iText学习 PDF添加密码 ASN1OctetString

加密PDF可以在生成PDF过程中加密， 代码示例：

PdfWriter writer = PdfWriter.getInstance(pdfdoc, new FileOutputStream(pdfFilename));

/** User password. */
    public static byte[] USER = "TEST".getBytes();
    /** Owner password. */
    public static byte[] OWNER = "1234".getBytes();
writer.setEncryption(USER, OWNER, PdfWriter.ALLOW_PRINTING, PdfWriter.STANDARD_ENCRYPTION_128);

writer.createXmpMetadata();

pdfdoc.open();
。。。。。。
pdfdoc.close();


也可以后加工：
用户需求：通过邮件发送给客户的PDF文件，每个文件都有唯一的ID，通过Encrypt处理后，生成的ID注入到PDF文件中。当客户非法传递给其他非付费客户或发布到Internet上后，我们通过分析文件的ID来，对比本地数据库的USER-ID关系，通过法律部门进行维权处理。

主要功能：对已生成好的源PDF文件加入密码策略。通过Encrypt对PDF文件写入ID关键字，并setEncryption修改文档属性为不可修改即可。


★方法setKeywords主要增加关键字；pdf文件不能直接复制，通过计算当前PDF文件的总页数，然后进行一页页的写入。
1．  计算总页数 int n = reader.getNumberOfPages();
2．  新建PDF文件
PdfWriter writer =
PdfWriter.getInstance(document,new FileOutputStream("e:/newPDF.pdf"));
3．   创建写入直接内容对象
PdfContentByte cb = writer.getDirectContent();
4．  写入内容
PdfImportedPage page;
         
           int rotation;
           int i=0;
           while(i<n)
           {
              i++;                  document.setPageSize(reader.getPageSizeWithRotation(i));
              document.newPage();
              page = writer.getImportedPage(reader, i);
              rotation = reader.getPageRotation(i);
                  cb.addTemplate(page, 1f, 0, 0, 1f, 0, 0);
           }
★      方法getKeywords主要取出pdf的文件信息;主要利用PdfReader的方法getInfo取当前PDF文件信息，返回对象为HashMap,输入对应key的val;
System.out.println(map.get("Author"));
       System.out.println(map.get("Keywords"));
文件Encrypt.java如下

package com.txsec.pdf;

import java.io.FileOutputStream;
import java.util.HashMap;

import com.lowagie.text.Document;
import com.lowagie.text.pdf.PdfWriter;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfImportedPage;
import com.lowagie.text.pdf.PdfEncryption;

public class Encrypt {

    public Encrypt() {
       // TODO Auto-generated constructor stub
    }

  
    public static void main(String[] args) {
       setPDFKeywords();
       getKeywords();

    }
  
    public static void setPDFKeywords()
    {
       try{
           PdfReader reader = new PdfReader("E:/1.pdf");
           int n = reader.getNumberOfPages();
           System.out.println("PDF总页数为:"+n);
           Document document = new Document();
           PdfWriter writer = PdfWriter.getInstance(document,new FileOutputStream("e:/newPDF.pdf"));
         
           document.addAuthor("uoovi");
           document.addKeywords("123456789");
           writer.setEncryption(null,null,
                  PdfWriter.ALLOW_MODIFY_ANNOTATIONS|PdfWriter.ALLOW_COPY|PdfWriter.ALLOW_PRINTING,
                  PdfWriter.STANDARD_ENCRYPTION_40);      
                       
           document.open();
            
           PdfContentByte cb = writer.getDirectContent();
           PdfImportedPage page;
         
           int rotation;
           int i=0;
           while(i<n)
           {
              i++;
            document.setPageSize(reader.getPageSizeWithRotation(i));
              document.newPage();
              page = writer.getImportedPage(reader, i);
              rotation = reader.getPageRotation(i);
              cb.addTemplate(page, 1f, 0, 0, 1f, 0, 0);
           }
         
            
           document.close();
           System.out.println("加密成功!");
       }
       catch(Exception e)
       {
           System.out.println(e.getStackTrace());
           System.out.println(e.getMessage());
       }
         
    }

    public static String getKeywords()
    {
       try{
       PdfReader reader = new PdfReader("E:/newPDF.pdf");
       Document document = new Document();
     
     
       HashMap map = reader.getInfo();
       System.out.println(map.toString());
       map.get("Author");
       System.out.println(map.get("Author"));
       System.out.println(map.get("Keywords"));
       return "";
       }
       catch(Exception e)
       {
           System.out.println(e.getMessage());
           return "";
       }
    }
}



调用setEncryption会异常
writer.setEncryption(null,null,
                  PdfWriter.ALLOW_MODIFY_ANNOTATIONS|PdfWriter.ALLOW_COPY|PdfWriter.ALLOW_PRINTING,
                  PdfWriter.STANDARD_ENCRYPTION_40);
Exception in thread "main" java.lang.NoClassDefFoundError: org/bouncycastle/asn1/ASN1OctetString
    at com.lowagie.text.pdf.PdfEncryption.<init>(Unknown Source)
    at com.lowagie.text.pdf.PdfWriter.setEncryption(Unknown Source)
    at com.txsec.pdf.Encrypt.setPDFKeywords(Encrypt.java:39)
    at com.txsec.pdf.Encrypt.main(Encrypt.java:23)

解决办法：下载 bcprov-jdk16-146.jar，然后加入到构建路径中
下载地址：
http://polydistortion.net/bc/download/