Java 给PDF签名时添加可信时间戳的方法

<repositories>
        <repository>
            <id>com.e-iceblue</id>
            <url>http://repo.e-iceblue.cn/repository/maven-public/</url>
        </repository>
    </repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.pdf.free</artifactId>
        <version>4.4.1</version>
    </dependency>
</dependencies>

import com.spire.pdf.*;
import com.spire.pdf.graphics.PdfImage;
import com.spire.pdf.graphics.PdfTrueTypeFont;
import com.spire.pdf.security.GraphicMode;
import com.spire.pdf.security.PdfCertificate;
import com.spire.pdf.security.PdfCertificationFlags;
import com.spire.pdf.security.PdfSignature;

import java.awt.*;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;

public class TimeStamp {
    public static void main(String[] args) {
        //加载PDF文档
        PdfDocument pdf = new PdfDocument();
        pdf.loadFromFile("test.pdf");

        //加载pfx证书，及证书秘钥
        PdfCertificate cert = new PdfCertificate("pfx证书","密钥");

        //添加数字签名到指定页面，并设置其位置和大小
        PdfSignature signature = new PdfSignature(pdf, pdf.getPages().get(2), cert, "Mia");
        Rectangle2D rect = new Rectangle2D.Float();
        rect.setFrame(new Point2D.Float((float) pdf.getPages().get(0).getActualSize().getWidth() - 340, (float) pdf.getPages().get(0).getActualSize().getHeight() - 230), new Dimension(280, 120));
        signature.setBounds(rect);

        //设置签名为图片加文本模式
        signature.setGraphicMode(GraphicMode.Sign_Image_And_Sign_Detail);

        //设置签名的内容
        signature.setNameLabel("签字人：");
        signature.setName("Manager");
        signature.setDateLabel("日期：");
        signature.setDate(new java.util.Date());
        signature.setLocationInfoLabel("地点：");
        signature.setLocationInfo("成都");
        signature.setReasonLabel("原因：");
        signature.setReason("文档管理者");
        signature.setDistinguishedNameLabel("DN: ");
        signature.setDistinguishedName(signature.getCertificate().get_IssuerName().getName());
        signature.setSignImageSource(PdfImage.fromFile("sign.png"));

        //设置签名的字体
        signature.setSignDetailsFont(new PdfTrueTypeFont(new Font("Arial Unicode MS", Font.PLAIN, 9)));

        //设置文档权限为禁止更改
        signature.setDocumentPermissions(PdfCertificationFlags.Forbid_Changes);
        signature.setCertificated(true);

        //配置时间戳服务器
        String timestampeServerUrl = "时间戳服务器地址";
        signature.configureTimestamp(timestampeServerUrl);

        //保存文档
        pdf.saveToFile("SignatureWithTimeStamp.pdf");
        pdf.close();
    }
}