<dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>4.1.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>4.1.2</version>
        </dependency>
        <dependency>
            <groupId>org.jsoup</groupId>
            <artifactId>jsoup</artifactId>
            <version>1.14.3</version>
        </dependency>

import org.apache.poi.xwpf.usermodel.XWPFDocument;
import org.apache.poi.xwpf.usermodel.XWPFParagraph;
import org.apache.poi.xwpf.usermodel.XWPFRun;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;

public class HtmlToDocxConverter {
    public static void main(String[] args) {
        File file = new File("C:\\temp\\test.docx");
        try {
            FileInputStream fis = new FileInputStream(file);
            XWPFDocument xdoc = new XWPFDocument(fis);
            String key = "遗嘱";
            String color = "ff0000";
            int size = xdoc.getParagraphs().size();
            for (int i1 = 0; i1 < size; i1++) {
                XWPFParagraph paragraph = xdoc.createParagraph();
                String end = generator(paragraph,key,color, xdoc.getParagraphs().get(i1).getText());
                paragraph.createRun().setText(end);
            }
            for (int j = 0; j < size; j++) {
                xdoc.removeBodyElement(0);
            }

            OutputStream os= new FileOutputStream("C:\\temp\\test2.docx");
            xdoc.write(os);
            fis.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static String generator(XWPFParagraph paragraph,String key,String color,String s) {
        String end = splitStr(s,key);
        if (s.contains(key)) {
            String begin = "";
            // ---------- 拆分段落为：前，关键字，后 三个run ----------
            begin = s.substring(0, s.indexOf(key));                // 取出段落中关键字之前的内容
            paragraph.createRun().setText(begin);
            XWPFRun run = paragraph.createRun();
            run.setText(key);
            run.setColor(color);
            return generator(paragraph,key,color,end);
        } else {
            return end;
        }
    }

    private static String splitStr(String content,String key) {
        if (content.contains(key)) {
            return content.substring(content.indexOf(key) + key.length());
        } else {
            return content;
        }
    }
}