OPEN - BATCH-932: Add reflection-based Field Extractor

applied patch with minor tweaks

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

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2006-2007 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.transform;
+
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.Assert;
+
+/**
+ * This is a delimited line aggregator for a java bean. Given an array of
+ * property names, it will reflectively call getters on the item to aggregate.
+ * 
+ * @author Dan Garrette
+ * @since 2.0
+ */
+public class BeanDelimitingLineAggregator<T> implements LineAggregator<T>, InitializingBean {
+
+	private BeanWrapperFieldExtractor<T> extractor;
+
+	private DelimitedLineAggregator<Object> delimitedLineAggregator = new DelimitedLineAggregator<Object>();
+
+	/**
+	 * @param names names of properties of the aggregated item that will be
+	 * included in the resulting string. Must not be <code>null</code>.
+	 */
+	public void setNames(String[] names) {
+		extractor = new BeanWrapperFieldExtractor<T>();
+		extractor.setNames(names);
+		extractor.afterPropertiesSet();
+	}
+
+	/**
+	 * @param delimiter used to separate property values in the
+	 * {@link #aggregate(Object)} result
+	 */
+	public void setDelimiter(String delimiter) {
+		this.delimitedLineAggregator.setDelimiter(delimiter);
+	}
+
+	public String aggregate(T item) {
+		Object[] fields = this.extractor.extract(item);
+		return this.delimitedLineAggregator.aggregate(fields);
+	}
+
+	public void afterPropertiesSet() throws Exception {
+		Assert.notNull(this.extractor, "The 'names' property must be set.");
+	}
+}

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

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2006-2007 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.transform;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.beans.BeanWrapper;
+import org.springframework.beans.BeanWrapperImpl;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.Assert;
+
+/**
+ * This is a field extractor for a java bean. Given an array of property names,
+ * it will reflectively call getters on the item and return an array of all the
+ * values.
+ * 
+ * @author Dan Garrette
+ * @since 2.0
+ */
+public class BeanWrapperFieldExtractor<T> implements FieldExtractor<T>, InitializingBean {
+
+	private String[] names;
+
+	/**
+	 * @param names field names to be extracted by the {@link #extract(Object)} method.
+	 */
+	public void setNames(String[] names) {
+		this.names = names;
+	}
+
+	/**
+	 * @see org.springframework.batch.item.file.transform.FieldExtractor#extract(java.lang.Object)
+	 */
+	public Object[] extract(T item) {
+		List<Object> values = new ArrayList<Object>();
+
+		BeanWrapper bw = new BeanWrapperImpl(item);
+		for (String propertyName : this.names) {
+			values.add(bw.getPropertyValue(propertyName));
+		}
+		return values.toArray();
+	}
+
+	public void afterPropertiesSet() {
+		Assert.notNull(names, "The 'names' property must be set.");
+	}
+}