Apache PDFBox Extract Embedded File from PDF Document

Previously we saw how to add an embedded file to a pdf document. This tutorial demonstrates how to extract an embedded file from a PDF document.

Maven Dependencies

We use Apache Maven to manage our project dependencies. Make sure the following dependencies reside on the class-path.

<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>2.0.8</version>
</dependency>

Apache PDFBox Extract Embedded File from PDF Document

The following example extracts all embedded files from a PDF document.

package com.memorynotfound.pdf.pdfbox;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDDocumentNameDictionary;
import org.apache.pdfbox.pdmodel.PDEmbeddedFilesNameTreeNode;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDNameTreeNode;
import org.apache.pdfbox.pdmodel.common.filespecification.PDComplexFileSpecification;
import org.apache.pdfbox.pdmodel.common.filespecification.PDEmbeddedFile;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotation;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationFileAttachment;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;
import java.util.Map;

public class ExtractEmbeddedFiles {

    private static final String OUTPUT_DIR = "/tmp";
    
    public static void main(String[] args) throws Exception{

        try (final PDDocument document = PDDocument.load(new File("/tmp/embedded-file.pdf"))){
            PDDocumentNameDictionary namesDictionary = new PDDocumentNameDictionary( document.getDocumentCatalog());
            PDEmbeddedFilesNameTreeNode efTree = namesDictionary.getEmbeddedFiles();
            if (efTree != null) {
                Map<String, PDComplexFileSpecification> names = efTree.getNames();
                if (names != null) {
                    extractFiles(names);
                } else {
                    List<PDNameTreeNode<PDComplexFileSpecification>> kids = efTree.getKids();
                    for (PDNameTreeNode<PDComplexFileSpecification> node : kids) {
                        names = node.getNames();
                        extractFiles(names);
                    }
                }
            }

            // extract files from annotations
            for (PDPage page : document.getPages()) {
                for (PDAnnotation annotation : page.getAnnotations()) {
                    if (annotation instanceof PDAnnotationFileAttachment) {
                        PDAnnotationFileAttachment annotationFileAttachment = (PDAnnotationFileAttachment) annotation;
                        PDComplexFileSpecification fileSpec = (PDComplexFileSpecification) annotationFileAttachment.getFile();
                        PDEmbeddedFile embeddedFile = getEmbeddedFile(fileSpec);
                        extractFile(fileSpec.getFilename(), embeddedFile);
                    }
                }
            }
        } catch (IOException e){
            System.err.println("Exception while trying to read pdf document - " + e);
        }
    }

    private static void extractFiles(Map<String, PDComplexFileSpecification> names) throws IOException {
        for (Map.Entry<String, PDComplexFileSpecification> entry : names.entrySet()) {
            PDComplexFileSpecification fileSpec = entry.getValue();
            String filename = fileSpec.getFile();
            PDEmbeddedFile embeddedFile = getEmbeddedFile(fileSpec);
            extractFile(filename, embeddedFile);
        }
    }

    private static void extractFile(String filename, PDEmbeddedFile embeddedFile) throws IOException {
        String embeddedFilename = OUTPUT_DIR + filename;
        File file = new File(embeddedFilename);
        System.out.println("Writing " + embeddedFilename);
        try (FileOutputStream fos = new FileOutputStream(file)) {
            fos.write(embeddedFile.toByteArray());
        }
    }

    private static PDEmbeddedFile getEmbeddedFile(PDComplexFileSpecification fileSpec) {
        PDEmbeddedFile embeddedFile = null;
        if (fileSpec != null) {
            embeddedFile = fileSpec.getEmbeddedFileUnicode();
            if (embeddedFile == null) {
                embeddedFile = fileSpec.getEmbeddedFileDos();
            }
            if (embeddedFile == null) {
                embeddedFile = fileSpec.getEmbeddedFileMac();
            }
            if (embeddedFile == null) {
                embeddedFile = fileSpec.getEmbeddedFileUnix();
            }
            if (embeddedFile == null) {
                embeddedFile = fileSpec.getEmbeddedFile();
            }
        }
        return embeddedFile;
    }

}

Output

When we run the application. The embedded file is extracted from the PDF document.

References

• Apache PdfBox Official Website
• Apache PdfBox API Javadoc
• PDDocument JavaDoc
• PDEmbeddedFile JavaDoc
• PDComplexFileSpecification JavaDoc
• PDEmbeddedFilesNameTreeNode JavaDoc

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