java - PDFWriter 中的 ByteArrayOutputStream 大小为零？

Question

在过去的 1 小时里我一直在伤脑筋，我无法解决这个问题...我知道用 java 编写 PDF 很容易，但我的输出流大小为零，...这是我的代码..

 Document document = new Document();
      try
    {
        ByteArrayOutputStream dsf = new ByteArrayOutputStream();
        PdfWriter writer = PdfWriter.getInstance(document, dsf);
        document.open();
        document.add(new Paragraph("Some content here"));

        // Set attributes here
        document.addAuthor("Lokesh Gupta");
        document.addCreationDate();
        document.addCreator("HowToDoInJava.com");
        document.addTitle("Set Attribute Example");
        document.addSubject("An example to show how attributes can be added to pdf files.");
        if (frontPageMap != null && !frontPageMap.isEmpty()) {

            PdfPTable table = new PdfPTable(frontPageMap.size()); // creating
                                                                    // columns.
            table.setWidthPercentage(100); // Width 100%
            table.setSpacingBefore(10f); // Space before table
            table.setSpacingAfter(10f); // Space after table

            for (Map.Entry<String, Object> entry : frontPageMap.entrySet()) {
                PdfPCell tempCell = new PdfPCell(new Paragraph(entry.getKey()));
                tempCell.setBorderColor(BaseColor.BLUE);
                tempCell.setPaddingLeft(10);
                tempCell.setHorizontalAlignment(Element.ALIGN_CENTER);
                tempCell.setVerticalAlignment(Element.ALIGN_MIDDLE);
                table.addCell(tempCell);
            }
            document.add(table);

        }
        System.out.println("Size Of Byte Array is "+dsf.size());
        ByteArrayInputStream bInput = new ByteArrayInputStream(dsf.toByteArray());
        file = new DefaultStreamedContent(bInput, "pdf", fileName);
        document.close();
        writer.close();

NOTE:I am able to print map key values also but When i download PDF the size is zero.

Answer 1

也许您应该在尝试之前完成 PDF 创建(使用 document.close() 和 writer.close())访问内容:

    //Finish writing the PDF
    document.close();
    writer.close();
    //now check what's been written:
    System.out.println("Size Of Byte Array is "+dsf.size());
    ByteArrayInputStream bInput = new ByteArrayInputStream(dsf.toByteArray());
    file = new DefaultStreamedContent(bInput, "pdf", fileName);