/*
    * Copyright 2006-2013 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.adapter;
  
  import java.util.Arrays;
  import java.util.List;
  
  import org.springframework.batch.item.ItemWriter;
  import org.springframework.beans.BeanWrapper;
  import org.springframework.beans.BeanWrapperImpl;
  import org.springframework.util.Assert;
  
  /**
   * Delegates processing to a custom method - extracts property values from item
   * object and uses them as arguments for the delegate method.
   *
   * @see ItemWriterAdapter
   *
   * @author Robert Kasanicky
   */
  public class PropertyExtractingDelegatingItemWriter<T> extends AbstractMethodInvokingDelegator<T> implements
  ItemWriter<T> {
  
  	private String[] fieldsUsedAsTargetMethodArguments;
  
  	/**
  	 * Extracts values from item's fields named in
  	 * fieldsUsedAsTargetMethodArguments and passes them as arguments to the
  	 * delegate method.
  	 */
  	@Override
  	public void write(List<? extends T> items) throws Exception {
  		for (T item : items) {
  
  			// helper for extracting property values from a bean
  			BeanWrapper beanWrapper = new BeanWrapperImpl(item);
  
  			Object[] methodArguments = new Object[fieldsUsedAsTargetMethodArguments.length];
  			for (int i = 0; i < fieldsUsedAsTargetMethodArguments.length; i++) {
  				methodArguments[i] = beanWrapper.getPropertyValue(fieldsUsedAsTargetMethodArguments[i]);
  			}
  
  			invokeDelegateMethodWithArguments(methodArguments);
  
  		}
  	}
  
  	@Override
  	public void afterPropertiesSet() throws Exception {
  		super.afterPropertiesSet();
  		Assert.notEmpty(fieldsUsedAsTargetMethodArguments);
  	}
  
  	/**
  	 * @param fieldsUsedAsMethodArguments the values of the these item's fields
  	 * will be used as arguments for the delegate method. Nested property values
  	 * are supported, e.g. <code>address.city</code>
  	 */
  	public void setFieldsUsedAsTargetMethodArguments(String[] fieldsUsedAsMethodArguments) {
  		this.fieldsUsedAsTargetMethodArguments = Arrays.asList(fieldsUsedAsMethodArguments).toArray(
  				new String[fieldsUsedAsMethodArguments.length]);
  	}
  
  }