有没有人知道如何使用 openpdf java lib 为现有 pdf 设置密码？

Question

如何使用 OpenPdf java 库为现有 PDF 设置密码？我试过下面的代码，但是创建了没有内容的新 pdf

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.Paragraph;
import com.lowagie.text.pdf.PdfWriter;

public class PasswordProtectedPDF {
  public static final String ENCRYPTED_PDF = "F://knpcode//result//OpenPDF//PP.pdf";
  // User and owner password
  final static String USER_PASSWORD = "user";
  final static String OWNER_PASSWORD = "owner";
  public static void main(String[] args) {
    try {
      Document doc = new Document();
      PdfWriter writer = PdfWriter.getInstance(doc, new FileOutputStream(ENCRYPTED_PDF));
      // set password, user permissions and encryption
      writer.setEncryption(USER_PASSWORD.getBytes(), OWNER_PASSWORD.getBytes(), PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128); 
      doc.open();
 
     
      doc.close();
      writer.close();
    } catch (DocumentException | FileNotFoundException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
}

Answer 1

要为新 PDF 添加密码，我们使用 PdfWriter.setEncryption() 方法。

PdfStamper API 当我们需要保护现有的 PDF 时使用。在实例化 PdfStamper 时，它接受源文件作为 PdfReader，目标文件作为 OutputStream。 PdfStamper 可以在写入目标文件时在 PDF 中添加一些额外的内容。 PdfStamper.setEncryption 在为现有 PDF 设置加密时使用与 PdfWriter.setEncryption 相同的参数。

已更新您的代码以使用 PDFStamper 而不是 PDFWriter。


    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import com.lowagie.text.Paragraph;
    import com.lowagie.text.pdf.PdfStamper;
    
    public class PasswordProtectedPDF {
      // User and owner password
      final static String USER_PASSWORD = "user";
      final static String OWNER_PASSWORD = "owner";
      public static void main(String[] args) {
        try {
          File f = new File("F://knpcode//result//OpenPDF//ENCRYPTED_PP.pdf");
          FileOutputStream out = new FileOutputStream(f);
          PdfReader reader = new PdfReader("F://knpcode//result//OpenPDF//PP.pdf");
          PdfStamper stamper = new PdfStamper(reader, out);
          
          // set password, user permissions and encryption
          stamper.setEncryption(USER_PASSWORD.getBytes(), OWNER_PASSWORD.getBytes(), PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128);

          // Don't forget to add this line as no bytes are written to that output stream up until you close the PdfStamper instance. 
          stamper.close();

        } catch ( IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
    }

Answer 2

使用 Google“java openpdf 密码示例”我找到了这个网站：https://knpcode.com/java-programs/password-protected-pdf-using-openpdf-java/，其中包含有关您的问题的一些信息。

这里有两个示例程序（只是 copy/pasted 它们，不是测试）。不要忘记 包括 Bouncy Castle 作为安全提供程序。

加密（“保护”）PDF：

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.Paragraph;
import com.lowagie.text.pdf.PdfWriter;

public class PasswordProtectedPDF {
  public static final String ENCRYPTED_PDF = "F://knpcode//result//OpenPDF//PP.pdf";
  // User and owner password
  final static String USER_PASSWORD = "user";
  final static String OWNER_PASSWORD = "owner";
  public static void main(String[] args) {
    try {
      Document doc = new Document();
      PdfWriter writer = PdfWriter.getInstance(doc, new FileOutputStream(ENCRYPTED_PDF));
      // set password, user permissions and encryption
      writer.setEncryption(USER_PASSWORD.getBytes(), OWNER_PASSWORD.getBytes(), PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128); 
      doc.open();
      Paragraph para = new Paragraph("Password protected PDF where only content printing is permitted content can't be copied.");
      doc.add(para);
      doc.close();
      writer.close();
    } catch (DocumentException | FileNotFoundException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
}

使用 OpenPDF 阅读受密码保护的 PDF：

import java.io.IOException;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.parser.PdfTextExtractor;

public class ReadPDF {
  // PDF to be read
  public static final String READ_PDF = "F://knpcode//result//OpenPDF//PP.pdf";
  final static String OWNER_PASSWORD = "owner";
  public static void main(String[] args) {
    PdfReader pdfreader = null;
    try {
      pdfreader = new PdfReader(READ_PDF, OWNER_PASSWORD.getBytes());
      // get pages in PDF
      int pages = pdfreader.getNumberOfPages();
      PdfTextExtractor pdfTextExtractor = new PdfTextExtractor(pdfreader);
      // Iterate through pages to read content
      for(int i = 1; i <= pages; i++) {
        // Extract content of each page
        String contentOfPage = pdfTextExtractor.getTextFromPage(i, true);
        System.out.println(contentOfPage );
      }         
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }finally {
      if(pdfreader != null) {
        pdfreader.close();
      }
    }   
  }
}

有没有人知道如何使用 openpdf java lib 为现有 pdf 设置密码？

Does any one have an idea about how to set password to existing pdf using openpdf java lib?

java

spring

openpdf