https://issues.apache.org/bugzilla/show_bug.cgi?id=56563
Bug ID: 56563
Summary: Multithreading bug when reading 2 similar files
Product: POI
Version: 3.10
Hardware: All
OS: All
Status: NEW
Severity: major
Priority: P2
Component: HSSF
Assignee: [email protected]
Reporter: [email protected]
Created attachment 31660
--> https://issues.apache.org/bugzilla/attachment.cgi?id=31660&action=edit
A file for which the problem reproduces
When reading two copies of the same file (doesn't necessarily need to be the
exact same file, but do need to contain the same styles or something along
those lines),
from two threads simultaneously (each thread processes its own file), the
format string of cell styles get mixed up.
The following code demonstrates this, printing to System.out every time a non
date cell is mistakenly recognized as date. Note that starting only one of the
threads yields no System.out messages.
public class CellFormatBugExample implements Runnable {
public static void main(String[] args) {
new Thread(new CellFormatBugExample("C:/temp/file_1.xls")).start();
new Thread(new CellFormatBugExample("C:/temp/file_2.xls")).start();
}
String filePath;
public CellFormatBugExample(String filePath) {
this.filePath = filePath;
}
@Override
public void run() {
File inputFile = new File(filePath);
try (FileInputStream stream = new FileInputStream(inputFile)) {
Workbook wb = WorkbookFactory.create(stream);
Sheet sheet = wb.getSheetAt(0);
for (Row row : sheet) {
for (Integer idxCell = 0; idxCell < row.getLastCellNum();
idxCell++) {
Cell cell = row.getCell(idxCell);
cell.getCellStyle().getDataFormatString();
if (cell.getCellType() == HSSFCell.CELL_TYPE_NUMERIC) {
boolean isDate =
HSSFDateUtil.isCellDateFormatted(cell);
if (idxCell > 0 && isDate) {
System.out.println("cell " + idxCell + " is not a
date!");
}
}
}
}
}
catch (Exception e) {
e.printStackTrace();
}
}
}
Make another copy of the attached file - "file_2.xls" and run the code to
reproduce.
Digging around a bit, seems the cause for this is a caching bug in the
HSSFCellStyle.getDataFormatString() method.
As far as I could understand a simple resolution would be to synchronize access
to that method.
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