如何使用Java对带有可见签名和文本的PDF文档进行数字签名

问题描述

我正在尝试使用Java使用PDFBox Library对PDF文件进行数字签名，并在其中将可见文本显示在签名字段（如附件图像）上。我尝试了以下代码，并收到以下警告，

WARN org.apache.pdfBox.pdmodel.interactive.form.PDSignatureField- 尚未实现的签名字段的外观生成-您 需要手动生成/更新

以下是代码

PDDocument pDDocument = PDDocument.load(new File("input.pdf"));
PDDocumentCatalog pDDocumentCatalog = pDDocument.getDocumentCatalog();
PDAcroForm pDAcroForm = pDDocumentCatalog.getAcroForm();
PDSignatureField pDSignatureField = (PDSignatureField) pDAcroForm.getField("signatureField");
PDSignature pDSignature = new PDSignature();

KeyStore keyStore = KeyStore.getInstance("PKCS12");
keyStore.load(new FileInputStream("pfxfile.pfx"),"password".tochararray());
byte[] bytes = IoUtils.toByteArray(new FileInputStream("pfxfile.pfx"));
pDSignature.setContents(bytes);

pDSignatureField.setValue(pDSignature);
FileOutputStream fileOutputStream = new FileOutputStream("output.pdf");
pDDocument.saveIncremental(fileOutputStream);

那么我在做什么错了？还是除了PDFBox之外还有其他解决方案吗？

解决方法

您可以使用iText轻松做到这一点。这是使用iText 7的有效解决方案。您可以从他们的examples中查看更多信息。

public static void digitalSignature(String sourceFile,String signatureFieldName,String outputFile,Certificate[] certificateChain,PrivateKey privateKey,String digestAlgorithm,String bouncyCastleProvider,PdfSigner.CryptoStandard cryptoStandardSubFilter,String reason,String location)
        throws GeneralSecurityException,IOException {

    PdfReader pdfReader = new PdfReader(sourceFile);
    PdfSigner pdfSigner = new PdfSigner(pdfReader,new FileOutputStream(outputFile),new StampingProperties());

    // Create the signature appearance
    PdfSignatureAppearance pdfSignatureAppearance = pdfSigner.getSignatureAppearance()
            .setReason(reason)
            .setLocation(location);

    // This name corresponds to the name of the field that already exists in the document.
    pdfSigner.setFieldName(signatureFieldName);

    pdfSignatureAppearance.setRenderingMode(PdfSignatureAppearance.RenderingMode.NAME_AND_DESCRIPTION);

    IExternalSignature iExternalSignature = new PrivateKeySignature(privateKey,digestAlgorithm,bouncyCastleProvider);
    IExternalDigest iExternalDigest = new BouncyCastleDigest();

    // Sign the document using the detached mode,CMS,or CAdES equivalent.
    pdfSigner.signDetached(iExternalDigest,iExternalSignature,certificateChain,null,cryptoStandardSubFilter);
}

public static void main(String[] args) throws IOException,GeneralSecurityException {
    BouncyCastleProvider bouncyCastleProvider = new BouncyCastleProvider();
    Security.addProvider(bouncyCastleProvider);

    KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
    keyStore.load(new FileInputStream("path/to/keystore/file"),"password".toCharArray());
    String alias = keyStore.aliases().nextElement();
    PrivateKey privateKey = (PrivateKey) keyStore.getKey(alias,"password".toCharArray());
    Certificate[] certificateChain = keyStore.getCertificateChain(alias);

    digitalSignature("path/to/input.pdf","Signature Field Name","path/to/output.pdf",privateKey,DigestAlgorithms.SHA256,bouncyCastleProvider.getName(),PdfSigner.CryptoStandard.CMS,"Reason","Location");
}