poi/src/java/org/apache/poi/hssf/eventusermodel/EventWorkbookBuilder.java

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   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You 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

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   distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.poi.hssf.eventusermodel;

import java.util.ArrayList;
import java.util.List;

import org.apache.poi.hssf.model.HSSFFormulaParser;
import org.apache.poi.hssf.model.Workbook;
import org.apache.poi.hssf.record.BoundSheetRecord;
import org.apache.poi.hssf.record.EOFRecord;
import org.apache.poi.hssf.record.ExternSheetRecord;
import org.apache.poi.hssf.record.Record;
import org.apache.poi.hssf.record.SSTRecord;
import org.apache.poi.hssf.record.SupBookRecord;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;

/**
 * When working with the EventUserModel, if you want to 
 *  process formulas, you need an instance of
 *  {@link Workbook} to pass to a {@link HSSFWorkbook},
 *  to finally give to {@link HSSFFormulaParser}, 
 *  and this will build you stub ones.
 * Since you're working with the EventUserModel, you
 *  wouldn't want to get a full {@link Workbook} and
 *  {@link HSSFWorkbook}, as they would eat too much memory.
 *  Instead, you should collect a few key records as they
 *  go past, then call this once you have them to build a
 *  stub {@link Workbook}, and from that a stub
 *  {@link HSSFWorkbook}, to use with the {@link HSSFFormulaParser}.
 * 
 * The records you should collect are:
 *  * {@link ExternSheetRecord}
 *  * {@link BoundSheetRecord}
 * You should probably also collect {@link SSTRecord}, 
 *  but it's not required to pass this in.
 *  
 * To help, this class includes a HSSFListener wrapper
 *  that will do the collecting for you.
 */
public class EventWorkbookBuilder {
	/**
	 * Wraps up your stub {@link Workbook} as a stub
	 *  {@link HSSFWorkbook}, ready for passing to
	 *  {@link HSSFFormulaParser}
	 * @param workbook A stub {@link Workbook}
	 */
	public static HSSFWorkbook createStubHSSFWorkbook(Workbook workbook) {
		return new StubHSSFWorkbook(workbook);
	}
	
	/**
	 * Creates a stub Workbook from the supplied records,
	 *  suitable for use with the {@link HSSFFormulaParser}
	 * @param externs The ExternSheetRecords in your file
	 * @param bounds The BoundSheetRecords in your file
	 * @param sst The SSTRecord in your file.
	 * @return A stub Workbook suitable for use with {@link HSSFFormulaParser}
	 */
	public static Workbook createStubWorkbook(ExternSheetRecord[] externs,
			BoundSheetRecord[] bounds, SSTRecord sst) {
		List wbRecords = new ArrayList();
		
		// Core Workbook records go first
		if(bounds != null) {
			for(int i=0; i<bounds.length; i++) {
				wbRecords.add(bounds[i]);
			}
		}
		if(sst != null) {
			wbRecords.add(sst);
		}
		
		// Now we can have the ExternSheetRecords,
		//  preceded by a SupBookRecord
		if(externs != null) {
			wbRecords.add(SupBookRecord.createInternalReferences(
					(short)externs.length));
			for(int i=0; i<externs.length; i++) {
				wbRecords.add(externs[i]);
			}
		}
		
		// Finally we need an EoF record
		wbRecords.add(EOFRecord.instance);
		
		return Workbook.createWorkbook(wbRecords);
	}
	
	/**
	 * Creates a stub workbook from the supplied records,
	 *  suitable for use with the {@link HSSFFormulaParser}
	 * @param externs The ExternSheetRecords in your file
	 * @param bounds The BoundSheetRecords in your file
	 * @return A stub Workbook suitable for use with {@link HSSFFormulaParser}
	 */
	public static Workbook createStubWorkbook(ExternSheetRecord[] externs,
			BoundSheetRecord[] bounds) {
		return createStubWorkbook(externs, bounds, null);
	}
	
	
	/**
	 * A wrapping HSSFListener which will collect 
	 *  {@link BoundSheetRecord}s and {@link ExternSheetRecord}s as
	 *  they go past, so you can create a Stub {@link Workbook} from
	 *  them once required.
	 */
	public static class SheetRecordCollectingListener implements HSSFListener {
		private HSSFListener childListener;
		private List boundSheetRecords = new ArrayList();
		private List externSheetRecords = new ArrayList();
		private SSTRecord sstRecord = null;
		
		public SheetRecordCollectingListener(HSSFListener childListener) {
			this.childListener = childListener;
		}
		
		
		public BoundSheetRecord[] getBoundSheetRecords() {
			return (BoundSheetRecord[])boundSheetRecords.toArray(
					new BoundSheetRecord[boundSheetRecords.size()]
			);
		}
		public ExternSheetRecord[] getExternSheetRecords() {
			return (ExternSheetRecord[])externSheetRecords.toArray(
					new ExternSheetRecord[externSheetRecords.size()]
			);
		}
		public SSTRecord getSSTRecord() {
			return sstRecord;
		}
		
		public HSSFWorkbook getStubHSSFWorkbook() {
			return createStubHSSFWorkbook(
					getStubWorkbook()
			);
		}
		public Workbook getStubWorkbook() {
			return createStubWorkbook(
					getExternSheetRecords(), getBoundSheetRecords(), 
					getSSTRecord()
			);
		}
		
		
		/**
		 * Process this record ourselves, and then
		 *  pass it on to our child listener
		 */
		public void processRecord(Record record) {
			// Handle it ourselves
			processRecordInternally(record);
			
			// Now pass on to our child
			childListener.processRecord(record);
		}
		
		/**
		 * Process the record ourselves, but do not
		 *  pass it on to the child Listener.
		 */
		public void processRecordInternally(Record record) {
			if(record instanceof BoundSheetRecord) {
				boundSheetRecords.add(record);
			}
			else if(record instanceof ExternSheetRecord) {
				externSheetRecords.add(record);
			}
			else if(record instanceof SSTRecord) {
				sstRecord = (SSTRecord)record;
			}
		}
	}
	
	/**
	 * Let us at the {@link Workbook} constructor on
	 *  {@link HSSFWorkbook}
	 */
	private static class StubHSSFWorkbook extends HSSFWorkbook {
		private StubHSSFWorkbook(Workbook wb) {
			super(wb);
		}
	}
}