Use the streaming mode of hutool to read large Excel files

website ： 

In standard ExcelReader in , If the amount of data is large , Read Excel It's going to be very slow , And may cause memory overflow . So for the large amount of data Excel,Hutool Encapsulates the Sax How to read patterns .

Excel07SaxReader Support Excel2007 Format Sax Read .

Refer to the experience of others' blogs , The following tools are summarized ExcelKit： ( The complete code of the class is as follows ）

package com.xxx.app.blog.common.kit;

import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.bean.copier.CopyOptions;
import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.lang.Console;
import cn.hutool.core.util.ReflectUtil;
import cn.hutool.poi.excel.sax.Excel07SaxReader;
import cn.hutool.poi.excel.sax.handler.RowHandler;
import java.util.*;

/**
 * ExcelKit excel File processing library , rely on Hutool
 */
public class ExcelKit {

	private static List<Object> headLine;
	private static List<Map<String, Object>> datas = new ArrayList<>();

	/**
	 * @param pathAndName         File path 
	 * @param idOrRidOrSheetName Excel Medium sheet id perhaps rid Number or sheet name ,rid Must be added rId Prefix , for example rId1, If -1 Process all numbered sheet
	 */
	public static List<Map<String, Object>> readBigExcel(String pathAndName, int idOrRidOrSheetName) {
		Console.log("【{}】  Start reading  ... ", pathAndName);
		datas.clear();
		Excel07SaxReader reader = new Excel07SaxReader(new MyRowHandler());
		reader.read(pathAndName, idOrRidOrSheetName);
		Console.log("【{}】  Read complete  ... ", pathAndName);
		return datas;
	}

	/**
	 * @param pathAndName         File path 
	 * @param idOrRidOrSheetName Excel Medium sheet id perhaps rid Number or sheet name ,rid Must be added rId Prefix , for example rId1, If -1 Process all numbered sheet
	 * @param beanType            Class types 
	 * @param <T>                 The return value is List<T>
	 * @return
	 */
	public static <T> List<T> read(String pathAndName, int idOrRidOrSheetName, Class<T> beanType) {
		return read(pathAndName, idOrRidOrSheetName, beanType, Collections.EMPTY_MAP);
	}

	/**
	 * @param pathAndName         File path 
	 * @param idOrRidOrSheetName Excel Medium sheet id perhaps rid Number or sheet name ,rid Must be added rId Prefix , for example rId1, If -1 Process all numbered sheet
	 * @param beanType            Class types 
	 * @param fieldMapping       T Alias corresponding to type , That is... Corresponding to class type  excel  The relationship between 
	 * @param <T>                 The return value is List<T>
	 * @return
	 */
	public static <T> List<T> read(String pathAndName, int idOrRidOrSheetName, Class<T> beanType, Map<String, String> fieldMapping) {
		CopyOptions copyOptions = CopyOptions.create();
		if (CollUtil.isNotEmpty(fieldMapping)) {
			copyOptions.setFieldMapping(fieldMapping);
		}
		readBigExcel(pathAndName, idOrRidOrSheetName);
		List<T> datalist = new ArrayList<>();
		for (Map<String, Object> data : datas) {
			T t = ReflectUtil.newInstanceIfPossible(beanType);
			datalist.add(BeanUtil.fillBeanWithMap(data, t, copyOptions));
		}
		return datalist;
	}

	private static class MyRowHandler implements RowHandler {
		@Override
		public void handle(int sheetIndex, long rowIndex, List<Object> rowList) {
			//Console.log("[{}] [{}] {}", sheetIndex, rowIndex, rowList);
			if (rowIndex == 0) {
				headLine = rowList;
			} else {
				Map<String, Object> tMap = new HashMap<>(rowList.size());
				for (int i = 0; i < rowList.size(); i++) {
					tMap.put(transStr(headLine.get(i)), rowList.get(i));
				}
				datas.add(tMap);
			}
		}
	}

	private static String transStr(Object obj) {
		return obj == null ? "" : obj.toString();
	}
}

Access usage ：

// Large amount of data excel Read mode 
List<Map<String,Object>> recordBMapList = null;
recordBMapList = ExcelKit.readBigExcel(" File path ",-1);
// The second parameter ,-1 Represents reading all sheet data ;0 Represents reading the first sheet data , By analogy ;