PDFDocument.java

/*
Author: Scott Field
Name: PDFDocument
Date: 09/21/2023
Version: 1.0
Purpose:
A class to storing the methods for loading a PDF from a File
or from a web URL
*/
import java.net.*;

import org.apache.commons.io.output.ByteArrayOutputStream;

import java.io.File;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public abstract class PDFDocument {
    // Declare pdfFile as an instance variable
    protected File pdfFile;
    protected String pdfPath;
    protected Boolean isValid = false;

    //Empty Constructor
    public PDFDocument() {
        // Initialize pdfFile and pdfPath in the constructor
        pdfFile = null;
        pdfPath = null;
        isValid = false;
    }

    //Local File Constructor
    public PDFDocument(File newFile){
        isValid = this.loadPDF(newFile);
    }

    //URL Constructor
    public PDFDocument(URL myUrl){
        isValid = this.loadPDF(myUrl);
    }

    //Load A PDF from a local file path 
    public boolean loadPDF(File newFile){
        if (isPDF(newFile)){
            pdfFile = newFile;
            pdfPath = newFile.getAbsolutePath();
            return true;
        }else{
            return false;
        }
    }
    
    //Load a PDF from a URL
    public boolean loadPDF(URL myUrl) {
        try {
            //Open a connection to the URL
            URLConnection connection = myUrl.openConnection();
            connection.connect();
    
            //Check if the content type is PDF
            String fileName = myUrl.getFile();
            if (fileName != null && fileName.endsWith(".pdf")) {
                //Attempt to read the PDF content from the URL
                InputStream inputStream = connection.getInputStream();
                //Set the outputStream to write the data to the file
                ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
                byte[] buffer = new byte[4096];
                //Loop Through The InputStream Until Their Is No More Data To Read
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
                //Convert the OutputStream To a ByteArray
                byte[] pdfContent = outputStream.toByteArray();

                // Create a temporary file to store the PDF content
                File tempFile = File.createTempFile("temp", ".pdf");
                //Add the fileOutputStream to the temporary file
                FileOutputStream fileOutputStream = new FileOutputStream(tempFile);
                //Then write the ByteArray to the pdf
                fileOutputStream.write(pdfContent);
                //close the output stream after finished with it
                fileOutputStream.close();

                if (isPDF(tempFile)) {
                    //If so save the temporary file to the class variables
                    pdfFile = tempFile;
                    pdfPath = tempFile.getAbsolutePath(); 
                    return true;

                //Otherwise output the error and return false
                }else{
                    System.out.println("Error: the file at URL " + myUrl.toString() + " is not a PDF file");
                    return false;
                }

            //If the content type is not a pdf or doesn't exist then their is no pdf file to load
            }else{
                System.out.println("Error: the URL " + myUrl.toString() + " does not point to a PDF file");
                return false;
            }
  
        //If their are any problems throw the error    
        }catch (Exception e) {
            System.out.println("Error: a problem occurred while loading the PDF file from URL " + myUrl.toString());
            e.printStackTrace();
            return false;
        }
    }
    
    //Checks the header of the file to determine if the file is a PDF
    private boolean isPDF(File file){
        String filePath = "";

        try{
            filePath = file.getAbsolutePath();
        }catch(Exception e){
            System.out.println("The file contains no file path");
            e.printStackTrace();
            return false;
        }

        //Ensures That The File Path Leads To A File Not To A Directory
        if (!file.isFile()) {
            System.out.println("Error: the file at location: " + filePath + " does not lead to a file");
            return false;
        }
        //Ensures That The File Is Set To Readable (and therefore can be read)
        if (!file.canRead()) {
            System.out.println("Error: the file at location: " + filePath + " is not readable");
            return false;
        }
        //Ensures that the file has a minimum length of 4 bytes (The PDF Header is %PDF)
        if (file.length() < 4) {
            System.out.println("Error: the file at location: " + filePath + " does not contain the %PDF header");
            return false;
        }

        //set the variable to store the header
        byte[] header = new byte[4];
        //attempt to get the header from the input stream
        try {
            FileInputStream inputStream = new FileInputStream(file);
            inputStream.read(header, 0, 4);
            inputStream.close();
        }
        //If a problem occurs while reading the file return false
        catch(Exception e){
            System.out.println("Error: a problem occured reading the file at location: " + filePath);
            e.printStackTrace();
            return false;
        }

        //Convert the header to a String
        String headerString = new String(header);

        //Return if the file is a pdf (if the header contains %PDF)
        return headerString.equals("%PDF");
    }
}