Java 合并PDF文件

PDFMergerUtility类用于将多个PDF文档合并为一个PDF文档。PDFMergerUtility类将接受多个PDF文件进行合并，并将结果保存为一个新文档。要使用java合并PDF文件，需要安装Apache库。使用java合并PDF文件可能有不同的方法。

定义：使用Java合并PDF文件

示例

输入 − PDF1 = Alice.pdf，PDF2 = Bob.pdf

输出 − newMerged.pdf // pdf1和pdf2合并后的PDF文件

程序代码

// Merging two pdf documents here 

import org.apache.pdfbox.multipdf.PDFMergerUtility;
import org.apache.pdfbox.pdmodel.PDDocument;
import java.io.File;
import java.io.IOException;

public class GFG {
   public static void main(String[] args)
      throws IOException
      {

      // loading all the pdf files we wish to merge

      File file1 = new File( "/Users/abhilasha/Desktop/Merging Pdfs/file1.pdf");
      File file2 = new File("/Users/abhilasha/Desktop/Merging Pdfs/file2.pdf");

      // Instantiating PDFMergerUtility class
      PDFMergerUtility obj = new PDFMergerUtility();

      // Setting the destination file path 
      obj.setDestinationFileName("/Users/abhilasha/Desktop/Merging Pdfs/newMerged.pdf");

      // Add all source files, to be merged
      obj.addSource(file1);
      obj.addSource(file2);

      // Merging documents
      obj.mergeDocuments();

      System.out.println( "PDF Documents merged to a single file");
   }
}

步骤

使用apache库，我们必须按照以下步骤合并多个PDF文档：

步骤1 - 作为第一步，我们必须安装PDFMergerUtility类。
步骤2 - 对于下一步，使用setDestinationFileName()方法来设置目标文件。
步骤3 - 现在，使用addSource()方法设置源文件。
步骤4 - 对于最后一步，我们使用PDFMergerUtility类的mergeDocuments()方法来合并PDF文档。

输出

代码执行前 –

Java 合并PDF文件

代码执行后 –

Java 合并PDF文件

方法

方法1 - 使用Java中的Itext合并两个PDF文件

方法2 - 使用Java中的InputStream合并多个PDF文件

方法1：使用Itext在Java中合并两个PDF文件

代码

import java.io.FileInputStream;import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
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.
* @author w3spoint
*/public class PDFMergeExample {
   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("D:\TestFile1.pdf"));
         inputPdfList.add(new FileInputStream("D:\TestFile2.pdf"));

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

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

输出

Pdf file merged successfully.

方法2：使用输入流合并两个PDF文件

要通过使用输入流合并PDF文件，我们必须使用另一个mergeFiles（）方法，通过传递一个输入流数组。

程序代码

import com.spire.pdf.PdfDocument
import com.spire.pdf.PdfDocumentBase;
import java.io.*;
public class MergePdfsUsingInputStreams {
   public static void main(String []args) throws FileNotFoundException {
      //Load the PDF files into FileInputStream objects
      FileInputStream stream1 = new FileInputStream("File1.pdf");
      FileInputStream stream2 = new FileInputStream("File2.pdf");
      FileInputStream stream3 = new FileInputStream("File3.pdf");
      //Create a InputStream array for the FileInputStream objects
      InputStream[] streams = new FileInputStream[]{stream1, stream2, stream3}; //Merge the PDF files
      PdfDocumentBase pdf = PdfDocument.mergeFiles(streams);
      //Create a OutputStream for the merged PDF
      OutputStream outputStream = new FileOutputStream("Merge.pdf");
      //Save the merged PDF file pdf.save(outputStream);
   }
}

输出