PDFBox Working with Attachments

A PDF document can contain references to an external file via the file system or a URL to a remote location. It is also possible to embed a binary file into a PDF document.

An Apache PDFBox provides following classes that can be used in referencing a file.

Class	Discription
PDSimpleFileSpecification	It is a simple string reference to a file. The PDSimpleFileSpecification class does not allow for any parameters to be set.
PDComplexFileSpecification	It is more feature rich class and allows for advanced settings for reference to a file.

In PDFBox, it is also possible to embed a file directly into a PDF document. This can be performed by using the EmbeddedFile attribute instead of setting the file attribute of the PDComplexFileSpecification class.

Embed File into PDF Document

PDF documents can contain file attachments. The file attachments are accessed from the Document->File Attachments menu. PDFBox allows us to add attachments in a PDF document and also extracted that attachments from PDF documents. In PDFBox, attachments are part of the named tree that is attached to the document catalogue.

Following are the step by step procedure to add attachments to PDF file.

Load Existing Document

We can load the existing PDF document by using the static load () method. This method accepts a file object as a parameter. We can also invoke it using the class name PDDocument of the PDFBox.

File file = new File("PATH"); 
PDDocument doc = PDDocument.load(file); 

Instantiate PDDocumentNameDictionary

In this, attachments are stored as a part of the "names" dictionary in the document catalogue.

PDDocumentNameDictionary names = new DdocumentNameDictionary (doc.getDocumentCatalog());

Retrieve Existing Attachments and Add New Attachments

PDEmbeddedFilesNameTreeNode efTree = names.getEmbeddedFiles();
 Map existedNames = efTree.getNames();

Create the file specification, which holds the embedded file

PDComplexFileSpecification fs = new PDComplexFileSpecification();
        fs.setFile( "Test.txt" );
        InputStream is = ...;
        PDEmbeddedFile ef = new PDEmbeddedFile(doc, is );

Example-

import org.apache.pdfbox.pdmodel.*;
import org.apache.pdfbox.pdmodel.common.filespecification.PDComplexFileSpecification;
import org.apache.pdfbox.pdmodel.common.filespecification.PDEmbeddedFile;
import org.apache.pdfbox.pdmodel.font.PDType1Font;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.util.*;

public class AddingAttachments {
	public static void main(String[] args)throws IOException {
				
		try (final PDDocument doc = new PDDocument()){

            PDPage page = new PDPage();
doc.addPage(page);

          PDPageContentStream contentStream = new PDPageContentStream(doc, page);

contentStream.beginText();
contentStream.setFont(PDType1Font.HELVETICA, 12);
contentStream.newLineAtOffset(100, 700);
contentStream.showText("Go to Document -> File Attachments to View Embedded Files");
contentStream.endText();
contentStream.close();

// embedded files are stored in a named tree
            PDEmbeddedFilesNameTreeNode efTree = new PDEmbeddedFilesNameTreeNode();

// first create the file specification, which holds the embedded file
            PDComplexFileSpecification fs = new PDComplexFileSpecification();
fs.setFile("example-document.txt");

// create a dummy file stream, this would probably normally be a FileInputStream
byte[] data = "This is the contents of the embedded file".getBytes("ISO-8859-1");
            ByteArrayInputStream fakeFile = new ByteArrayInputStream(data);

// now lets some of the optional parameters
            PDEmbeddedFile ef = new PDEmbeddedFile(doc, fakeFile);
ef.setSubtype("text/plain");
ef.setSize(data.length);
ef.setCreationDate(Calendar.getInstance());
fs.setEmbeddedFile(ef);

// create a new tree node and add the embedded file 
            PDEmbeddedFilesNameTreeNode treeNode = new PDEmbeddedFilesNameTreeNode();
treeNode.setNames(Collections.singletonMap("My first attachment",  fs));

// add the new node as kid to the root node
            List<PDEmbeddedFilesNameTreeNode>kids = new ArrayList<PDEmbeddedFilesNameTreeNode>();
kids.add(treeNode);
efTree.setKids(kids);

// add the tree to the document catalog
            PDDocumentNameDictionary names = new PDDocumentNameDictionary(doc.getDocumentCatalog());
names.setEmbeddedFiles(efTree);
doc.getDocumentCatalog().setNames(names);

doc.save(new File("/eclipse-workspace/embedded-file.pdf"));
            System.out.println("Embaded PDF file is created");
        } catch (IOException e){
       System.err.println("Exception while trying to create pdf document - " + e);
      }
   }
}

Output: