Java Program to Extract Content from a PDF

To extract content from a PDF in Java, there are a number of libraries that are available such as the Apache PDFBox. Apache PDFBox is one of the best libraries that is used to perform various operations on PDFs like PDF to text extraction, PDF generation, and many more.

Prerequisites

Apache PDFBox Library: First of all, we must add the PDFBox library to your project. It can be downloaded from the official website or declared as the project's dependency in the build tool such as Maven or Gradle.

For Maven:

<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>2.0.27</version>
</dependency>

For Gradle:

Step-by-Step Guide

Setting Up the Project: Import the PDFBox library into the Java project.

Creating the Java Class: Develop a Java class that will be solely responsible for the extraction of text from a PDF file.

Using PDFBox to Extract Text: Load a PDF document and read it using the PDFBox API to obtain the text of the document.

Handling Exceptions: Ensure that you cater for exception errors such as file not found errors or read errors where appropriate.

Java Program to Extract Content from a PDF

Alright, let's come up with an elaborate Java code on how to extract text from a PDF document. This program opens a PDF file, parse the contents of that file and then print out the contents on the console.

File Name: PDFTextExtractor.java

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.text.PDFTextStripper;
public class PDFTextExtractor {
    /**
     * Extracts text from a PDF file.
     * @param pdfFilePath The path to the PDF file.
     * @param outputFilePath The path to the output text file.
     */
    public void extractText(String pdfFilePath, String outputFilePath) {
        PDDocument document = null;
        FileWriter writer = null;
        try {
            // Load the PDF document from the specified file
            document = PDDocument.load(new File(pdfFilePath));
            // Check if the document is encrypted
            if (document.isEncrypted()) {
                System.err.println("The document is encrypted and cannot be processed.");
                return;
            }
            // Create a PDFTextStripper object to extract text from the PDF
            PDFTextStripper pdfStripper = new PDFTextStripper();
            // Extract text from the PDF document
            String text = pdfStripper.getText(document);
            // Write the extracted text to the output file
            writer = new FileWriter(outputFilePath);
            writer.write(text);
            System.out.println("Text extracted and written to: " + outputFilePath);
        } catch (IOException e) {
            // Handle exceptions related to file processing
            System.err.println("An error occurred while processing the PDF file: " + e.getMessage());
        } finally {
            // Ensure the document and writer are closed to release resources
            try {
                if (document != null) {
                    document.close();
                }
                if (writer != null) {
                    writer.close();
                }
            } catch (IOException e) {
                System.err.println("An error occurred while closing resources: " + e.getMessage());
            }
        }
    }
    public static void main(String[] args) {
        // Check if the correct number of arguments is provided
        if (args.length != 2) {
            System.err.println("Usage: java PDFTextExtractor <PDF file path> <Output text file path>");
            return;
        }
        // Get the PDF file path and output file path from the arguments
        String pdfFilePath = args[0];
        String outputFilePath = args[1];
        // Create an instance of PDFTextExtractor and extract the text
        PDFTextExtractor extractor = new PDFTextExtractor();
        extractor.extractText(pdfFilePath, outputFilePath);
    }
}

Running the Program

Compile the Program: Ensure you have Apache PDFBox in your classpath and compile the Java program.

javac -cp .:pdfbox-app-2.0.27.jar PDFTextExtractor.java

Run the Program: Execute the program from the command line, providing the path to the input PDF file and the desired output text file.

java -cp .:pdfbox-app-2.0.27.jar PDFTextExtractor input.pdf output.txt

Explanation:

Imports: The required classes from java:io for file operations and org. apache. For PDF processing pdfbox are imported.

PDFTextExtractor Class: This class consists of the methods to extract text from the given PDF file.

extractText() Method: This method completes the primary task of the program, which is to extract text from a chosen PDF file.
Loading the PDF Document: load(new File(pdfFilePath)) loads the PDF file into memory.
Checking for Encryption: If the PDF is encrypted, the method simply prints out an error message and exits the function.
Extracting Text: getText(document) simplifies the extracting of text from the PDF.
Writing to File: It extracted text is then written to the needed output file.
Exception Handling: If there are any I/O exceptions during the file processing, then they are caught and handled.
Resource Cleanup: The finally block guarantees that both the PDDocument and FileWriter are closed to prevent resource leakage.

Argument Check: Checks if the user has supplied the correct number of arguments as required (PDF file path and the output text file path).

Instantiate and Call Extractor: The PDFTextExtractor object is instantiated and the extractText method is invoked with the given arguments.

Conclusion

This Java program shows how Java can use Apache PDFBox library to extract text from PDF files. It takes care of the process of loading the PDF, checking for encryption, extracting the text content from it and then writing the output to another file. There is proper exception handling and resource management, so that there are no problems with a correct functioning of the program.

Apache PDFBox is a very powerful tool for manipulating PDF documents in Java. It has many more features than just text extraction, like document creation, document modification, handling annotations, and more. Here, we have learned how to include PDF text extraction in Java programs, and we can develop it further based on this example.

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