grails - 无法将类 'jxl.biff.EmptyCell@47821b4b'的对象 'jxl.biff.EmptyCell'强制转换为类 'jxl.DateCell'

Question

我的域模型

package sample

class Person {

String lastName
String firstName
Date dateOfBirth
int numberOfChildren
static constraints = {
}
} 

我的 Controller

package sample

/*imported libraries.*/

import jxl.DateCell
import jxl.LabelCell
import jxl.NumberCell
import jxl.Sheet
import jxl.Workbook

class PersonController {
private final static int COLUMN_LAST_NAME = 0
private final static int COLUMN_FIRST_NAME = 1
private final static int COLUMN_DATE_OF_BIRTH = 2
private final static int COLUMN_NUMBER_OF_CHILDREN = 3

 def index() {
    redirect(action: "list", params: params)
}

def list(Integer max) {
    params.max = Math.min(max ?: 10, 100)
    [personInstanceList: Person.list(params), personInstanceTotal: Person.count()]
}

def upload() { }


    def doUpload() {
    def file = request.getFile('file')
    Workbook workbook = Workbook.getWorkbook(file.getInputStream());
    Sheet sheet = workbook.getSheet(0);

    // skip first row (row 0) by starting from 1
    for (int row = 1; row < sheet.getRows(); row++) {
        LabelCell lastName = sheet.getCell(COLUMN_LAST_NAME, row)
        LabelCell firstName = sheet.getCell(COLUMN_FIRST_NAME, row)
        DateCell dateOfBirth = sheet.getCell(COLUMN_DATE_OF_BIRTH, row)
        NumberCell numberOfChildren = sheet.getCell(COLUMN_NUMBER_OF_CHILDREN, row)

        new Person(lastName:lastName.string , firstName:firstName.string ,
                dateOfBirth:dateOfBirth.date, numberOfChildren:numberOfChildren.value).save()

    }
    redirect (action:'list')
}


} 

我想从grails数据库中的.xls文件加载数据，问题是未保存xls文件加载数据，并且出现以下错误。
无法将类别为'jxl.biff.EmptyCell'的对象'jxl.biff.EmptyCell@47821b4b'转换为类别'jxl.DateCell'。

Answer 1

在某些情况下，dateOfBirth似乎没有任何值。在这种情况下，空值不能转换为日期。这就是抛出can not cast class 'jxl.biff.EmptyCell' to class 'jxl.DateCell'的原因。

当dateOfBirth单元为空时，请确保将null设置为dataOfBirth。如果您对dateOfBirth字段有限制，它将自动引发exception。

空的constraints表示Person类中的所有属性都是必需的。显然，Excel工作表中存在空白字段，这会导致整个过程停止。如果您仍然希望忽略那些具有空字段的行并仍然处理好行，则可以执行以下一项或两项操作:

检查每个字段是否为空，然后继续调用以处理下一行。这是我的建议。

与/或

在try / catch中包装循环:

    for (int row = 1; row < sheet.getRows(); row++) {
        try{
                LabelCell lastName = sheet.getCell(COLUMN_LAST_NAME, row)
                LabelCell firstName = sheet.getCell(COLUMN_FIRST_NAME, row)
                DateCell dateOfBirth = sheet.getCell(COLUMN_DATE_OF_BIRTH, row)
                NumberCell numberOfChildren = sheet.getCell(COLUMN_NUMBER_OF_CHILDREN, row)
new Person(lastName:lastName.string , firstName:firstName.string ,
                        dateOfBirth:dateOfBirth.date, numberOfChildren:numberOfChildren.value).save(failOnError: true)
        }catch(e){
          // log the error and the row number so that you know which row failed
        }

    }

为了更好地了解哪个字段验证失败，请编写正确的字段验证错误消息。