为什么使用 XSSFWorkbook 会修改原始文件？

我目前在 Jira Scriptrunner 中使用 Groovy。我正在使用 apache 中的 XSSFWorkbook。在脚本中，我加载一个“模板”.xslx 文件，然后使用脚本对其进行修改。尽管该文件从未以相同的文件名保存到服务器，但仅workbook.write(outputStream)被workbook.close()调用，服务器上的原始文件已被修改。

以下是代码：

import org.apache.poi.xssf.usermodel.XSSFWorkbook
import releasemanagement.changes.AttachmentCreator
import other.TMPConfig
import com.atlassian.jira.issue.fields.CustomField
import com.atlassian.jira.issue.CustomFieldManager
import com.atlassian.jira.component.ComponentAccessor
import org.apache.poi.xssf.usermodel.XSSFCell

CustomFieldManager custFldManag = ComponentAccessor.getCustomFieldManager()

def issue = Issues.getByKey("ISSUEKEY")

def attachmentCreator = new AttachmentCreator()
def attachmentManager = ComponentAccessor.getAttachmentManager()

def wb = new XSSFWorkbook(new File("path/Template.xlsx"))

CustomField currCF
XSSFCell currCell
String reportType = "Initial"

TMPConfig.fieldToCell.each{k, v ->
    List<Integer> cellCoordinates = v.get(reportType)
    if(cellCoordinates){
        currCell = wb.getSheetAt(cellCoordinates[0]).getRow(cellCoordinates[1]).getCell(cellCoordinates[2])
        if(currCell){
            currCF = custFldManag.getCustomFieldObject(k)
            currCell.setCellValue(currCF.getValue(issue).toString())
        }
    }
}

ByteArrayOutputStream out = new ByteArrayOutputStream()
wb.write(out)
wb.close()
ByteArrayInputStream inputStream = new ByteArrayInputStream(out.toByteArray())
out.close()

int filename_num = 1
String filename = "Dora_${reportType}_${filename_num}.xlsx"

attachmentCreator.createAttachmentForIssue(issue, filename, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", inputStream)

目前，这个问题已由我的同事通过以下解决方法解决：

XSSFWorkbook wb_temp = new XSSFWorkbook(new File("path/Template.xlsx"))
    ByteArrayOutputStream out_temp = new ByteArrayOutputStream()
        wb_temp.write(out_temp)
        wb_temp.close()
    ByteArrayInputStream inputStream_temp = new ByteArrayInputStream(out_temp.toByteArray())
        out_temp.close()
    XSSFWorkbook wb = new XSSFWorkbook(inputStream_temp)

但我对这种行为的原因很感兴趣。我希望当它附加到问题中时，内存中的表示不会影响原始文件。感谢您的任何见解。