easyexcel 取消默认的表头样式

简化版本取消默认表头样式，点击跳转

easyexcel 默认导出的excel表头样式如上图，边框和背景色都设置了默认样式，源码如下：

com\alibaba\excel\util\StyleUtil.class

public static CellStyle buildDefaultCellStyle(Workbook workbook) {
    CellStyle newCellStyle = workbook.createCellStyle();
    newCellStyle.setWrapText(true);
    newCellStyle.setVerticalAlignment(VerticalAlignment.CENTER);
    newCellStyle.setAlignment(HorizontalAlignment.CENTER);
    newCellStyle.setLocked(true);
    newCellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);
    newCellStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
    newCellStyle.setBorderTop(BorderStyle.THIN);
    newCellStyle.setBorderBottom(BorderStyle.THIN);
    newCellStyle.setBorderLeft(BorderStyle.THIN);
    newCellStyle.setBorderRight(BorderStyle.THIN);
    return newCellStyle;
}

因为设置了背景色，所以无论怎么设置其他背景色和边框，都无法和内容样式保持一致。因为下方代码：

com\alibaba\excel\util\StyleUtil.class

if (writeCellStyle.getFillBackgroundColor() != null) {
    cellStyle.setFillBackgroundColor(writeCellStyle.getFillBackgroundColor());
}
if (writeCellStyle.getFillForegroundColor() != null) {
    cellStyle.setFillForegroundColor(writeCellStyle.getFillForegroundColor());
}

只要writeCellStyle.getFillBackgroundColor() != null或writeCellStyle.getFillForegroundColor() != null，边框就不会是默认的样式。即使把背景色设置为默认的IndexedColors.AUTOMATIC，边框全设置为BorderStyle.NONE也不行，这个时候没有边框。所以不能执行设置任何背景色的代码。

easyexcel中初始化表头样式和设置表头样式方法如下，initCellStyle会执行默认设置表头方法。如果要初始化initCellStyle方法会发现内容的样式初始化也在这个方法中，重写的话比较麻烦，所以决定只重写setHeadCellStyle方法。即使执行了initCellStyle方法也无妨，只要在重写的setHeadCellStyle中自定义表头样式即可，即覆盖掉默认表头样式。

com\alibaba\excel\write\style\HorizontalCellStyleStrategy.class

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@Override
protected void initCellStyle(Workbook workbook) {
    if (headWriteCellStyle != null) {
        headCellStyle = StyleUtil.buildHeadCellStyle(workbook, headWriteCellStyle);
    }
    if (contentWriteCellStyleList != null && !contentWriteCellStyleList.isEmpty()) {
        contentCellStyleList = new ArrayList<CellStyle>();
        for (WriteCellStyle writeCellStyle : contentWriteCellStyleList) {
            contentCellStyleList.add(StyleUtil.buildContentCellStyle(workbook, writeCellStyle));
        }
    }
}

@Override
protected void setHeadCellStyle(Cell cell, Head head, Integer relativeRowIndex) {
    if (headCellStyle == null) {
        return;
    }
    cell.setCellStyle(headCellStyle);
}

重写方法如下，ExcelStyleAnnotationCellWriteHandler为easyexcel 给单元格设置格式，通过自定义注解方式实现对每一列格式的精确控制中的类。样式的设置copy了com\alibaba\excel\util\StyleUtil.class中的方法，只是去掉了ishead参数。

@Slf4j
@Data
public class ExcelStyleAnnotationAndCancelDefaultHeadStyleCellWriteHandler extends ExcelStyleAnnotationCellWriteHandler {

    private WriteCellStyle headWriteCellStyleSelf;

    private CellStyle headCellStyleSelf;
    private Class c;

    public ExcelStyleAnnotationAndCancelDefaultHeadStyleCellWriteHandler(Class c, WriteCellStyle headWriteCellStyle, WriteCellStyle contentWriteCellStyle) {
        super(c,headWriteCellStyle, contentWriteCellStyle);
        this.headWriteCellStyleSelf = headWriteCellStyle;
    }

    @Override
    protected void setHeadCellStyle(Cell cell, Head head, Integer relativeRowIndex) {
        Workbook workbook = cell.getSheet().getWorkbook();
        headCellStyleSelf = buildHeadCellStyle(workbook, headWriteCellStyleSelf);
        if (headCellStyleSelf == null) {
            return;
        }
        cell.setCellStyle(headCellStyleSelf);
    }

    /**
     * Build head cell style
     */
    private static CellStyle buildHeadCellStyle(Workbook workbook, WriteCellStyle writeCellStyle) {
        CellStyle cellStyle = workbook.createCellStyle();
        if (writeCellStyle == null) {
            return cellStyle;
        }
        buildCellStyle(workbook, cellStyle, writeCellStyle);
        return cellStyle;
    }

    private static void buildCellStyle(Workbook workbook, CellStyle cellStyle, WriteCellStyle writeCellStyle) {
        buildFont(workbook, cellStyle, writeCellStyle.getWriteFont());
        if (writeCellStyle.getDataFormat() != null) {
            cellStyle.setDataFormat(writeCellStyle.getDataFormat());
        }
        if (writeCellStyle.getHidden() != null) {
            cellStyle.setHidden(writeCellStyle.getHidden());
        }
        if (writeCellStyle.getLocked() != null) {
            cellStyle.setLocked(writeCellStyle.getLocked());
        }
        if (writeCellStyle.getQuotePrefix() != null) {
            cellStyle.setQuotePrefixed(writeCellStyle.getQuotePrefix());
        }
        if (writeCellStyle.getHorizontalAlignment() != null) {
            cellStyle.setAlignment(writeCellStyle.getHorizontalAlignment());
        }
        if (writeCellStyle.getWrapped() != null) {
            cellStyle.setWrapText(writeCellStyle.getWrapped());
        }
        if (writeCellStyle.getVerticalAlignment() != null) {
            cellStyle.setVerticalAlignment(writeCellStyle.getVerticalAlignment());
        }
        if (writeCellStyle.getRotation() != null) {
            cellStyle.setRotation(writeCellStyle.getRotation());
        }
        if (writeCellStyle.getIndent() != null) {
            cellStyle.setIndention(writeCellStyle.getIndent());
        }
        if (writeCellStyle.getBorderLeft() != null) {
            cellStyle.setBorderLeft(writeCellStyle.getBorderLeft());
        }
        if (writeCellStyle.getBorderRight() != null) {
            cellStyle.setBorderRight(writeCellStyle.getBorderRight());
        }
        if (writeCellStyle.getBorderTop() != null) {
            cellStyle.setBorderTop(writeCellStyle.getBorderTop());
        }
        if (writeCellStyle.getBorderBottom() != null) {
            cellStyle.setBorderBottom(writeCellStyle.getBorderBottom());
        }
        if (writeCellStyle.getLeftBorderColor() != null) {
            cellStyle.setLeftBorderColor(writeCellStyle.getLeftBorderColor());
        }
        if (writeCellStyle.getRightBorderColor() != null) {
            cellStyle.setRightBorderColor(writeCellStyle.getRightBorderColor());
        }
        if (writeCellStyle.getTopBorderColor() != null) {
            cellStyle.setTopBorderColor(writeCellStyle.getTopBorderColor());
        }
        if (writeCellStyle.getBottomBorderColor() != null) {
            cellStyle.setBottomBorderColor(writeCellStyle.getBottomBorderColor());
        }
        if (writeCellStyle.getFillPatternType() != null) {
            cellStyle.setFillPattern(writeCellStyle.getFillPatternType());
        }
        if (writeCellStyle.getFillBackgroundColor() != null) {
            cellStyle.setFillBackgroundColor(writeCellStyle.getFillBackgroundColor());
        }
        if (writeCellStyle.getFillForegroundColor() != null) {
            cellStyle.setFillForegroundColor(writeCellStyle.getFillForegroundColor());
        }
        if (writeCellStyle.getShrinkToFit() != null) {
            cellStyle.setShrinkToFit(writeCellStyle.getShrinkToFit());
        }
    }

    private static void buildFont(Workbook workbook, CellStyle cellStyle, WriteFont writeFont) {
        Font font = workbook.createFont();
        font.setFontName("宋体");
        font.setFontHeightInPoints((short)14);
        font.setBold(true);
        cellStyle.setFont(font);
        if (writeFont == null) {
            return;
        }
        if (writeFont.getFontName() != null) {
            font.setFontName(writeFont.getFontName());
        }
        if (writeFont.getFontHeightInPoints() != null) {
            font.setFontHeightInPoints(writeFont.getFontHeightInPoints());
        }
        if (writeFont.getItalic() != null) {
            font.setItalic(writeFont.getItalic());
        }
        if (writeFont.getStrikeout() != null) {
            font.setStrikeout(writeFont.getStrikeout());
        }
        if (writeFont.getColor() != null) {
            font.setColor(writeFont.getColor());
        }
        if (writeFont.getTypeOffset() != null) {
            font.setTypeOffset(writeFont.getTypeOffset());
        }
        if (writeFont.getUnderline() != null) {
            font.setUnderline(writeFont.getUnderline());
        }
        if (writeFont.getCharset() != null) {
            font.setCharSet(writeFont.getCharset());
        }
        if (writeFont.getBold() != null) {
            font.setBold(writeFont.getBold());
        }
    }
}

注意：构造函数传入的表头样式不能设置背景色和边框