Adds builder for MultiResourceItemWriter.

resolves BATCH-2605

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

@@ -0,0 +1,157 @@
+/*
+ * 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 org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.file.MultiResourceItemWriter;
+import org.springframework.batch.item.file.ResourceAwareItemWriterItemStream;
+import org.springframework.batch.item.file.ResourceSuffixCreator;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+/**
+ * A builder implementation for the {@link MultiResourceItemWriter}.
+ *
+ * @author Glenn Renfro
+ * @since 4.0
+ * @see MultiResourceItemWriter
+ */
+public class MultiResourceItemWriterBuilder<T> {
+
+	private Resource resource;
+
+	private ResourceAwareItemWriterItemStream<? super T> delegate;
+
+	private int itemCountLimitPerResource = Integer.MAX_VALUE;
+
+	private ResourceSuffixCreator suffixCreator;
+
+	private boolean saveState = true;
+
+	private String name;
+
+	/**
+	 * Allows customization of the suffix of the created resources based on the index.
+	 *
+	 * @param suffixCreator the customizable ResourceSuffixCreator to use.
+	 * @return The current instance of the builder.
+	 * @see MultiResourceItemWriter#setResourceSuffixCreator(ResourceSuffixCreator)
+	 */
+	public MultiResourceItemWriterBuilder<T> resourceSuffixCreator(ResourceSuffixCreator suffixCreator) {
+		this.suffixCreator = suffixCreator;
+
+		return this;
+	}
+
+	/**
+	 * After this limit is exceeded the next chunk will be written into newly created
+	 * resource.
+	 *
+	 * @param itemCountLimitPerResource the max numbers of items to be written per chunk.
+	 * @return The current instance of the builder.
+	 * @see MultiResourceItemWriter#setItemCountLimitPerResource(int)
+	 */
+	public MultiResourceItemWriterBuilder<T> itemCountLimitPerResource(int itemCountLimitPerResource) {
+		this.itemCountLimitPerResource = itemCountLimitPerResource;
+
+		return this;
+	}
+
+	/**
+	 * Delegate used for actual writing of the output.
+	 * @param delegate The delegate to use for writing.
+	 * @return The current instance of the builder.
+	 * @see MultiResourceItemWriter#setDelegate(ResourceAwareItemWriterItemStream)
+	 */
+	public MultiResourceItemWriterBuilder<T> delegate(ResourceAwareItemWriterItemStream<? super T> delegate) {
+		this.delegate = delegate;
+
+		return this;
+	}
+
+	/**
+	 * Prototype for output resources. Actual output files will be created in the same
+	 * directory and use the same name as this prototype with appended suffix (according
+	 * to {@link MultiResourceItemWriter#setResourceSuffixCreator(ResourceSuffixCreator)}.
+	 *
+	 * @param resource the prototype resource to use as the basis for creating resources.
+	 * @return The current instance of the builder.
+	 * @see MultiResourceItemWriter#setResource(Resource)
+	 */
+	public MultiResourceItemWriterBuilder<T> resource(Resource resource) {
+		this.resource = resource;
+
+		return this;
+	}
+
+	/**
+	 * Set the boolean indicating whether or not state should be saved in the provided
+	 * {@link ExecutionContext} during the delegate call to update.
+	 *
+	 * @param saveState true to update ExecutionContext. False do not update
+	 * ExecutionContext.
+	 * @return The current instance of the builder.
+	 * @see MultiResourceItemWriter#setSaveState(boolean)
+	 */
+	public MultiResourceItemWriterBuilder<T> saveState(boolean saveState) {
+		this.saveState = saveState;
+
+		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 The current instance of the builder.
+	 * @see MultiResourceItemWriter#setName(String)
+	 */
+	public MultiResourceItemWriterBuilder<T> name(String name) {
+		this.name = name;
+
+		return this;
+	}
+
+	/**
+	 * Builds the {@link MultiResourceItemWriter}.
+	 *
+	 * @return a {@link MultiResourceItemWriter}
+	 */
+	public MultiResourceItemWriter<T> build() {
+		Assert.notNull(this.resource, "resource is required.");
+		Assert.notNull(this.delegate, "delegate is required.");
+
+		if(this.saveState) {
+			org.springframework.util.Assert.hasText(this.name, "A name is required when saveState is true.");
+		}
+
+		MultiResourceItemWriter<T> writer = new MultiResourceItemWriter<>();
+		writer.setResource(this.resource);
+		writer.setDelegate(this.delegate);
+		writer.setItemCountLimitPerResource(this.itemCountLimitPerResource);
+		if(this.suffixCreator != null) {
+			writer.setResourceSuffixCreator(this.suffixCreator);
+		}
+		writer.setSaveState(this.saveState);
+		writer.setName(this.name);
+
+		return writer;
+	}
+
+}