java pdf电子签章

Java可以通过使用第三方库来实现PDF电子签章的功能。其中比较常用的有iText和PDFBox。

iText是一个广泛使用的PDF文档处理库，可以在PDF文档中添加数字签名。以下是使用iText实现PDF电子签章的步骤：

1. 加载PDF文件并创建签名区域

PdfReader reader = new PdfReader("original.pdf");
FileOutputStream os = new FileOutputStream("signed.pdf");
PdfStamper stamper = PdfStamper.createSignature(reader, os, '\0');
PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
appearance.setImage(Image.getInstance("signature.png"));
appearance.setReason("I am the author");
appearance.setLocation("China");

2. 创建数字签名

PrivateKey privateKey = (PrivateKey) keystore.getKey("alias", "password".toCharArray());
Certificate[] chain = keystore.getCertificateChain("alias");
PdfSignature dic = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
dic.setReason(appearance.getReason());
dic.setLocation(appearance.getLocation());
dic.setContact(appearance.getContact());
dic.setDate(new PdfDate(appearance.getSignDate()));
appearance.setCrypto(privateKey, chain, null, PdfSignatureAppearance.WINCER_SIGNED);
appearance.setSignatureGraphic(Image.getInstance(signatureGraphic));
appearance.setRenderingMode(PdfSignatureAppearance.RenderingMode.GRAPHIC);
appearance.setVisibleSignature(new Rectangle(36, 748, 144, 780), 1, "sig");
PdfSignature dic2 = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
dic2.setReason(appearance.getReason());
dic2.setLocation(appearance.getLocation());
dic2.setContact(appearance.getContact());
dic2.setDate(new PdfDate(appearance.getSignDate()));
PdfSignatureAppearance appearance2 = PdfStamper.createSignature(reader, null, '\0');
appearance2.setVisibleSignature(new Rectangle(36, 748, 144, 780), 1, "sig");
appearance2.setCrypto(privateKey, chain, null, PdfSignatureAppearance.WINCER_SIGNED);
PdfSignature dic3 = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
dic3.setReason(appearance.getReason());
dic3.setLocation(appearance.getLocation());
dic3.setContact(appearance.getContact());
dic3.setDate(new PdfDate(appearance.getSignDate()));
appearance2.setSignatureGraphic(Image.getInstance(signatureGraphic));
appearance2.setRenderingMode(PdfSignatureAppearance.RenderingMode.GRAPHIC);
PdfDictionary dic4 = new PdfDictionary();
dic4.put(PdfName.CONTENTS, new PdfString("test".getBytes()));

3. 签名并保存PDF文件

PdfSignature dic5 = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
dic5.setReason(appearance.getReason());
dic5.setLocation(appearance.getLocation());
dic5.setContact(appearance.getContact());
dic5.setDate(new PdfDate(appearance.getSignDate()));
appearance4.setCrypto(privateKey, chain, null, PdfSignatureAppearance.WINCER_SIGNED);
appearance4.setSignatureGraphic(Image.getInstance(signatureGraphic));
appearance4.setRenderingMode(PdfSignatureAppearance.RenderingMode.GRAPHIC);
PdfDictionary dic6 = new PdfDictionary();
dic6.put(PdfName.CONTENTS, new PdfString("test".getBytes()));
PdfDictionary dic7 = new PdfDictionary();
dic7.put(PdfName.CONTENTS, new PdfString("test".getBytes()));

以上就是使用iText实现PDF电子签章的基本步骤。值得注意的是，签章的过程中需要使用数字证书，确保签章的真实性和合法性。