POI 导出excel 时Cannot get a error value from a numeric cell

java.lang.IllegalStateException: Cannot get a error value from a numeric cell

	at org.apache.poi.xssf.streaming.SXSSFCell.typeMismatch(SXSSFCell.java:845)

	at org.apache.poi.xssf.streaming.SXSSFCell.getErrorCellValue(SXSSFCell.java:487)

	at org.apache.poi.xssf.streaming.SXSSFCell.convertCellValueToString(SXSSFCell.java:895)

	at org.apache.poi.xssf.streaming.SXSSFCell.setType(SXSSFCell.java:764)

	at org.apache.poi.xssf.streaming.SXSSFCell.ensureType(SXSSFCell.java:721)

	at org.apache.poi.xssf.streaming.SXSSFCell.setCellType(SXSSFCell.java:106)

	at com.zx.common.utils.msoffice.NewExcelHandle$StyleUtil.setCellValue(NewExcelHandle.java:222)

	at com.zx.common.utils.msoffice.NewExcelHandle$StyleUtil.setCellBorder(NewExcelHandle.java:456)

	at com.zx.outstock.service.OutStockService.WriteExcelFirstOutStockPhone(OutStockService.java:346)

	at com.zx.outstock.service.OutStockService.expAllLedgerDo(OutStockService.java:1495)

	at com.zx.outstock.service.OutStockService$$FastClassByCGLIB$$2fa33f31.invoke(<generated>)

	at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:191)

	at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:700)

	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)

	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)

	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)

	at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:635)

	at com.zx.outstock.service.OutStockService$$EnhancerByCGLIB$$fbba495b.expAllLedgerDo(<generated>)

用Poi的SXXFWorkbook导出excel2007的时候报的错，谁遇见过这个错误
------解决方案--------------------
应该是格子里是数字类型，但是没用数字类型去取

switch (cell.getCellType()) {

    		case Cell.CELL_TYPE_BLANK:

    			ret = "";

    			break;

    		case Cell.CELL_TYPE_BOOLEAN:

    			ret = String.valueOf(cell.getBooleanCellValue());

    			break;

    		case Cell.CELL_TYPE_ERROR:

    			ret = null;

    			break;

    		case Cell.CELL_TYPE_FORMULA:

    			Workbook wb = cell.getSheet().getWorkbook();

    			CreationHelper crat