java 生成表格并添加水印

为了生成表格并添加水印，我们可以使用Apache POI和iText库。下面是一个示例代码：

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Date;

import com.itextpdf.text.Document;
import com.itextpdf.text.Element;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfWriter;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class TableWithWatermark {
    public static void main(String[] args) {
        String fileName = "table_with_watermark.pdf";
        String watermark = "Confidential";
        int numRows = 10;
        int numCols = 5;

        // Create a new workbook and sheet
        Workbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet("Sheet1");

        // Generate random data and fill the sheet
        for (int i = 0; i < numRows; i++) {
            Row row = sheet.createRow(i);
            for (int j = 0; j < numCols; j++) {
                Cell cell = row.createCell(j);
                cell.setCellValue(Math.random() * 100);
            }
        }

        try {
            // Create a new PDF document
            Document document = new Document();
            PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(fileName));
            document.open();
            PdfContentByte cb = writer.getDirectContent();

            // Add the watermark to the PDF document
            Phrase watermarkPhrase = new Phrase(watermark);
            float fontSize = 60;
            float x = (document.getPageSize().getWidth() - watermarkPhrase.getWidthPoint()) / 2;
            float y = (document.getPageSize().getHeight() - watermarkPhrase.getHeightPoint()) / 2;
            cb.beginText();
            cb.setFontAndSize(watermarkPhrase.getFont(), fontSize);
            cb.showTextAligned(Element.ALIGN_CENTER, watermark, x, y, 45);
            cb.endText();

            // Create a new table and add it to the PDF document
            PdfPTable table = new PdfPTable(numCols);
            for (int i = 0; i < numRows; i++) {
                Row row = sheet.getRow(i);
                for (int j = 0; j < numCols; j++) {
                    Cell cell = row.getCell(j);
                    PdfPCell pdfCell = new PdfPCell(new Phrase(cell.toString()));
                    table.addCell(pdfCell);
                }
            }
            document.add(table);
            document.close();
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

在这个示例中，我们首先使用Apache POI生成一个Excel表格，然后使用iText将其写入PDF文件。我们还添加了一个水印，该水印位于PDF页面的中心。最后，我们将Excel表格中的数据添加到PDF表格中