教你怎么用Java通过关键字修改pdf

import com.itextpdf.text.Chunk;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Font;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.BaseFont;
import com.itextpdf.text.pdf.ColumnText;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFORMat;
import java.util.Date;
import java.util.UUID;


public class UpdatePdf {

    public static void main(String[] args) {
        File file = new File("G://files//cs//111.pdf");//模拟文件位置
        if(file!=null && file.exists()){
            FileInputStream is = null;
            try {
                //本地根据文件路径获取文件流
                is = new FileInputStream(file);
                long length = file.length();
                byte[] fileBytes = new byte[(int)length];
                is.read(fileBytes);
                //进行pdf文件修改
                File file1 = pdfFzSqsj(fileBytes);
                if(file1!=null && file1.exists()){
                    System.out.println("修改pdf完成！");
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if(is!=null){
                    try {
                        is.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    
    private static File pdfFzSqsj(byte[] tpeHtcxyw) {
        PdfStamper stamper = null;
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");
            //获取要写入的申请时间
            String sj  =sdf.format(new Date());
            PdfReader reader = new PdfReader(tpeHtcxyw);
            //创建文件路径
			String filePath = "G://files/cs/";
            System.out.println("filePath="+filePath);
            File directory = new File(filePath);
            //如果pdf保存路径不存在，则创建路径
            if (!directory.exists()) {
                directory.mkdirs();
            }
            String filename = UUID.randomUUID()+"_after.pdf";//修改后文件
			String filename1 = UUID.randomUUID()+"_before.pdf";//修改前文件 再输出一遍，校验自己在修改之前拿到正确的文件流
            System.out.println("file:"+filePath+filename);
            File file = new File(filePath+filename);
			File file1 = new File(filePath+filename1);
            //将写入临时文件
			FileOutputStream  foss = new FileOutputStream (file1);
			foss.write(tpeHtcxyw);
			foss.close();
            //设置字体
            BaseFont baseFont = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", false);
            Font font = new Font(baseFont);
            stamper = new PdfStamper(reader, new FileOutputStream(file));
            //对于已经固话的pdf回填申请时间
            for (int i = 1; i <= reader.getNumberOfPages(); i++) {
                PdfContentByte over = stamper.getOverContent(i);
                ColumnText columnText = new ColumnText(over);
                if(i==1){
                    String str = "申请日期：";
                    //根据关键字获取关键字位置
                    float[] po =  Html2Pdf.getGzzzb(str,tpeHtcxyw);
                    if(po[0]==1.00f){
                        // 方法setSimpleColumn(float llx, float lly, float urx, float ury)
                        // llx 和 urx  最小的值决定离左边的距离. lly 和 ury 最大的值决定离下边的距离
                        columnText.setSimpleColumn( po[1]+46f,  po[2]-9f, 500, 0);
                        //将时间文本创建成对象
                        Paragraph elements = new Paragraph(0, new Chunk(new Chunk(sj)));
                        // 设置字体，如果不设置添加的中文将无法显示
                        elements.setFont(font);
                        columnText.addElement(elements);
                        columnText.Go();
                    }
                }
            }
            return file;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if(stamper!=null){
                try {
                    stamper.close();
                } catch (DocumentException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import com.itextpdf.awt.geom.Rectangle2D;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.parser.ImageRenderInfo;
import com.itextpdf.text.pdf.parser.PdfReaderContentParser;
import com.itextpdf.text.pdf.parser.RenderListener;
import com.itextpdf.text.pdf.parser.TextRenderInfo;

public class Html2Pdf {
    
    public static float[] getGzzzb(String signKey, byte[] pdf){
        PdfReader reader=null;
        final float[] po = new float[3];
        try{
            reader = new PdfReader(pdf);
            int pageNum = reader.getNumberOfPages();
            final String signKeyWord = signKey;
            for(int page=1; page <= pageNum; page++){
                PdfReaderContentParser pdfReaderContentParser = new PdfReaderContentParser(reader);
                pdfReaderContentParser.processContent(page, new RenderListener() {
                    StringBuilder sb = new StringBuilder("");
                    int maxLength = signKeyWord.length();
                    @Override
                    public void renderText(TextRenderInfo textRenderInfo) {
                        // 只适用 单字块文档 以及 关键字整个为一个块的情况
                        // 设置 关键字文本为单独的块，不然会错位
                        boolean isKeywordChunk = textRenderInfo.getText().length() == maxLength;
                        if (isKeywordChunk) {
                            // 文档按照 块 读取
                            sb.delete(0, sb.length());
                            sb.append(textRenderInfo.getText());
                        } else {
                            // 有些文档 单字一个块的情况
                            // 拼接字符串
                            sb.append(textRenderInfo.getText());
                            // 去除首部字符串，使长度等于关键字长度
                            if (sb.length() > maxLength) {
                                sb.delete(0, sb.length() - maxLength);
                            }
                        }
                        // 判断是否匹配上
                        if (signKeyWord.equals(sb.toString())) {
                            // 计算中心点坐标
                            Rectangle2D.Float baseFloat = textRenderInfo.getBaseline()
                                    .getBoundingRectange();
                            Rectangle2D.Float ascentFloat = textRenderInfo.getAscentLine()
                                    .getBoundingRectange();
                            float centreX;
                            float centreY;
                            if (isKeywordChunk) {
                                centreX = baseFloat.x + 5*ascentFloat.width / 6;
                                centreY = baseFloat.y + (5*(ascentFloat.y - baseFloat.y) / 6);
                            } else {
                                centreX = baseFloat.x + ascentFloat.width - (5*maxLength * ascentFloat.width / 6);
                                centreY = baseFloat.y + (5*(ascentFloat.y - baseFloat.y) / 6);
                            }
                            po[0]=1.00f;
                            po[1]=centreX+3;
                            po[2]=centreY;
                            // 匹配完后 清除
                            sb.delete(0, sb.length());
                        }
                    }
                    @Override
                    public void renderImage(ImageRenderInfo arg0) {}
                    @Override
                    public void endTextBlock() {}
                    @Override
                    public void beginTextBlock() {}
                });
            }
            if(po[0]==1.00f){
                return po;
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally {
            if(reader!=null){
                reader.close();
            }
        }
        return null;
    }