Java에서 PDF 파일을 읽는 방법

Prerequisites

To use IronPDF to make a Java PDF reader, it is necessary to ensure that the following components are installed on the computer:

1. JDK - Java Development Kit is required for building and running Java programs. If it is not installed, download it from the Oracle Website.
2. IDE - Integrated Development Environment is software that helps write, edit, and debug a program. Download any IDE for Java, e.g., Eclipse, NetBeans, IntelliJ.
3. Maven - Maven is an automation tool that helps download libraries from the Central Repository. Download it from the Apache Maven Website.
4. IronPDF - Finally, IronPDF is required to read the PDF file in Java. This needs to be added as a dependency in your Java Maven Project. Include the IronPDF artifact along with the slf4j dependency in the pom.xml file as shown in the example below:

<dependencies>

    <dependency>
        <groupId>com.ironsoftware</groupId>
        <artifactId>ironpdf</artifactId>
        <version>your-version-here</version>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.32</version>
    </dependency>
</dependencies>

<dependencies>

    <dependency>
        <groupId>com.ironsoftware</groupId>
        <artifactId>ironpdf</artifactId>
        <version>your-version-here</version>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.32</version>
    </dependency>
</dependencies>

Adding Necessary Imports

Firstly, add the following code on top of the Java source file to reference all the required methods from IronPDF:

import com.ironsoftware.ironpdf.*;
// Necessary imports from IronPDF library

import com.ironsoftware.ironpdf.*;
// Necessary imports from IronPDF library

Next, configure IronPDF with a valid license key to use its methods. Invoke the setLicenseKey method in the main method.

License.setLicenseKey("Your license key");
// Set your IronPDF license key - required for full version

License.setLicenseKey("Your license key");
// Set your IronPDF license key - required for full version

Note: You can get a free trial license key to create, read, and print PDFs.

Read Existing PDF File in Java

To read PDF files, there must be PDF files, or one can be created. This article will use an already created PDF file. The code is simple and a two-step process to extract text from the document:

// Load the PDF document from file
PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/sample.pdf"));
// Extract all text from the PDF
String text = pdf.extractAllText();
// Print the extracted text
System.out.println(text);

// Load the PDF document from file
PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/sample.pdf"));
// Extract all text from the PDF
String text = pdf.extractAllText();
// Print the extracted text
System.out.println(text);

In the above code, fromFile opens a PDF document. The Paths.get method gets the directory of the file and is ready to extract content from the file. Then, [extractAllText](/java/object-reference/api/com/ironsoftware/ironpdf/PdfDocument.html#extractAllText()) reads all the text in the document.

The output is below:

Reading PDF Text Output

Read Text from a Specific Page

IronPDF can also read content from a specific page in a PDF. The extractTextFromPage method uses a PageSelection object to accept a range of page(s) from which text will be read.

In the following example, the text is extracted from the second page of the PDF document. PageSelection.singlePage takes the index of the page which needs to be extracted (index starting from 0).

// Load the PDF document from file
PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/sample.pdf"));
// Extract text from the second page (page index based, starts at 0, so 1 means second page)
String text = pdf.extractTextFromPage(PageSelection.singlePage(1));
// Print the extracted text from the specified page
System.out.println(text);

// Load the PDF document from file
PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/sample.pdf"));
// Extract text from the second page (page index based, starts at 0, so 1 means second page)
String text = pdf.extractTextFromPage(PageSelection.singlePage(1));
// Print the extracted text from the specified page
System.out.println(text);

Reading PDF Text Output

Other methods available in the PageSelection class which can be used to extract text from various pages include: [firstPage](/java/object-reference/api/com/ironsoftware/ironpdf/edit/PageSelection.html#lastPage()), [lastPage](/java/object-reference/api/com/ironsoftware/ironpdf/edit/PageSelection.html#firstPage()), pageRange, and [allPages](/java/object-reference/api/com/ironsoftware/ironpdf/edit/PageSelection.html#allPages()).

Read Text from a Newly-Generated PDF File

Search text can also be performed from a newly generated PDF file from either an HTML file or URL. The following sample code generates PDFs from URL and extracts all text from the website.

// Generate PDF from a URL
PdfDocument pdf = PdfDocument.renderUrlAsPdf("https://unsplash.com/");
// Extract all text from the generated PDF
String text = pdf.extractAllText();
// Print the extracted text from the URL
System.out.println("Text extracted from the website: " + text);

// Generate PDF from a URL
PdfDocument pdf = PdfDocument.renderUrlAsPdf("https://unsplash.com/");
// Extract all text from the generated PDF
String text = pdf.extractAllText();
// Print the extracted text from the URL
System.out.println("Text extracted from the website: " + text);

Read from a New File

IronPDF can also be used to extract images from PDF files.

The complete code is as follows:

import com.ironsoftware.ironpdf.License;
import com.ironsoftware.ironpdf.PdfDocument;
import com.ironsoftware.ironpdf.edit.PageSelection;

import java.io.IOException;
import java.nio.file.Paths;

public class Main {
    public static void main(String[] args) throws IOException {
        // Set the IronPDF license key for commercial use
        License.setLicenseKey("YOUR LICENSE KEY HERE");

        // Read text from a specific page in an existing PDF
        PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/sample.pdf"));
        String text = pdf.extractTextFromPage(PageSelection.singlePage(1));
        System.out.println(text);

        // Read all text from a PDF generated from a URL
        pdf = PdfDocument.renderUrlAsPdf("https://unsplash.com/");
        text = pdf.extractAllText();
        System.out.println("Text extracted from the website: " + text);
    }
}

import com.ironsoftware.ironpdf.License;
import com.ironsoftware.ironpdf.PdfDocument;
import com.ironsoftware.ironpdf.edit.PageSelection;

import java.io.IOException;
import java.nio.file.Paths;

public class Main {
    public static void main(String[] args) throws IOException {
        // Set the IronPDF license key for commercial use
        License.setLicenseKey("YOUR LICENSE KEY HERE");

        // Read text from a specific page in an existing PDF
        PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/sample.pdf"));
        String text = pdf.extractTextFromPage(PageSelection.singlePage(1));
        System.out.println(text);

        // Read all text from a PDF generated from a URL
        pdf = PdfDocument.renderUrlAsPdf("https://unsplash.com/");
        text = pdf.extractAllText();
        System.out.println("Text extracted from the website: " + text);
    }
}