Adds builder for MultiResourceItemReader

resolves BATCH-2604

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/file/MultiResourceItemReader.java

@@ -221,7 +221,8 @@ public class MultiResourceItemReader<T> extends AbstractItemStreamItemReader<T>
 	 * Set the boolean indicating whether or not state should be saved in the provided {@link ExecutionContext} during
 	 * the {@link ItemStream} call to update.
 	 * 
-	 * @param saveState
+	 * @param saveState true to update ExecutionContext. False do not update
+	 * ExecutionContext.
 	 */
 	public void setSaveState(boolean saveState) {
 		this.saveState = saveState;

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/file/builder/FlatFileItemReaderBuilder.java

@@ -385,7 +385,7 @@ public class FlatFileItemReaderBuilder<T> {
 	public FlatFileItemReader<T> build() throws Exception {
 		if(this.saveState) {
 			Assert.state(StringUtils.hasText(this.name),
-					"A name is required when saveSate is set to true.");
+					"A name is required when saveState is set to true.");
 		}
 
 		if(this.resource == null) {

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/file/builder/MultiResourceItemReaderBuilder.java

@@ -0,0 +1,167 @@
+/*
+ * 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.file.builder;
+
+import java.util.Comparator;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStream;
+import org.springframework.batch.item.file.MultiResourceItemReader;
+import org.springframework.batch.item.file.ResourceAwareItemReaderItemStream;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * A builder implementation for the {@link MultiResourceItemReader}.
+ *
+ * @author Glenn Renfro
+ * @since 4.0
+ * @see MultiResourceItemReader
+ */
+public class MultiResourceItemReaderBuilder<T> {
+
+	private ResourceAwareItemReaderItemStream<? extends T> delegate;
+
+	private Resource[] resources;
+
+	private boolean saveState = true;
+
+	private boolean strict = false;
+
+	private String name;
+
+	private Comparator<Resource> comparator;
+
+	/**
+	 * The array of resources that the {@link MultiResourceItemReader} will use to
+	 * retrieve items.
+	 *
+	 * @param resources the array of resources to use.
+	 * @return this instance for method chaining.
+	 *
+	 * @see MultiResourceItemReader#setResources(Resource[])
+	 */
+	public MultiResourceItemReaderBuilder<T> resources(Resource[] resources) {
+		this.resources = resources;
+
+		return this;
+	}
+
+	/**
+	 * Establishes the delegate to use for reading the resources provided.
+	 *
+	 * @param delegate reads items from single {@link Resource}.
+	 * @return this instance for method chaining.
+	 *
+	 * @see MultiResourceItemReader#setDelegate(ResourceAwareItemReaderItemStream)
+	 */
+	public MultiResourceItemReaderBuilder<T> delegate(ResourceAwareItemReaderItemStream<? extends T> delegate) {
+		this.delegate = delegate;
+
+		return this;
+	}
+
+	/**
+	 * Set the boolean indicating whether or not state should be saved in the provided
+	 * {@link ExecutionContext} during the {@link ItemStream} call to update.
+	 *
+	 * @param saveState true to update ExecutionContext. False do not update
+	 * ExecutionContext.
+	 * @return this instance for method chaining.
+	 * @see MultiResourceItemReader#setSaveState(boolean)
+	 * 
+	 */
+	public MultiResourceItemReaderBuilder<T> saveState(boolean saveState) {
+		this.saveState = saveState;
+
+		return this;
+	}
+
+	/**
+	 * In strict mode the reader will throw an exception on
+	 * {@link MultiResourceItemReader#open(org.springframework.batch.item.ExecutionContext)}
+	 * if there are no resources to read.
+	 *
+	 * @param strict false by default.
+	 * @return this instance for method chaining.
+	 * @see MultiResourceItemReader#setStrict(boolean)
+	 */
+	public MultiResourceItemReaderBuilder<T> setStrict(boolean strict) {
+		this.strict = strict;
+
+		return this;
+	}
+
+	/**
+	 * The name of the component which will be used as a stem for keys in the
+	 * {@link ExecutionContext}. Subclasses should provide a default value, e.g. the short
+	 * form of the class name.
+	 *
+	 * @param name the name for the component.
+	 * @return this instance for method chaining.
+	 * @see MultiResourceItemReader#setName(String)
+	 */
+	public MultiResourceItemReaderBuilder<T> name(String name) {
+		this.name = name;
+
+		return this;
+	}
+
+	/**
+	 * Used to order the injected resources, by default compares
+	 * {@link Resource#getFilename()} values.
+	 *
+	 * @param comparator the comparator to use for ordering resources.
+	 * @return this instance for method chaining.
+	 * @see MultiResourceItemReader#setComparator(Comparator)
+	 */
+	public MultiResourceItemReaderBuilder<T> comparator(Comparator<Resource> comparator) {
+		this.comparator = comparator;
+
+		return this;
+	}
+
+	/**
+	 * Builds the {@link MultiResourceItemReader}.
+	 *
+	 * @return a {@link MultiResourceItemReader}
+	 */
+	public MultiResourceItemReader<T> build() {
+		Assert.notNull(this.resources, "resources array is required.");
+		Assert.notNull(this.delegate, "delegate is required.");
+		if (this.saveState) {
+			Assert.state(StringUtils.hasText(this.name), "A name is required when saveState is set to true.");
+		}
+
+		MultiResourceItemReader<T> reader = new MultiResourceItemReader<>();
+		reader.setResources(this.resources);
+		reader.setDelegate(this.delegate);
+		reader.setSaveState(this.saveState);
+		reader.setStrict(this.strict);
+
+		if (comparator != null) {
+			reader.setComparator(this.comparator);
+		}
+		if (StringUtils.hasText(this.name)) {
+			reader.setName(this.name);
+		}
+
+		return reader;
+	}
+
+}