassifier(this.classifier);
+		return writer;
+	}
+
+}

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.batch.item.support;
 
-import static org.junit.Assert.assertEquals;
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -24,11 +22,16 @@ import java.util.List;
 import java.util.Map;
 
 import org.junit.Test;
-import org.springframework.classify.PatternMatchingClassifier;
+
 import org.springframework.batch.item.ItemWriter;
+import org.springframework.classify.PatternMatchingClassifier;
+
+import static junit.framework.TestCase.fail;
+import static org.junit.Assert.assertEquals;
 
 /**
  * @author Dave Syer
+ * @author Glenn Renfro
  *
  */
 public class ClassifierCompositeItemWriterTests {
@@ -60,4 +63,16 @@ public class ClassifierCompositeItemWriterTests {
 		assertEquals("[one, two, three]", defaults.toString());
 	}
 
+	@Test
+	public void testSetNullClassifier() throws Exception {
+		try {
+			ClassifierCompositeItemWriter<String> writer = new ClassifierCompositeItemWriter<>();
+			writer.setClassifier(null);
+			fail("A classifier is required.");
+		}
+		catch (IllegalArgumentException iae) {
+			assertEquals("Message returned from exception did not match expected result.", "A classifier is required.",
+					iae.getMessage());
+		}
+	}
 }

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

@@ -0,0 +1,79 @@
+/*
+ * 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.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.Test;
+
+import org.springframework.batch.item.ItemWriter;
+import org.springframework.batch.item.support.ClassifierCompositeItemWriter;
+import org.springframework.classify.PatternMatchingClassifier;
+
+import static junit.framework.TestCase.fail;
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Glenn Renfro
+ */
+public class ClassifierCompositeItemWriterBuilderTests {
+
+	private List<String> defaults = new ArrayList<String>();
+
+	private List<String> foos = new ArrayList<String>();
+
+	@Test
+	public void testWrite() throws Exception {
+		Map<String, ItemWriter<? super String>> map = new HashMap<String, ItemWriter<? super String>>();
+		ItemWriter<String> fooWriter = new ItemWriter<String>() {
+			@Override
+			public void write(List<? extends String> items) throws Exception {
+				foos.addAll(items);
+			}
+		};
+		ItemWriter<String> defaultWriter = new ItemWriter<String>() {
+			@Override
+			public void write(List<? extends String> items) throws Exception {
+				defaults.addAll(items);
+			}
+		};
+		map.put("foo", fooWriter);
+		map.put("*", defaultWriter);
+		ClassifierCompositeItemWriter<String> writer = new ClassifierCompositeItemWriterBuilder<String>()
+				.classifier(new PatternMatchingClassifier<ItemWriter<? super String>>(map)).build();
+
+		writer.write(Arrays.asList("foo", "foo", "one", "two", "three"));
+		assertEquals("[foo, foo]", foos.toString());
+		assertEquals("[one, two, three]", defaults.toString());
+	}
+
+	@Test
+	public void testSetNullClassifier() throws Exception {
+		try {
+			new ClassifierCompositeItemWriterBuilder().build();
+			fail("A classifier is required.");
+		}
+		catch (IllegalArgumentException iae) {
+			assertEquals("Message returned from exception did not match expected result.", "A classifier is required.",
+					iae.getMessage());
+		}
+	}
+}