PDF模板填充新姿势，开箱即用

写在前面

由于之前使用Itext5工具填充PDF模板后，会导致填充后的PDF文件体积变得很庞大。

怀疑了嵌入字体、PDF模板编辑转换和编辑等等的原因，但最后都无功而返，查阅了官方文档，也没得出解决方案。

因此，退而求其次，换上了Itext7，官方说过，性能相较Itext5更出色。

依赖

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itext7-core</artifactId>
    <version>8.0.1</version>
    <type>pom</type>
</dependency>
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>bouncy-castle-adapter</artifactId>
    <version>8.0.1</version>
</dependency>

注：引入bouncy-castle-adapter是因为Itext7解析PDF时用到了加密算法，因此可能还需引入

<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk15on</artifactId>
    <version>1.70</version>
</dependency>
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15on</artifactId>
    <version>1.70</version>
</dependency>

工具

import com.itextpdf.forms.PdfAcroForm;
import com.itextpdf.forms.fields.PdfFormCreator;
import com.itextpdf.forms.fields.PdfFormField;
import com.itextpdf.io.font.PdfEncodings;
import com.itextpdf.io.image.ImageData;
import com.itextpdf.io.image.ImageDataFactory;
import com.itextpdf.kernel.events.Event;
import com.itextpdf.kernel.events.IEventHandler;
import com.itextpdf.kernel.events.PdfDocumentEvent;
import com.itextpdf.kernel.font.PdfFont;
import com.itextpdf.kernel.font.PdfFontFactory;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.*;
import com.itextpdf.kernel.pdf.annot.PdfAnnotation;
import com.itextpdf.kernel.pdf.annot.PdfWidgetAnnotation;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.layout.Canvas;
import com.itextpdf.layout.element.Paragraph;
import com.itextpdf.layout.properties.TextAlignment;
import lombok.extern.slf4j.Slf4j;

import java.io.*;
import java.util.HashMap;
import java.util.Map;

/**
 * PDF 模板填充工具类（基于itext7）
 */
@Slf4j
public final class Pdf7TemplateFillUtil {
    /**
     * 待填充的PDF模板文档
     */
    private final transient PdfReader template;

    /**
     * 未填充的表单域可编辑
     */
    private boolean unfilledFormEditable = false;

    /**
     * 显示页码
     */
    private boolean pageNo = false;

    /**
     * 首页显示页码
     */
    private boolean firstPageNo = false;

    /**
     * 填充及返回填充后的数据
     *
     * @param fillData - 待填充数据
     * @return - 填充后bytes数据
     */
    public byte[] fill(Map<String, Object> fillData) throws IOException {
        ByteArrayOutputStream dest = new ByteArrayOutputStream();
        PdfDocument doc = null;
        try {
            PdfFont font = PdfFontFactory.createFont("fons/AlibabaPuHuiTi-3-35-Thin.ttf",// font class path
                    PdfEncodings.IDENTITY_H, PdfFontFactory.EmbeddingStrategy.PREFER_EMBEDDED);

            PdfWriter pdfWriter = new PdfWriter(dest);
            pdfWriter.setCompressionLevel(CompressionConstants.BEST_COMPRESSION);
            doc = new PdfDocument(template, pdfWriter);
            if (pageNo) {
                doc.addEventHandler(PdfDocumentEvent.END_PAGE, new PageNumberEvent(font, firstPageNo));
            }
            PdfAcroForm form = PdfAcroForm.getAcroForm(doc, true);
            for (Map.Entry<String, Object> entry : fillData.entrySet()) {
                String keyword = entry.getKey();
                PdfFormField templateFormField = form.getField(keyword);
                if (templateFormField == null) {
                    continue;
                }
                Object value = entry.getValue();
                if (value instanceof byte[]) {
                    PdfArray pos = templateFormField.getWidgets().get(0).getRectangle();
                    float x = pos.getAsNumber(0).floatValue();
                    float y = pos.getAsNumber(1).floatValue();
                    float width = pos.getAsNumber(2).floatValue() - x;
                    float height = pos.getAsNumber(3).floatValue() - y;
                    Rectangle rectangle = new Rectangle(x, y, width, height);
                    PdfFormField formField = PdfFormCreator.createFormField(new PdfWidgetAnnotation(rectangle), doc);
                    PdfPage annotationPage = findAnnotationPage(doc, keyword);
                    if (annotationPage != null) {
                        doFillFieldImage(annotationPage, formField, (byte[]) value);
                    }
                } else {
                    if (value instanceof Boolean) {
                        templateFormField.setValue(String.valueOf(value), true);
                    } else {
                        templateFormField.setValue(String.valueOf(value));
                    }
                    templateFormField.setFontAndSize(font, templateFormField.getFontSize());
                    templateFormField.setReadOnly(true);
                }
                if (unfilledFormEditable) {
                    form.partialFormFlattening(keyword);
                }
            }
            form.flattenFields();
        } finally {
            if (doc != null && !doc.isClosed()) {
                doc.close();
            }
        }
        return dest.toByteArray();
    }

    /**
     * 启用未填充的表单域可编辑
     */
    public Pdf7TemplateFillUtil unfilledFormEditable() {
        this.unfilledFormEditable = true;
        return this;
    }

    /**
     * 启用页码
     */
    public Pdf7TemplateFillUtil pageNumber() {
        this.pageNo = true;
        return this;
    }

    /**
     * 启用页码
     *
     * @param firstPageNo - 首页显示页码
     */
    public Pdf7TemplateFillUtil pageNumber(boolean firstPageNo) {
        this.pageNo = true;
        this.firstPageNo = firstPageNo;
        return this;
    }

    /**
     * 图片填充
     *
     * @param newPage   - 当前页
     * @param formField - 表单文本域
     * @param imgBytes  - 图片文件字节数组
     */
    private void doFillFieldImage(PdfPage newPage, PdfFormField formField, byte[] imgBytes) {
        Rectangle rtl = formField.getWidgets().get(0).getRectangle().toRectangle(); // 获取表单域的xy坐标
        PdfCanvas canvas = new PdfCanvas(newPage);
        ImageData img = ImageDataFactory.create(imgBytes);
        if (Float.compare(img.getWidth(), rtl.getWidth()) <= 0 && Float.compare(img.getHeight(), rtl.getHeight()) <= 0) {// 不处理
            canvas.addImageAt(img, rtl.getX(), rtl.getY(), true);
        } else {
            // 压缩图片。计算得到图片放缩的最大比例
            float scale = Math.max(img.getWidth() / rtl.getWidth(), img.getHeight() / rtl.getHeight());
            int imgWidth = Math.round(img.getWidth() / scale);
            int imgHeight = Math.round(img.getHeight() / scale);
            // 压缩图片
            byte[] compressImgBytes;
            try {
                compressImgBytes = ImageCompressUtils.resizeByThumbnails(imgBytes, imgWidth, imgHeight);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            img = ImageDataFactory.create(compressImgBytes);
            canvas.addImageAt(img, rtl.getX(), rtl.getY(), true);
        }
    }

    /**
     * 根据表单域关键字查找当前关键字所在页对象（PdfPage）
     *
     * @param keyword - 关键字
     * @return - page object
     */
    private PdfPage findAnnotationPage(PdfDocument doc, String keyword) {
        int pages = doc.getNumberOfPages();
        for (int index = 1; index <= pages; index++) {
            PdfPage page = doc.getPage(index);
            for (PdfAnnotation annotation : page.getAnnotations()) {
                PdfString title = annotation.getPdfObject().getAsString(PdfName.T);
                if (title != null && keyword.equals(String.valueOf(title))) {
                    return page;
                }
            }
        }
        return null;
    }

    /**
     * 获取模板文件表单域关键字位置信息
     */
    private Map<Integer, Map<String, float[]>> getFormKeywordsPos(PdfDocument doc) {
        int pages = doc.getNumberOfPages();
        Map<Integer, Map<String, float[]>> maps = new HashMap<>(pages);
        for (int index = 1; index <= pages; index++) {
            maps.putIfAbsent(index, new HashMap<>());
            PdfPage page = doc.getPage(index);
            // 获取当前页的表单域
            int finalIndex = index;
            page.getAnnotations().forEach(anno -> {
                PdfString title = anno.getTitle();
                PdfArray rectangle = anno.getRectangle();
                float x = rectangle.getAsNumber(0).floatValue();
                float y = rectangle.getAsNumber(1).floatValue();
                float width = rectangle.getAsNumber(2).floatValue() - x;
                float height = rectangle.getAsNumber(3).floatValue() - y;
                maps.get(finalIndex).put(title.getValue(), new float[]{x, y, width, height});
            });
        }
        return maps;
    }

    private Pdf7TemplateFillUtil(PdfReader template) {
        this.template = template;
    }

    public static Pdf7TemplateFillUtil load(String template) throws IOException {
        return new Pdf7TemplateFillUtil(new PdfReader(template));
    }

    public static Pdf7TemplateFillUtil load(File template) throws IOException {
        return new Pdf7TemplateFillUtil(new PdfReader(template));
    }

    public static Pdf7TemplateFillUtil load(byte[] template) throws IOException {
        return new Pdf7TemplateFillUtil(new PdfReader(new ByteArrayInputStream(template)));
    }

    public static Pdf7TemplateFillUtil load(InputStream template) throws IOException {
        return new Pdf7TemplateFillUtil(new PdfReader(template));
    }

    static class PageNumberEvent implements IEventHandler {
        private transient final PdfFont font;
        private transient final boolean firstPageNo;

        PageNumberEvent(PdfFont font, boolean firstPageNo) {
            this.font = font;
            this.firstPageNo = firstPageNo;
        }

        @Override
        public void handleEvent(Event event) {
            PdfDocumentEvent docEvent = (PdfDocumentEvent) event;
            PdfDocument pdf = docEvent.getDocument();
            PdfPage page = docEvent.getPage();
            int pageNumber = pdf.getPageNumber(page);
            pageNumber = firstPageNo ? pageNumber : pageNumber - 1;
            if (pageNumber > 0) {
                Rectangle pageSize = page.getPageSize();
                PdfCanvas pdfCanvas = new PdfCanvas(page.getLastContentStream(), page.getResources(), pdf);
                Canvas canvas = new Canvas(pdfCanvas, pageSize);
                float x = (pageSize.getLeft() + pageSize.getRight()) / 2;
                float y = pageSize.getBottom() + 10;
                Paragraph p = new Paragraph(String.valueOf(pageNumber))
                        .setFontSize(10)
                        .setFont(font);
                canvas.showTextAligned(p, x, y, TextAlignment.CENTER);
                canvas.close();
            }
        }
    }
}

特别注意

字体加载有一个巨坑，一定要放在具体的方法中去加载，保证用完即销毁。

否则填充时会出错：Pdf indirect object belongs to other PDF document....