使用iText使用PKCS7签名PDF

Question

我有PKCS7字符串，我想用它签署一个pdf。我试图找到一种方法并找到iText，但我不明白如何使用它。任何有建议的人，请分享。

我找到了以下代码

http://cysorz-software-hardware.blogspot.in/2008/11/how-to-sign-pdf-using-itext-and.html

在网址中，只需输入标题＆＃34;带有外部哈希和签名的示例 在Windows证书模式＆＃34;

使用iText，但我不知道如何使用它

    {
    KeyStore ks = KeyStore.getInstance("pkcs12");
    ks.load(new FileInputStream("my_private_key.pfx"), "my_password".toCharArray());
     String alias = (String)ks.aliases().nextElement();
      PrivateKey key = (PrivateKey)ks.getKey(alias, "my_password".toCharArray());
       Certificate[] chain = ks.getCertificateChain(alias);
      PdfReader reader = new PdfReader("original.pdf");
      FileOutputStream fout = new FileOutputStream("signed.pdf");
    PdfStamper stp = PdfStamper.createSignature(reader, fout, '\0');
     PdfSignatureAppearance sap = stp.getSignatureAppearance();
      sap.setCrypto(key, chain, null, PdfSignatureAppearance.WINCER_SIGNED);
    sap.setReason("I'm the author");
    sap.setLocation("Lisbon");
    // comment next line to have an invisible signature
    sap.setVisibleSignature(new Rectangle(100, 100, 200, 200), 1, null);
      sap.setExternalDigest(new byte[128], new byte[20], "RSA");
      sap.preClose();
      MessageDigest messageDigest = MessageDigest.getInstance("SHA1");
       byte buf[] = new byte[8192];
       int n;
      InputStream inp = sap.getRangeStream();
      while ((n = inp.read(buf)) > 0) {
        messageDigest.update(buf, 0, n);
     }
   byte hash[] = messageDigest.digest();
       PdfSigGenericPKCS sg = sap.getSigStandard();
      PdfLiteral slit = (PdfLiteral)sg.get(PdfName.CONTENTS);
     byte[] outc = new byte[(slit.getPosLength() - 2) / 2];
      PdfPKCS7 sig = sg.getSigner();
      Signature sign = Signature.getInstance("SHA1withRSA");
      sign.initSign(key);
     sign.update(hash);
      sig.setExternalDigest(sign.sign(), hash, "RSA");
      PdfDictionary dic = new PdfDictionary();
   byte[] ssig = sig.getEncodedPKCS7();
        System.arraycopy(ssig, 0, outc, 0, ssig.length);
          dic.put(PdfName.CONTENTS, new PdfString(outc).setHexWriting(true));
          sap.close(dic);
             }