根据数据生成PDF并且下载

1.先创建文件夹，保存要生成的pdf

2.获得要输出的pdf的文件流

3.保存文件。

直接上代码：

    public void downloadDispensingDetail(@PathVariable("id") Integer id, HttpSession session,
            HttpServletResponse response, HttpServletRequest request) throws IOException {
        if (null == id) {
            return;
        }
        
        User loginUser = LoginUserHelper.getCurrentUser(session);
        if (loginUser == null) {
            return;
        }

　　　　　//根据自己的项目封装的model
        PrintDispensingDetailPageModel model = dispensingService.getPrintDispensingDetail(id);
        if (null == model) {
            return;
        }

        //获取到tomcat路径
        String path = request.getSession().getServletContext().getRealPath("");
        String realPath = new File(path).getParentFile().getParent();
        //新生成的文件地址
//        String filename = realPath + "/发药记录-" + model.getId() + ".pdf";
        String filename = realPath + File.separator + "发药记录-" + model.getId()
                + ".pdf";
        File oldfile = new File(filename);
        // 若文件已存在，直接返回，不重复生成
        if (oldfile.exists() && oldfile.isFile()) {
            System.out.println("file  is  have ");
        }else{
                 //生成pdf文件
                Document document = new Document(PageSize.A4, 50, 50, 50, 50);
                PdfWriter writer = null;
                try {
                    PdfWriter.getInstance(document, new FileOutputStream(filename));
                    document.open();
        
                    FontFactoryImp fontFactory = new FontFactoryImp();
                    fontFactory.registerDirectories();
                    Font titleFont = fontFactory.getFont("微软雅黑", BaseFont.IDENTITY_H, BaseFont.EMBEDDED, 20, Font.BOLD, null);
        
                    // 标题
                    Paragraph title = new Paragraph("发药记录", titleFont);
                    title.setAlignment(Element.ALIGN_CENTER);
                    title.setSpacingAfter(20f);
                    document.add(title);
        
                    Font font = fontFactory.getFont("微软雅黑", BaseFont.IDENTITY_H, BaseFont.EMBEDDED, 12, Font.UNDEFINED, null);
        
                    PdfPTable table = new PdfPTable(4);
        
                    table.addCell(new Paragraph("受试者编号", font));
                    table.addCell(new Paragraph(model.getPatientNum(), font));
                    table.addCell(new Paragraph("受试者姓名", font));
                    table.addCell(new Paragraph(model.getPatientName(), font));
        
                    table.addCell(new Paragraph("发药时间", font));
                    table.addCell(new Paragraph(model.getDispensingTime(), font));
                    table.addCell(new Paragraph("发药数目", font));
                    table.addCell(new Paragraph("" + model.getDrugRandomIds().size(), font));
        
                    PdfPCell cell;
                    cell = new PdfPCell(new Paragraph("医院编号", font));
                    cell.setColspan(2);
                    table.addCell(cell);
                    cell = new PdfPCell(new Paragraph(loginUser.getHospital().getHospitaNumber(), font));
                    cell.setColspan(2);
                    table.addCell(cell);
        
                    cell = new PdfPCell(new Paragraph("医院名称", font));
                    cell.setColspan(2);
                    table.addCell(cell);
                    cell = new PdfPCell(new Paragraph(loginUser.getHospital().getName(), font));
                    cell.setColspan(2);
                    table.addCell(cell);
        
                    cell = new PdfPCell(new Paragraph("药物编号", font));
                    cell.setColspan(4);
                    table.addCell(cell);
        
                    for (int i = 0; i < model.getDrugRandomIds().size(); i++) {
                        table.addCell(new Paragraph(model.getDrugRandomIds().get(i), font));
                    }
                    // 补齐最后一行
                    if (model.getDrugRandomIds().size() % 4 != 0) {
                        for (int j = model.getDrugRandomIds().size() % 4; j < 4; j++) {
                            table.addCell("");
                        }
                    }
                    document.add(table);
                } catch (Exception e) {
                    e.printStackTrace();
                    System.out.println("pdf crate  fail");
                } finally {
                    document.close();
                    if (null != writer) {
                        writer.close();
                    }
                }
            System.out.println("pdf crate  success:"+filename);
        }
        
        // 下面是下载
        response.setContentType("text/html; charset=UTF-8"); // 设置编码字符
        response.setContentType("application/x-msdownload"); // 设置内容类型为下载类型
        response.setHeader("Content-Disposition",
                "attachment; filename=" + new String(("发药记录-" + model.getId() + ".pdf").getBytes(), "iso8859-1"));
//        response.setHeader("Content-Disposition", "attachment;filename=yltsqb.pdf");
        
        try {
            ServletOutputStream out = response.getOutputStream();
            File file = new File(realPath +  File.separator+"发药记录-" + model.getId() + ".pdf"); // 创建文件
            FileInputStream fis = new FileInputStream(realPath +  File.separator+"发药记录-" + model.getId() + ".pdf"); // 创建文件字节输入流  来源文件
            BufferedInputStream buff = new BufferedInputStream(fis); // 创建文件缓冲输入流
            byte[] b = new byte[2048]; // 设置每次读取大小
            long l = 0; // 用于判断是否等同于文件的长度，即文件下载大小
            while (l < file.length()) { // 循环读取文件
                int j = buff.read(b, 0, 2048); // 使用缓冲流读取数据,返回缓冲区长度
                l += j;
                out.write(b, 0, j);// 将缓存写入客户端
            }
            buff.close();
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("dowland success");
    }

注意：要根据自己的项目来封装model.