Added builder for FlatFileItemWriter

This commit adds a builder for the `FlatFileItemWriter`.

Resolves BATCH-2553

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

@@ -61,11 +61,14 @@ import org.springframework.util.ClassUtils;
 public class FlatFileItemWriter<T> extends AbstractItemStreamItemWriter<T> implements ResourceAwareItemWriterItemStream<T>,
 InitializingBean {
 
-	private static final boolean DEFAULT_TRANSACTIONAL = true;
+	public static final boolean DEFAULT_TRANSACTIONAL = true;
 
 	protected static final Log logger = LogFactory.getLog(FlatFileItemWriter.class);
 
-	private static final String DEFAULT_LINE_SEPARATOR = System.getProperty("line.separator");
+	public static final String DEFAULT_LINE_SEPARATOR = System.getProperty("line.separator");
+
+	// default encoding for writing to output files - set to UTF-8.
+	public static final String DEFAULT_CHARSET = "UTF-8";
 
 	private static final String WRITTEN_STATISTICS_NAME = "written";
 
@@ -85,7 +88,7 @@ InitializingBean {
 
 	private boolean shouldDeleteIfEmpty = false;
 
-	private String encoding = OutputState.DEFAULT_CHARSET;
+	private String encoding = DEFAULT_CHARSET;
 
 	private FlatFileHeaderCallback headerCallback;
 
@@ -397,8 +400,6 @@ InitializingBean {
 	 * operations on the writer go through this class.
 	 */
 	private class OutputState {
-		// default encoding for writing to output files - set to UTF-8.
-		private static final String DEFAULT_CHARSET = "UTF-8";
 
 		private FileOutputStream os;
 

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

@@ -0,0 +1,268 @@
+/*
+ * Copyright 2016 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.file.FlatFileFooterCallback;
+import org.springframework.batch.item.file.FlatFileHeaderCallback;
+import org.springframework.batch.item.file.FlatFileItemWriter;
+import org.springframework.batch.item.file.transform.LineAggregator;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+/**
+ * A builder implementation for the {@link FlatFileItemWriter}
+ *
+ * @author Michael Minella
+ * @since 4.0
+ * @see FlatFileItemWriter
+ */
+public class FlatFileItemWriterBuilder<T> {
+
+	private Resource resource;
+
+	private boolean forceSync = false;
+
+	private String lineSeparator = FlatFileItemWriter.DEFAULT_LINE_SEPARATOR;
+
+	private LineAggregator<T> lineAggregator;
+
+	private String encoding = FlatFileItemWriter.DEFAULT_CHARSET;
+
+	private boolean shouldDeleteIfExists = true;
+
+	private boolean append = false;
+
+	private boolean shouldDeleteIfEmpty = false;
+
+	private boolean saveState = true;
+
+	private FlatFileHeaderCallback headerCallback;
+
+	private FlatFileFooterCallback footerCallback;
+
+	private boolean transactional = FlatFileItemWriter.DEFAULT_TRANSACTIONAL;
+
+	private String name;
+
+	/**
+	 * The name used to calculate the key within the
+	 * {@link org.springframework.batch.item.ExecutionContext}.  Required if
+	 * {@link FlatFileItemWriterBuilder#saveState(boolean)} is set to true.
+	 *
+	 * @param name name of the writer instance
+	 * @return The current instance of the builder.
+	 * @see FlatFileItemWriter#setName(String)
+	 */
+	public FlatFileItemWriterBuilder<T> name(String name) {
+		this.name = name;
+
+		return this;
+	}
+
+	/**
+	 * The {@link Resource} to be used as output.
+	 *
+	 * @param resource the output of the writer.
+	 * @return The current instance of the builder.
+	 * @see FlatFileItemWriter#setResource(Resource)
+	 */
+	public FlatFileItemWriterBuilder<T> resource(Resource resource) {
+		this.resource = resource;
+
+		return this;
+	}
+
+	/**
+	 * A flag indicating that changes should be force-synced to disk on flush.  Defaults
+	 * to false.
+	 *
+	 * @param forceSync value to set the flag to
+	 * @return The current instance of the builder.
+	 * @see FlatFileItemWriter#setForceSync(boolean)
+	 */
+	public FlatFileItemWriterBuilder<T> forceSync(boolean forceSync) {
+		this.forceSync = forceSync;
+
+		return this;
+	}
+
+	/**
+	 * String used to separate lines in output.  Defaults to the System property
+	 * line.separator.
+	 *
+	 * @param lineSeparator value to use for a line separator
+	 * @return The current instance of the builder.
+	 * @see FlatFileItemWriter#setLineSeparator(String)
+	 */
+	public FlatFileItemWriterBuilder<T> lineSeparator(String lineSeparator) {
+		this.lineSeparator = lineSeparator;
+
+		return this;
+	}
+
+	/**
+	 * Line aggregator used to build the String version of each item.
+	 *
+	 * @param lineAggregator {@link LineAggregator} implementation
+	 * @return The current instance of the builder.
+	 * @see FlatFileItemWriter#setLineAggregator(LineAggregator)
+	 */
+	public FlatFileItemWriterBuilder<T> lineAggregator(LineAggregator<T> lineAggregator) {
+		this.lineAggregator = lineAggregator;
+
+		return this;
+	}
+
+	/**
+	 * Encoding used for output.
+	 *
+	 * @param encoding encoding type.
+	 * @return The current instance of the builder.
+	 * @see FlatFileItemWriter#setEncoding(String)
+	 */
+	public FlatFileItemWriterBuilder<T> encoding(String encoding) {
+		this.encoding = encoding;
+
+		return this;
+	}
+
+	/**
+	 * If set to true, once the step is complete, if the resource previously provdied is
+	 * empty, it will be deleted.
+	 *
+	 * @param shouldDelete defaults to false
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setShouldDeleteIfEmpty(boolean)
+	 */
+	public FlatFileItemWriterBuilder<T> shouldDeleteIfEmpty(boolean shouldDelete) {
+		this.shouldDeleteIfEmpty = shouldDelete;
+
+		return this;
+	}
+
+	/**
+	 * If set to true, upon the start of the step, if the resource already exists, it will
+	 * be deleted and recreated.
+	 *
+	 * @param shouldDelete defaults to true
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setShouldDeleteIfExists(boolean)
+	 */
+	public FlatFileItemWriterBuilder<T> shouldDeleteIfExists(boolean shouldDelete) {
+		this.shouldDeleteIfExists = shouldDelete;
+
+		return this;
+	}
+
+	/**
+	 * If set to true and the file exists, the output will be appended to the existing
+	 * file.
+	 *
+	 * @param append defaults to false
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setAppendAllowed(boolean)
+	 */
+	public FlatFileItemWriterBuilder<T> append(boolean append) {
+		this.append = append;
+
+		return this;
+	}
+
+	/**
+	 * If set to false, the state of the output is not maintained and restart is not
+	 * supported.
+	 *
+	 * @param saveState defaults to true
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setSaveState(boolean)
+	 */
+	public FlatFileItemWriterBuilder<T> saveState(boolean saveState) {
+		this.saveState = saveState;
+
+		return this;
+	}
+
+	/**
+	 * A callback for header processing.
+	 *
+	 * @param callback {@link FlatFileHeaderCallback} impl
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setHeaderCallback(FlatFileHeaderCallback)
+	 */
+	public FlatFileItemWriterBuilder<T> headerCallback(FlatFileHeaderCallback callback) {
+		this.headerCallback = callback;
+
+		return this;
+	}
+
+	/**
+	 * A callback for footer processing
+	 * @param callback {@link FlatFileFooterCallback} impl
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setFooterCallback(FlatFileFooterCallback)
+	 */
+	public FlatFileItemWriterBuilder<T> footerCallback(FlatFileFooterCallback callback) {
+		this.footerCallback = callback;
+
+		return this;
+	}
+
+	/**
+	 * If set to true, the flushing of the buffer is delayed while a transaction is active.
+	 *
+	 * @param transactional defaults to true
+	 * @return The current instance of the builder
+	 * @see FlatFileItemWriter#setTransactional(boolean)
+	 */
+	public FlatFileItemWriterBuilder<T> transactional(boolean transactional) {
+		this.transactional = transactional;
+
+		return this;
+	}
+
+	/**
+	 * Validates and builds a {@link FlatFileItemWriter}.
+	 *
+	 * @return a {@link FlatFileItemWriter}
+	 */
+	public FlatFileItemWriter<T> build() {
+
+		Assert.notNull(this.lineAggregator, "A LineAggregator is required");
+		Assert.notNull(this.resource, "A Resource is required");
+
+		if(this.saveState) {
+			Assert.hasText(this.name, "A name is required when saveState is true");
+		}
+
+		FlatFileItemWriter<T> writer = new FlatFileItemWriter<>();
+
+		writer.setName(this.name);
+		writer.setAppendAllowed(this.append);
+		writer.setEncoding(this.encoding);
+		writer.setFooterCallback(this.footerCallback);
+		writer.setForceSync(this.forceSync);
+		writer.setHeaderCallback(this.headerCallback);
+		writer.setLineAggregator(this.lineAggregator);
+		writer.setLineSeparator(this.lineSeparator);
+		writer.setResource(this.resource);
+		writer.setSaveState(this.saveState);
+		writer.setShouldDeleteIfEmpty(this.shouldDeleteIfEmpty);
+		writer.setShouldDeleteIfExists(this.shouldDeleteIfExists);
+		writer.setTransactional(this.transactional);
+
+		return writer;
+	}
+}