Programmer-yyds commented on issue #879:
URL: https://github.com/apache/poi/issues/879#issuecomment-3187289187
# Apache POI Temporary Files Not Deleted in Multi-Threaded Environment
## Steps to Reproduce
Run the following code example:
```
import org.apache.poi.openxml4j.opc.ZipPackage;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.util.IOUtils;
import org.apache.poi.xssf.usermodel.*;
import java.io.*;
import java.util.concurrent.atomic.AtomicInteger;
public class ExcelImageWriter {
private final XSSFWorkbook workbook;
private final XSSFSheet sheet;
private final AtomicInteger rowIndex = new AtomicInteger(0);
private final String outputPath;
private final XSSFDrawing drawing;
static {
// Enable temporary file mode
ZipPackage.setUseTempFilePackageParts(true);
// Specifies the temporary file directory (default is /tmp on Linux)
System.setProperty("java.io.tmpdir",
"/Users/shanjiacong/Desktop/temp");
}
public ExcelImageWriter(String outputPath) {
this.workbook = new XSSFWorkbook();
this.sheet = workbook.createSheet("Images");
this.outputPath = outputPath;
this.drawing = sheet.createDrawingPatriarch();
sheet.setColumnWidth(0, 30 * 256);
}
public void addImage(byte[] bytes) throws IOException {
int pictureIndex = workbook.addPicture(bytes,
Workbook.PICTURE_TYPE_PNG);
CreationHelper helper = workbook.getCreationHelper();
int rowNum = rowIndex.getAndIncrement();
XSSFClientAnchor anchor = (XSSFClientAnchor)
helper.createClientAnchor();
anchor.setCol1(0);
anchor.setRow1(rowNum);
anchor.setCol2(1);
anchor.setRow2(rowNum + 1);
drawing.createPicture(anchor, pictureIndex);
Row row = sheet.getRow(rowNum);
if (row == null) {
row = sheet.createRow(rowNum);
}
row.setHeightInPoints(100);
}
public void save() throws IOException {
try (FileOutputStream fos = new FileOutputStream(outputPath)) {
workbook.write(fos);
}
workbook.close();
}
public static void main(String[] args) throws Exception {
ExcelImageWriter writer = new
ExcelImageWriter("/Users/shanjiacong/Desktop/temp/output.xlsx");
byte [] bytes;
try {
// Read local image as byte[]
bytes =
readImageBytes("/Users/shanjiacong/Downloads/wps-excel-embed-image-main/test02.jpg");
} catch (IOException e) {
throw new RuntimeException(e);
}
// Simulate adding multiple images
for (int i = 0; i < 5; i++) {
writer.addImage(bytes);
}
writer.save();
System.out.println("writeCompleted！");
}
private static byte[] readImageBytes(String path) throws IOException {
try (InputStream is = new FileInputStream(path)) {
return IOUtils.toByteArray(is);
}
}
}
```
1. Prepare an image file (e.g., `test02.jpg`) and update the path in the
code.
2. Run the program.
3. Observe the temporary file directory (e.g., `/tmp` or the custom path set
by `java.io.tmpdir`).
4. Repeat execution several times — the number of temporary files will keep
growing and are not deleted after the process ends.
## Impact
- A large number of temporary files occupy disk space, potentially
exhausting container storage.
- **With repeated runs, temporary files keep accumulating, increasing disk
usage over time.**
## Temporary Workaround & Limitations
- Manually clean up temporary files, but with the following issues:
- In a multi-threaded environment, all threads write temporary files to
the same directory.
- Cannot distinguish between files from completed exports and those still
being generated.
- Deleting files blindly may corrupt files still in creation.
## Expected Behavior
- Temporary files should be automatically deleted after the program ends.
- Multi-threaded runs should not interfere with each other's temporary files.
## Actual Behavior
- Temporary files remain in the directory even after the program finishes.
- Repeated executions cause the temporary file count to grow continuously.
## Screenshots
The program will create POI files in the temporary directory as shown below:
<img width="175" height="170" alt="Image"
src="https://github.com/user-attachments/assets/11cd7817-e89c-4e78-a6e3-0a4166b5bd50";
/>
Temporary files generated by running the program for the first time:
<img width="746" height="403" alt="Image"
src="https://github.com/user-attachments/assets/245d5645-f560-49ca-a2d8-c020533da5d1";
/>
Temporary files generated by running the program for the second time:
<img width="705" height="537" alt="Image"
src="https://github.com/user-attachments/assets/23dd490e-f6ff-4d0e-bed7-3064f53abd29";
/>
**Observation:** Temporary files are not deleted after the whole program
stops.
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