接口的使用
com.alibaba.excel.event.Handler

intercepts handle cell creation

intercepts handle sheet creation

intercepts handle excel write

已过时。 

已过时。 

Default row handler.

fill cell style.

Merge strategy

It only merges once when create cell(firstRowIndex,lastRowIndex)

Cell style strategy

The default styles

Column width style strategy

Take the width of the longest column as the width.

Set the row height strategy