itext實現合同尾部簽章部分自動添加，定位簽名

使用的pom

<!-- pdf處理 start-->
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itext-asian</artifactId>
    <version>5.2.0</version>
</dependency>
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.4</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.itextpdf/kernel -->
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>kernel</artifactId>
    <version>7.1.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.itextpdf/layout -->
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>layout</artifactId>
    <version>7.1.2</version>
</dependency>
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk15on</artifactId>
    <version>1.49</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.itextpdf/forms -->
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>forms</artifactId>
    <version>7.1.4</version>
</dependency>
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15on</artifactId>
    <version>1.49</version>
</dependency>
<!-- pdf處理 end-->

效果圖

原理

1. 通過itext中List添加固定文本
2. 添加指定標記比如★☆用以之后替換成其他文本或圖片
3. 可以不用標記，反正就是算好位置
4. 至於簽章這塊位置的選定，根據文檔最后一行位置判定，我的判定方法就是文檔最后一頁最后一行離尾部距離小於一定值，簽章的整塊內容移到新的一頁

過程

1. 核心利用了com.itextpdf.text.pdf.parser.RenderListener這個類，它會遍歷這個文檔的內容
2. 寫個繼承這個類的方法，實現方法如下

@Override
public void renderText(TextRenderInfo textInfo) {
    Float bound = textInfo.getBaseline().getBoundingRectange();
    String text = textInfo.getText();
    float y = bound.y - this.fixHeight;
    for (String keyWord : findText) {
        if (null != text && text.contains(keyWord)) {
            ReplaceRegion region = new ReplaceRegion(keyWord);
            region.setH(bound.height == 0 ? defaultH : bound.height);
            if ((text.contains("☆") && keyWord.equals("☆"))) {
                region.setW(20f);
                int i = text.indexOf("☆");
                region.setX(bound.x + 13 * i);
            } else if (text.contains("★") && keyWord.equals("★")) {
                region.setW(15f);
                region.setX(bound.x);
            } else if ((text.contains("△") && keyWord.equals("△"))) {
                region.setW(15f);
                int i = text.indexOf("△");
                region.setX(bound.x + 11 * i);
            } else if ((text.contains("▲") && keyWord.equals("▲"))) {
                region.setW(15f);
                region.setX(bound.width + 15 * 4.5f);
            } else {
                region.setW(bound.width);
                region.setX(bound.x);
            }
            region.setY(y);
            result.put(keyWord, region);
        }
    }
    //判斷最后一行是否小於某個值
    if (y < heightSign) {
        signY.put("endY", 0f);
    } else {
        signY.put("endY", y);
    }
}

3. 這里我進行了很多微調，此方法肯定存在很多改進的地方，由於時間緊急，我對itext的研究也不深，勉強實現需求

...
PdfReader reader = new PdfReader(pdfBytes);
//內容解析器
PdfReaderContentParser parser = new PdfReaderContentParser(reader);
for (int i = 1; i <= numberOfPages; i++) {
    parser.processContent(i, listener);
    Map<String, ReplaceRegion> res = listener.getResult(i);
    if (res.size() > 0) {
        pdfReplacer.setPageNum(i);
        result = res;
    }
}
...

5. 通過上面的步驟找到最后一行位置，找到指定特殊字符的位置
6. 添加尾部簽章部分通過

PdfReader reader = new PdfReader(basePath + "_temp2.pdf");
PdfWriter writer = new PdfWriter(basePath + "_temp3.pdf");
PdfDocument pdf = new PdfDocument(reader, writer);
int numberOfPages = pdf.getNumberOfPages();
float height = pdf.getDefaultPageSize().getHeight();
if (endY == 0f) {
    numberOfPages++;
    endY = height - 140f;
    pdf.addNewPage();
}else{
    endY = endY - 60f;
}

Document doc = new Document(pdf);
PdfFont font = PdfFontFactory.createFont("C:/Windows/Fonts/simsun.ttc,1", PdfEncodings.IDENTITY_H,true);
com.itextpdf.layout.element.List list = new com.itextpdf.layout.element.List().setPageNumber(numberOfPages).setFixedPosition(80,endY,400f).setListSymbol("").setSymbolIndent(22f).setFont(font).setFontSize(14);
list.add(new ListItem("甲方法定代表人：☆            乙方法定代表人： △"))
    .add(new ListItem("聯系電話：                    聯系電話："))
    .add(new ListItem("身份證號碼：                  身份證號碼："))
    .add(new ListItem("★                            ▲"));
doc.add(list);

pdf.close();

7. 整個過程會出現很多中間臨時文件，所以說還是可以有很多改進的地方。

8. 替換方法，用來替換日期，和覆蓋特殊符號

textReplacer = new PdfReplacer(basePath + "_temp3.pdf");
textReplacer.replaceText(replaceStr, destStr.toString());
replaceRegion = textReplacer.toPdf(basePath + "_temp4.pdf");
PdfReplacer textReplacer2 = new PdfReplacer(basePath + "_temp4.pdf");
String dateRecord = sysconfig.getProperties().getProperty(dateSign);
String text = DateUtil.format2str("yyyy 年  MM 月  dd 日");
textReplacer2.setFont(14);
String dateFontPath = sysconfig.getProperties().getProperty("date_font_path");
if (dateFontPath.lastIndexOf("ttf") > 0) {
    textReplacer2.setFont(new com.itextpdf.text.Font(BaseFont.createFont(dateFontPath, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED)));
} else {
    dateFontPath = dateFontPath + ",1";
    textReplacer2.setFont(new com.itextpdf.text.Font(BaseFont.createFont(dateFontPath, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED)));
}
log.info("字體路徑{}", dateFontPath);
textReplacer2.replaceText(dateRecord, text);

9. 簽章方法

public static byte[] sign(String password, InputStream inputStream, String signPdfSrc, String signImage,
                          float x, float y,int page) {
    File signPdfSrcFile = new File(signPdfSrc);
    PdfReader reader = null;
    ByteArrayOutputStream signPDFData = null;
    PdfStamper stp = null;
    try {
        BouncyCastleProvider provider = new BouncyCastleProvider();
        Security.addProvider(provider);
        KeyStore ks = KeyStore.getInstance("PKCS12", new BouncyCastleProvider());
        // 私鑰密碼 為Pkcs生成證書是的私鑰密碼 123456
        ks.load(inputStream, password.toCharArray());
        String alias = (String) ks.aliases().nextElement();
        PrivateKey key = (PrivateKey) ks.getKey(alias, password.toCharArray());
        Certificate[] chain = ks.getCertificateChain(alias);
        reader = new PdfReader(signPdfSrc);
        signPDFData = new ByteArrayOutputStream();
        // 臨時pdf文件
        File temp = new File(signPdfSrcFile.getParent(), System.currentTimeMillis() + ".pdf");
        stp = PdfStamper.createSignature(reader, signPDFData, '\0', temp, true);
        stp.setFullCompression();
        PdfSignatureAppearance sap = stp.getSignatureAppearance();
        sap.setReason("數字簽名，不可改變");
        // 使用png格式透明圖片
        Image image = Image.getInstance(signImage);
        sap.setImageScale(0);
        sap.setSignatureGraphic(image);
        sap.setRenderingMode(RenderingMode.GRAPHIC);
        int size = 120;
        // 是對應x軸和y軸坐標
        float lly = y - 50;
        sap.setVisibleSignature(new Rectangle(x, lly, x + size, lly+size), page,
                UUID.randomUUID().toString().replaceAll("-", ""));
        stp.getWriter().setCompressionLevel(5);
        ExternalDigest digest = new BouncyCastleDigest();
        ExternalSignature signature = new PrivateKeySignature(key, DigestAlgorithms.SHA512, provider.getName());
        MakeSignature.signDetached(sap, digest, signature, chain, null, null, null, 0, CryptoStandard.CADES);
        stp.close();
        reader.close();
        return signPDFData.toByteArray();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {

        if (signPDFData != null) {
            try {
                signPDFData.close();
            } catch (IOException e) {
            }
        }

        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (IOException e) {
            }
        }
    }
    return null;
}