如何修复Exception in thread "main" java.lang.NoSuchMethodError异常？附Docx转PDF代码

First, let's tackle that error you're seeing: java.lang.NoSuchMethodError: org.apache.poi.POIXMLDocumentPart.getPackageRelationship. This almost always boils down to dependency version conflicts in your project. You're likely mixing different versions of Apache POI libraries (like poi and poi-ooxml) or using a PDF conversion library that's incompatible with your POI version.

Step 1: Fix Dependencies #

To resolve the conflict, ensure all your Apache POI-related dependencies use the same stable version. Below are the correct dependencies for Maven and Gradle, including the necessary libraries for DOCX-to-PDF conversion (we use OpenPDF here to avoid iText's licensing issues):

Maven (pom.xml) #

<!-- Apache POI core for handling Office files -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>5.2.5</version>
</dependency>
<!-- POI for OOXML (DOCX) support -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>5.2.5</version>
</dependency>
<!-- Full OOXML support required for PDF conversion -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml-full</artifactId>
    <version>5.2.5</version>
</dependency>
<!-- OpenPDF for PDF generation (replaces iText) -->
<dependency>
    <groupId>com.github.librepdf</groupId>
    <artifactId>openpdf</artifactId>
    <version>1.3.30</version>
</dependency>

Gradle (build.gradle) #

implementation 'org.apache.poi:poi:5.2.5'
implementation 'org.apache.poi:poi-ooxml:5.2.5'
implementation 'org.apache.poi:poi-ooxml-full:5.2.5'
implementation 'com.github.librepdf:openpdf:1.3.30'

Step 2: Revised Conversion Code #

Your original code had a few issues (like unclosed streams and limited exception handling). Here's a polished version that follows Java best practices, handles resources properly, and ensures consistent formatting in the output PDF:

import org.apache.poi.xwpf.usermodel.XWPFDocument;
import org.apache.poi.xwpf.converter.pdf.PdfConverter;
import org.apache.poi.xwpf.converter.pdf.PdfOptions;

import java.io.*;

public class DocxToPdfConverter {
    public static void main(String[] args) {
        DocxToPdfConverter converter = new DocxToPdfConverter();
        System.out.println("Starting DOCX to PDF conversion...");
        
        try {
            converter.convertToPdf("D:\\doctopdf.docx", "D:\\Test1.pdf");
            System.out.println("Conversion done! Check your output PDF at D:\\Test1.pdf");
        } catch (Exception e) {
            System.err.println("Conversion failed with error: " + e.getMessage());
            e.printStackTrace(); // Prints full stack trace for easier debugging
        }
    }

    public void convertToPdf(String docxFilePath, String pdfOutputPath) throws IOException {
        // Use try-with-resources to auto-close streams (prevents resource leaks)
        try (InputStream docxInput = new FileInputStream(new File(docxFilePath));
             XWPFDocument docxDocument = new XWPFDocument(docxInput);
             OutputStream pdfOutput = new FileOutputStream(new File(pdfOutputPath))) {

            PdfOptions pdfOptions = PdfOptions.create();
            
            // Optional: Uncomment below to fix Chinese/non-English character rendering
            // pdfOptions.fontProvider((familyName, encoding, size, style, color) -> {
            //     try {
            //         return BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);
            //     } catch (Exception e) {
            //         return null; // Fallback to default font if custom font fails
            //     }
            // });

            // Perform the conversion
            PdfConverter.getInstance().convert(docxDocument, pdfOutput, pdfOptions);
        }
    }
}

Key Improvements & Notes #

• Auto-closed Resources: The try-with-resources syntax ensures all input/output streams and the document are closed automatically, even if an error occurs.
• Better Exception Handling: We catch general exceptions and print the full stack trace, which helps diagnose any remaining issues quickly.
• Font Support: If your DOCX contains non-English characters (like Chinese), uncomment the font provider code and ensure the specified font is available on your system (or embed it in your project).
• Consistent Formatting: Using the matching POI and OpenPDF versions ensures that the PDF retains the original DOCX's layout, fonts, and styling as closely as possible.

内容的提问来源于stack exchange，提问作者Jasir