java - 获取 SXSSFWorkbook 的文件大小

Question

有没有办法获取SXSSFWorkbook生成的Excel的大小。

我需要检查生成的文件的大小，并根据大小执行不同的操作，例如，如果大小较小，则直接发送电子邮件；如果大小超过一定限制，则上传到某个位置。

谢谢

Answer 1

一个简单的解决方案:您可以将工作簿写入文件，然后分析其大小。

Workbook wb = ...
try (OutputStream os = new FileOutputStream("sheet.xlsx")) {
    wb.write(os);
}
long len = new File("sheet.xlsx").length();
if (len > 1024_1024) {
    // upload
} else {
    // email
}

如果您想限制文件大小，并且超出此限制就会失败，您可以使用以下包装器包装 OutputStream:

public class LimitingOutputStream extends OutputStream {
    private final OutputStream stream;
    private final long limitInBytes;
    private final AtomicLong bytesWritten = new AtomicLong();

    public LimitingOutputStream(@NotNull OutputStream out, long limitInBytes) {
        stream = out;
        this.limitInBytes = limitInBytes;
    }

    @Override
    public void write(int b) throws IOException {
        increaseCounterAndValidateNotOverflown(1);
        stream.write(b);
    }

    @Override
    public void write(@NotNull byte[] b) throws IOException {
        increaseCounterAndValidateNotOverflown(b.length);
        stream.write(b);
    }

    @Override
    public void write(@NotNull byte[] b, int off, int len) throws IOException {
        increaseCounterAndValidateNotOverflown(len);
        stream.write(b, off, len);
    }

    @Override
    public void flush() throws IOException {
        stream.flush();
    }

    @Override
    public void close() throws IOException {
        stream.close();
    }

    private void increaseCounterAndValidateNotOverflown(int delta) throws IOException {
        long count = bytesWritten.addAndGet(delta);
        if (count > limitInBytes) {
            throw new IOException(String.format("Output stream overflown; only %d allowed, but tried to write %d bytes", limitInBytes, count));
        }
    }
}

像这样使用

try (OutputStream os = new LimitingOutputStream(new FileOutputStream("sheet.xlsx"), 1024_1024)) {