java - servlet 创建的 Pdf 文件未正确加载

Question

friend 们，我已经实现了一个jsp表单，它接受pdf文件的标题、描述和内容等输入。当提交 jsp 表单时，将在名为“pdfGenServlet.java”的 servlet 的帮助下使用 itext 创建 pdf。

我的jsp表单是

<form action="pdfGenServlet1" method="get" enctype="application/x-www-form-urlencoded">
                <!-- input notes title-->
                <div class="form-group">
                    <div class="input-group">
                        <input type="text" class="form-control" placeholder="Title of the notes" name="title">
                    </div>
                </div>
                <!-- input notes description-->
                <div class="form-group">
                    <div class="input-group">
                        <input type="text" class="form-control" placeholder="Enter short description" name="description">
                    </div>
                </div>

                <div class="form-group">
                  <textarea name="content" id="myEditor"></textarea>

                 <div id="button-panel" class="panel panel-default">
                      <p>
                          <button type="submit" class="btn btn-primary "><span class="glyphicon glyphicon-plus"></span><strong> Create Note</strong></button>
                          <button class="btn btn-primary" type="reset"><strong>Reset</strong></button>
                      </p><!-- buttons -->
                 </div><!-- panel Button -->

                </div>

            </form> 

servlet“pdfGenServlet.java”

//imports for itext
import java.io.FileOutputStream;
import java.io.StringReader;
import com.itextpdf.text.BaseColor;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Font;
import com.itextpdf.text.Font.FontFamily;
import com.itextpdf.text.Document;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.html.simpleparser.HTMLWorker; // deprecated
import com.itextpdf.text.pdf.PdfWriter;

//servlet imports
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//File handling and java util
import java.io.ByteArrayOutputStream;
import java.io.OutputStream;
import java.util.Date;


@WebServlet("/pdfGenServlet1")
public class pdfGenServlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    try {

        //Font for using with itext
        Font bfBold18 = new Font(FontFamily.TIMES_ROMAN, 18, Font.BOLD, new BaseColor(0, 0, 0)); 
        Font bfBold12 = new Font(FontFamily.TIMES_ROMAN, 12, Font.BOLD, new BaseColor(0, 0, 0)); 

        String title = request.getParameter("title");
        String description = request.getParameter("description");
        String notes_content = request.getParameter("content");
        Date date = new Date();

        Document document = new Document(PageSize.A4);
        PdfWriter.getInstance(document, new FileOutputStream("C://BEProject//PreparedNotes//testpdf1.pdf"));
        HTMLWorker htmlWorker = new HTMLWorker(document);
        document.open();

        document.addAuthor("Real Gagnon");
        document.addCreator("Real's HowTo");
        document.addSubject("Thanks for your support");
        document.addCreationDate();
        document.addTitle("Please read this");

        //
        document.addCreationDate();
        document.add(new Paragraph("TITLE: ", bfBold18));
        document.add(new Paragraph(title,bfBold12));
        document.add(new Paragraph("\n"));
        document.add(new Paragraph(String.format("Created on: " + date.toString())));
        document.add(new Paragraph("DESCRIPTION: ", bfBold18));
        document.add(new Paragraph(description,bfBold12));
        document.add(new Paragraph("\n"));

        htmlWorker.parse(new StringReader(notes_content));
        // step 5
        document.close();

        response.setHeader("Content-disposition", "attachment; filename= testpdf1.pdf");

        response.setContentType("application/pdf");

    } catch (DocumentException e) {

        e.printStackTrace();
    }




}

} 请自己尝试一下代码。您会看到自动创建的 pdf 文件下载，但打开时显示正在加载，但不会像这样加载

当在目录中创建的相同文件显示在 pdfGenServlet 的“C://BEProject//PreparedNotes//testpdf1.pdf”中时。 当手动打开 testpdf1.pdf 时，它可以正常打开。 请帮忙

Answer 1

您在本地磁盘上创建 PDF，并设置一些发送到浏览器的标题。您不会向浏览器发送任何字节，因此您不应期望在浏览器中看到任何内容。这与您描述的行为一致。

在另一个答案中，有人告诉您将 PDF 字节写入 HttpServletResponse。最简单的方法是按照 the book I wrote about iText 中的示例进行操作。 ，更具体地说，Hello示例:

protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
    response.setContentType("application/pdf");
    try {
        // step 1
        Document document = new Document();
        // step 2
        PdfWriter.getInstance(document, response.getOutputStream());
        // step 3
        document.open();
        // step 4
        document.add(new Paragraph("Hello World"));
        document.add(new Paragraph(new Date().toString()));
        // step 5
        document.close();
    } catch (DocumentException de) {
        throw new IOException(de.getMessage());
    }
}

你可以试试这个例子here .

在理想的情况下，这适用于所有浏览器。不幸的是，并非所有浏览器都是一样的，因此您可能希望按照PdfServlet以更具防御性的方式进行编码。示例:

protected void service(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
    try {
        // Get the text that will be added to the PDF
        String text = request.getParameter("text");
        if (text == null || text.trim().length() == 0) {
             text = "You didn't enter any text.";
        }
        // step 1
        Document document = new Document();
        // step 2
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        PdfWriter.getInstance(document, baos);
        // step 3
        document.open();
        // step 4
        document.add(new Paragraph(String.format(
            "You have submitted the following text using the %s method:",
            request.getMethod())));
        document.add(new Paragraph(text));
        // step 5
        document.close();

        // setting some response headers
        response.setHeader("Expires", "0");
        response.setHeader("Cache-Control",
            "must-revalidate, post-check=0, pre-check=0");
        response.setHeader("Pragma", "public");
        // setting the content type
        response.setContentType("application/pdf");
        // the contentlength
        response.setContentLength(baos.size());
        // write ByteArrayOutputStream to the ServletOutputStream
        OutputStream os = response.getOutputStream();
        baos.writeTo(os);
        os.flush();
        os.close();
        // if you also want to write these bytes to a file, add:
        OutputStream fos = new FileOutputStream(pathToFile);
        baos.writeTo(fos);
        fos.flush();
        fos.close();
    }
    catch(DocumentException e) {
        throw new IOException(e.getMessage());
    }
}

您可以尝试这个 servlet here 。如您所见，我们现在首先在内存中创建文件。我们这样做是为了设置内容长度的 header (某些浏览器需要这样做)。我还设置了一些可能不必要的其他 header ，但这些 header 是多年来根据数千名 iText 用户的反馈添加到我的示例中的。