easyexcel/src/main/java/com/alibaba/excel/write/style/column/LongestMatchColumnWidthStyleStrategy.java

package com.alibaba.excel.write.style.column;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.collections4.CollectionUtils;
import org.apache.poi.ss.usermodel.Cell;

import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.CellData;
import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;

/**
 * Take the width of the longest column as the width.
 * <p>
 * This is not very useful at the moment, for example if you have Numbers it will cause a newline.And the length is not
 * exactly the same as the actual length.
 *
 * @author Jiaju Zhuang
 */
public class LongestMatchColumnWidthStyleStrategy extends AbstractColumnWidthStyleStrategy {

    private static final int MAX_COLUMN_WIDTH = 255;

    private Map<Integer, Map<Integer, Integer>> cache = new HashMap<Integer, Map<Integer, Integer>>(8);

    @Override
    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<CellData> cellDataList, Cell cell, Head head,
        Integer relativeRowIndex, Boolean isHead) {
        boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);
        if (!needSetWidth) {
            return;
        }
        Map<Integer, Integer> maxColumnWidthMap = cache.get(writeSheetHolder.getSheetNo());
        if (maxColumnWidthMap == null) {
            maxColumnWidthMap = new HashMap<Integer, Integer>(16);
            cache.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);
        }
        Integer columnWidth = dataLength(cellDataList, cell, isHead);
        if (columnWidth < 0) {
            return;
        }
        if (columnWidth > MAX_COLUMN_WIDTH) {
            columnWidth = MAX_COLUMN_WIDTH;
        }
        Integer maxColumnWidth = maxColumnWidthMap.get(cell.getColumnIndex());
        if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
            maxColumnWidthMap.put(cell.getColumnIndex(), columnWidth);
            writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), columnWidth * 256);
        }
    }

    private Integer dataLength(List<CellData> cellDataList, Cell cell, Boolean isHead) {
        if (isHead) {
            return cell.getStringCellValue().getBytes().length;
        }
        CellData cellData = cellDataList.get(0);
        CellDataTypeEnum type = cellData.getType();
        if (type == null) {
            return -1;
        }
        switch (type) {
            case STRING:
                return cellData.getStringValue().getBytes().length;
            case BOOLEAN:
                return cellData.getBooleanValue().toString().getBytes().length;
            case NUMBER:
                return cellData.getNumberValue().toString().getBytes().length;
            default:
                return -1;
        }
    }
}