如何在 Java 中解析 PDF（開發人員教程）

先決條件

To make a PDF Parsing project in Java, you will need the following tools:

1. Java IDE: You can use any Java-supported IDE. There are multiple Java IDEs available for development. Here this tutorial will be using IntelliJ IDE. You can use NetBeans, Eclipse, etc.
2. Maven Project: Maven is a dependency manager and allows control over the Java project. Maven for Java can be downloaded from the Maven official website. IntelliJ Java IDE has built-in support for Maven.

3. IronPDF - You can download and install IronPDF for Java in multiple ways.

   • Adding IronPDF dependency in the pom.xml file in a Maven project.

     <dependency>
      <groupId>com.ironsoftware</groupId>
      <artifactId>ironpdf</artifactId>
      <version>[LATEST_VERSION]</version>
     </dependency>

     <dependency>
      <groupId>com.ironsoftware</groupId>
      <artifactId>ironpdf</artifactId>
      <version>[LATEST_VERSION]</version>
     </dependency>

     XML
   • Visit the Maven repository website for the latest IronPDF package for Java.
   • A direct download from the Iron Software official download page.
   • Manually install IronPDF using the JAR file in your simple Java Application.

4. Slf4j-Simple: This dependency is also required to stamp content to an existing document. It can be added using the Maven dependencies manager in IntelliJ, or it can be directly downloaded from the Maven website. Add the following dependency to the pom.xml file:

   <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-simple</artifactId>
       <version>2.0.5</version>
   </dependency>

   <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-simple</artifactId>
       <version>2.0.5</version>
   </dependency>

   XML

Adding the Necessary Imports

Once all the prerequisites are installed, the first step is to import the necessary IronPDF packages to work with a PDF document. Add the following code on top of the Main.java file:

import com.ironsoftware.ironpdf.*;
import java.io.IOException;
import java.nio.file.Paths;

import com.ironsoftware.ironpdf.*;
import java.io.IOException;
import java.nio.file.Paths;

License Key

Some methods available in IronPDF require a license to be used. You can purchase a license or try IronPDF free in a free trial. You can set the key as follows:

License.setLicenseKey("YOUR-KEY");

License.setLicenseKey("YOUR-KEY");

Step 1: Parse an Existing PDF document

To parse an existing document for content extraction, the PdfDocument class is used. Its static fromFile method is used to parse a PDF file from a specific path with a specific file name in a Java program. The code is as follows:

PdfDocument parsedDocument = PdfDocument.fromFile(Paths.get("sample.pdf"));

PdfDocument parsedDocument = PdfDocument.fromFile(Paths.get("sample.pdf"));

Parsed document

Step 2: Extract Text Data from Parsed PDF file

IronPDF for Java provides an easy method for extracting text from PDF documents. The following code snippet is for extracting text data from a PDF file is below:

String extractedText = parsedDocument.extractAllText();

String extractedText = parsedDocument.extractAllText();

The above code produces the output given below:

輸出

Step 3: Extract Text Data from URLs or HTML String

The capability of IronPDF for Java is not only restricted to existing PDFs, but it can also create and parse a new file to extract content. Here, this tutorial will create a PDF file from a URL and extract content from it. The following example shows how to achieve this task:

public class Main {
    public static void main(String[] args) throws IOException {
        License.setLicenseKey("YOUR-KEY");

        PdfDocument parsedDocument = PdfDocument.renderUrlAsPdf("https://ironpdf.com/java/");
        String extractedText = parsedDocument.extractAllText();
        System.out.println("Text Extracted from URL:\n" + extractedText);
    }
}

public class Main {
    public static void main(String[] args) throws IOException {
        License.setLicenseKey("YOUR-KEY");

        PdfDocument parsedDocument = PdfDocument.renderUrlAsPdf("https://ironpdf.com/java/");
        String extractedText = parsedDocument.extractAllText();
        System.out.println("Text Extracted from URL:\n" + extractedText);
    }
}

輸出如下：

輸出

Step 4: Extract Images from Parsed PDF Document

IronPDF also provides an easy option to extract all images from parsed documents. Here the tutorial will use the previous example to see how easily the images are extracted from the PDF files.

import com.ironsoftware.ironpdf.*;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class Main {
    public static void main(String[] args) throws IOException {
        License.setLicenseKey("YOUR-KEY");

        PdfDocument parsedDocument = PdfDocument.renderUrlAsPdf("https://ironpdf.com/java/");

        try {
            List<BufferedImage> images = parsedDocument.extractAllImages();
            System.out.println("Number of images extracted from the website: " + images.size());

            int i = 0;
            for (BufferedImage image : images) {
                ImageIO.write(image, "PNG", Files.newOutputStream(Paths.get("assets/extracted_" + ++i + ".png")));
            }
        } catch (Exception exception) {
            System.out.println("Failed to extract images from the website");
            exception.printStackTrace();
        }
    }
}

import com.ironsoftware.ironpdf.*;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class Main {
    public static void main(String[] args) throws IOException {
        License.setLicenseKey("YOUR-KEY");

        PdfDocument parsedDocument = PdfDocument.renderUrlAsPdf("https://ironpdf.com/java/");

        try {
            List<BufferedImage> images = parsedDocument.extractAllImages();
            System.out.println("Number of images extracted from the website: " + images.size());

            int i = 0;
            for (BufferedImage image : images) {
                ImageIO.write(image, "PNG", Files.newOutputStream(Paths.get("assets/extracted_" + ++i + ".png")));
            }
        } catch (Exception exception) {
            System.out.println("Failed to extract images from the website");
            exception.printStackTrace();
        }
    }
}

The [extractAllImages](/java/object-reference/api/com/ironsoftware/ironpdf/PdfDocument.html#extractAllImages()) method returns a list of BufferedImages. Each BufferedImage can then be stored as PNG images on a location using the ImageIO.write method. There are 34 images in the parsed PDF file and every image is perfectly extracted.

Extracted images

Step 5: Extract Data from Table in PDF Files

Extracting content from tabular boundaries in a PDF file is made easy with just a one-line code using the [extractAllText method](/java/object-reference/api/com/ironsoftware/ironpdf/PdfDocument.html#extractAllText()). The following code snippet demonstrates how to extract text from a table in a PDF file:

Table in PDF

PdfDocument parsedDocument = PdfDocument.fromFile(Paths.get("table.pdf"));
String extractedText = parsedDocument.extractAllText();
System.out.println(extractedText);

PdfDocument parsedDocument = PdfDocument.fromFile(Paths.get("table.pdf"));
String extractedText = parsedDocument.extractAllText();
System.out.println(extractedText);

輸出如下：

輸出