使用iText创建PDF

Question

null

// read in template pdf
InputStream templateStream = getServletContext().getResourceAsStream(labelsTemplate);
PdfReader reader = new PdfReader(templateStream);

// create a table in a new document
Document document = new Document();
PdfCopy copy = new PdfCopy(document, os);
document.open();

PdfPTable table = new PdfPTable(2);
PdfPCell cell;
cell = new PdfPCell(new Phrase("row 1; cell 1"));
table.addCell(cell);
cell = new PdfPCell(new Phrase("row 1; cell 2"));
table.addCell(cell);
document.add(table);

有人能解释一下，当我使用PdfReader阅读模板后，我如何制作模板的副本吗？有没有办法把表格写到模板副本上，而不是一个新文档上？

为了将来的参考，我做了以下工作：

response.setContentType("application/pdf");
response.setHeader("Content-Disposition", "inline;filename=\"scheduler-labels.pdf\"");
ServletOutputStream os = response.getOutputStream();

// read in template pdf
InputStream templateStream = getServletContext().getResourceAsStream(labelsTemplate);
PdfReader reader = new PdfReader(templateStream);

// make new pdf document to draw table and output to memory
Document document = new Document(reader.getPageSize(1));
ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
PdfWriter.getInstance(document, baos);

// write table
document.open();
PdfPTable table = new PdfPTable(2);
table.setWidthPercentage(110);
PdfPCell cell;
cell = new PdfPCell(new Phrase("row 1; cell 1"));
table.addCell(cell);
cell = new PdfPCell(new Phrase("row 1; cell 2"));
table.addCell(cell);
cell = new PdfPCell(new Phrase("row 2; cell 1"));
table.addCell(cell);
cell = new PdfPCell(new Phrase("row 2; cell 2"));
table.addCell(cell);
document.add(table);
document.close();

// read in newly generated table pdf
PdfReader tableReader = new PdfReader(baos.toByteArray());
ByteArrayOutputStream baosCombined = new ByteArrayOutputStream();
PdfStamper stamper = new PdfStamper(tableReader, baosCombined);

// get a page from the template pdf
PdfImportedPage page = stamper.getImportedPage(reader, 1);

// add to background of table pdf
PdfContentByte background;
background = stamper.getUnderContent(1);
background.addTemplate(page, 0, 0);

stamper.close();
tableReader.close();
reader.close();

// write to servlet output
baosCombined.writeTo(os);
os.flush();
os.close();

Answer 1

因为研究我评论中提到的样本正是[Tuan]所需要的，所以我将其表述为一个答案：

iText in Action-2 Edition第6章的示例Stationery.java基本上展示了如何将给定PDF的内容用作新PDF的背景（类似于文具），同时用新内容填充其前台。

中央代码如下：

public class Stationery extends PdfPageEventHelper
{
    [...]

    public void createPdf(String filename) throws Exception
    {
        // step 1
        Document document = new Document(PageSize.A4, 36, 36, 72, 36);
        // step 2
        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(filename));
        useStationary(writer);
        // step 3
        document.open();
        // step 4
        [... add content to PDF ...]
        // step 5
        document.close();
    }

    [...]

    public void useStationary(PdfWriter writer) throws IOException
    {
        writer.setPageEvent(this);
        PdfReader reader = new PdfReader(STATIONERY);
        page = writer.getImportedPage(reader, 1);
    }

    public void onEndPage(PdfWriter writer, Document document)
    {
        writer.getDirectContentUnder().addTemplate(page, 0, 0);
    }

    [...]
}