如何在Java中将两个PDF文件合并为一个？

Question

我想使用PDFBox 将许多 PDF 文件合并为一个，这就是我所做的：

PDDocument document = new PDDocument();
for (String pdfFile: pdfFiles) {
    PDDocument part = PDDocument.load(pdfFile);
    List<PDPage> list = part.getDocumentCatalog().getAllPages();
    for (PDPage page: list) {
        document.addPage(page);
    }
    part.close();
}
document.save("merged.pdf");
document.close();

其中pdfFiles 是一个包含所有PDF 文件的ArrayList<String>。

当我运行上述内容时，我总是得到：

org.apache.pdfbox.exceptions.COSVisitorException: Bad file descriptor

我做错了吗？还有其他方法吗？

Answer 1

快速的 Google 搜索返回了这个错误："Bad file descriptor while saving a document w. imported PDFs"。

您似乎需要将要合并的 PDF 保持打开状态，直到您保存并关闭合并的 PDF。

Answer 2

为什么不用pdfbox的PDFMergerUtility呢？

PDFMergerUtility ut = new PDFMergerUtility();
ut.addSource(...);
ut.addSource(...);
ut.addSource(...);
ut.setDestinationFileName(...);
ut.mergeDocuments();

Answer 3

package article14;

import java.io.File;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.util.PDFMergerUtility;

public class Pdf
{
    public static void main(String args[])
    {
        new Pdf().createNew();
        new Pdf().combine();
        }

    public void combine()
    {
        try
        {
        PDFMergerUtility mergePdf = new PDFMergerUtility();
        String folder ="pdf";
        File _folder = new File(folder);
        File[] filesInFolder;
        filesInFolder = _folder.listFiles();
        for (File string : filesInFolder)
        {
            mergePdf.addSource(string);    
        }
    mergePdf.setDestinationFileName("Combined.pdf");
    mergePdf.mergeDocuments();
        }
        catch(Exception e)
        {

        }  
    }

public void createNew()
{
    PDDocument document = null;
    try
    {
        String filename="test.pdf";
        document=new PDDocument();
        PDPage blankPage = new PDPage();
        document.addPage( blankPage );
        document.save( filename );
    }
    catch(Exception e)
    {

    }
}

}

Answer 4

如果您想合并两个文件，其中一个文件覆盖另一个文件（例如：文档 A 是一个模板，而文档 B 有您要放置在模板上的文本），这可行：

创建“doc”后，您想在其上编写模板（templateFile）-

   PDDocument watermarkDoc = PDDocument.load(getServletContext()
                .getRealPath(templateFile));
   Overlay overlay = new Overlay();

   overlay.overlay(watermarkDoc, doc);

Answer 5

这是一个即用型代码，将四个 pdf 文件与来自 http://central.maven.org/maven2/com/itextpdf/itextpdf/5.5.0/itextpdf-5.5.0.jar 的 itext.jar 合并，更多内容请参见 http://tutorialspointexamples.com/

import com.itextpdf.text.Document;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfImportedPage;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfWriter;

/**
 * This class is used to merge two or more 
 * existing pdf file using iText jar.
 */
public class PDFMerger {

static void mergePdfFiles(List<InputStream> inputPdfList,
        OutputStream outputStream) throws Exception{
    //Create document and pdfReader objects.
    Document document = new Document();
    List<PdfReader> readers = 
            new ArrayList<PdfReader>();
    int totalPages = 0;

    //Create pdf Iterator object using inputPdfList.
    Iterator<InputStream> pdfIterator = 
            inputPdfList.iterator();

    // Create reader list for the input pdf files.
    while (pdfIterator.hasNext()) {
            InputStream pdf = pdfIterator.next();
            PdfReader pdfReader = new PdfReader(pdf);
            readers.add(pdfReader);
            totalPages = totalPages + pdfReader.getNumberOfPages();
    }

    // Create writer for the outputStream
    PdfWriter writer = PdfWriter.getInstance(document, outputStream);

    //Open document.
    document.open();

    //Contain the pdf data.
    PdfContentByte pageContentByte = writer.getDirectContent();

    PdfImportedPage pdfImportedPage;
    int currentPdfReaderPage = 1;
    Iterator<PdfReader> iteratorPDFReader = readers.iterator();

    // Iterate and process the reader list.
    while (iteratorPDFReader.hasNext()) {
            PdfReader pdfReader = iteratorPDFReader.next();
            //Create page and add content.
            while (currentPdfReaderPage <= pdfReader.getNumberOfPages()) {
                  document.newPage();
                  pdfImportedPage = writer.getImportedPage(
                          pdfReader,currentPdfReaderPage);
                  pageContentByte.addTemplate(pdfImportedPage, 0, 0);
                  currentPdfReaderPage++;
            }
            currentPdfReaderPage = 1;
    }

    //Close document and outputStream.
    outputStream.flush();
    document.close();
    outputStream.close();

    System.out.println("Pdf files merged successfully.");
}

public static void main(String args[]){
    try {
        //Prepare input pdf file list as list of input stream.
        List<InputStream> inputPdfList = new ArrayList<InputStream>();
        inputPdfList.add(new FileInputStream("..\\pdf\\pdf_1.pdf"));
        inputPdfList.add(new FileInputStream("..\\pdf\\pdf_2.pdf"));
        inputPdfList.add(new FileInputStream("..\\pdf\\pdf_3.pdf"));
        inputPdfList.add(new FileInputStream("..\\pdf\\pdf_4.pdf"));


        //Prepare output stream for merged pdf file.
        OutputStream outputStream = 
                new FileOutputStream("..\\pdf\\MergeFile_1234.pdf");

        //call method to merge pdf files.
        mergePdfFiles(inputPdfList, outputStream);     
    } catch (Exception e) {
        e.printStackTrace();
    }
    }
}

Answer 6

使用 iText（以字节为单位的现有 PDF）

    public static byte[] mergePDF(List<byte[]> pdfFilesAsByteArray) throws DocumentException, IOException {

    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    Document document = null;
    PdfCopy writer = null;

    for (byte[] pdfByteArray : pdfFilesAsByteArray) {

        try {
            PdfReader reader = new PdfReader(pdfByteArray);
            int numberOfPages = reader.getNumberOfPages();

            if (document == null) {
                document = new Document(reader.getPageSizeWithRotation(1));
                writer = new PdfCopy(document, outStream); // new
                document.open();
            }
            PdfImportedPage page;
            for (int i = 0; i < numberOfPages;) {
                ++i;
                page = writer.getImportedPage(reader, i);
                writer.addPage(page);
            }
        }

        catch (Exception e) {
            e.printStackTrace();
        }

    }

    document.close();
    outStream.close();
    return outStream.toByteArray();

}

Answer 7

使用org.apache.pdfbox的多个pdf合并方法：

public void mergePDFFiles(List<File> files,
                          String mergedFileName) {
    try {
        PDFMergerUtility pdfmerger = new PDFMergerUtility();
        for (File file : files) {
            PDDocument document = PDDocument.load(file);
            pdfmerger.setDestinationFileName(mergedFileName);
            pdfmerger.addSource(file);
            pdfmerger.mergeDocuments(MemoryUsageSetting.setupTempFileOnly());
            document.close();
        }
    } catch (IOException e) {
        logger.error("Error to merge files. Error: " + e.getMessage());
    }
}

在主程序中，使用文件列表和目标文件名调用 mergePDFFiles 方法。

        String mergedFileName = "Merged.pdf";
        mergePDFFiles(files, mergedFileName);

调用mergePDFFiles后，加载合并文件

        File mergedFile = new File(mergedFileName);