POI 合并后的框不完整

加上如下代码，妥妥的

RegionUtil.setBorderBottom(1, region, hssfSheet, wb);
RegionUtil.setBorderTop(1, region, hssfSheet, wb);
RegionUtil.setBorderLeft(1, region, hssfSheet, wb);
RegionUtil.setBorderRight(1, region, hssfSheet, wb);

至于参数内是什么，可以点进去看官方API