一、下载依赖
采用免费的POI来实现Word字数统计和添加水印。
1.1、在项目依赖中添加

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

二、工具类(WordUtils)

 package com.gientech.jep.service.sys.util;

import com.microsoft.schemas.office.office.CTLock;
import com.microsoft.schemas.vml.*;
mport org.apache.poi.wp.usermodel.*;
import org.apache.poi.xwpf.model.XWPFHeaderFooterPolicy;
import org.apache.poi.xwpf.usermodel.XWPFDocument;
import org.apache.poi.xwpf.usermodel.XWPFHeader;
import org.apache.poi.xwpf.usermodel.XWPFParagraph;
import org.apache.poi.xwpf.usermodel.XWPFRun;
import org.openxmlformats.schemas.wordprocessingml.x2006.main.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.*;
import java.util.List;
import java.util.stream.Stream;

/**
 * word 工具处理类
 * @author houyinke
 * @date 2022/7/19 15:57
 */
public class WordUtils {

static Logger logger = LoggerFactory.getLogger(WordUtils.class);

/**
 * 水印字体字体
 */
private static final String fontName = "PingFang SC";

/**
 *  一个字平均长度，单位pt，用于：计算文本占用的长度（文本总个数*单字长度）
 */
private static final int widthPerWord = 10;

/**
 * word文字水印(调用poi封装的createWatermark方法)
 * @param doc XWPFDocument对象
 * @param markStr 水印文字
 */
public static void setWordWaterMark(XWPFDocument doc, String markStr,String fontColor) {
    XWPFParagraph paragraph = doc.createParagraph();
    XWPFHeaderFooterPolicy headerFooterPolicy = doc.getHeaderFooterPolicy();
    if (headerFooterPolicy == null) {
        headerFooterPolicy = doc.createHeaderFooterPolicy();
    }
    // create default Watermark - fill color black and not rotated
    headerFooterPolicy.createWatermark(markStr);
    // get the default header
    // Note: createWatermark also sets FIRST and EVEN headers
    // but this code does not updating those other headers
    XWPFHeader header = headerFooterPolicy.getHeader(XWPFHeaderFooterPolicy.DEFAULT);
    paragraph = header.getParagraphArray(0);
//            // get com.microsoft.schemas.vml.CTShape where fill color and rotation is set
    paragraph.getCTP().newCursor();
    org.apache.xmlbeans.XmlObject[] xmlobjects = paragraph.getCTP().getRArray(0).getPictArray(0).selectChildren(
            new javax.xml.namespace.QName("urn:schemas-microsoft-com:vml", "shape"));
    if (xmlobjects.length > 0) {
        CTShape ctshape = (CTShape) xmlobjects[0];
        ctshape.setFillcolor(fontColor);
        ctshape.setStyle(ctshape.getStyle() + ";rotation:315");
    }
}

/**
 * 将指定的字符串重复repeats次.
 * @param pattern 字符串
 * @param repeats 重复次数
 * @return 生成的字符串
 */
private static String repeatString(String pattern, int repeats) {
    StringBuilder buffer = new StringBuilder(pattern.length() * repeats);
    Stream.generate(() -> pattern).limit(repeats).forEach(buffer::append);
    return new String(buffer);
}

/**
 * 为文档添加水印
 * 实现参考了{@link XWPFHeaderFooterPolicy#(String, int)}
 * @param doc 需要被处理的docx文档对象
 * @param customText 水印文本
 * @param type 类型：1.平铺；2.单个
 */
private static void waterMarkDocXDocument(XWPFDocument doc, String customText, String styleTop, int type,String fontColor,String fontSize,String rotation) {
    XWPFHeader header = doc.createHeader(HeaderFooterType.DEFAULT); // 如果之前已经创建过 DEFAULT 的Header，将会复用之
    int size = header.getParagraphs().size();
    if (size == 0) {
        header.createParagraph();
    }

    CTP ctp = header.getParagraphArray(0).getCTP();
    byte[] rsidr = doc.getDocument().getBody().getPArray(0).getRsidR();
    byte[] rsidrdefault = doc.getDocument().getBody().getPArray(0).getRsidRDefault();
    ctp.setRsidP(rsidr);
    ctp.setRsidRDefault(rsidrdefault);
    CTPPr ppr = ctp.addNewPPr();
    ppr.addNewPStyle().setVal("Header");

    // 开始加水印
    CTR ctr = ctp.addNewR();
    CTRPr ctrpr = ctr.addNewRPr();
    ctrpr.addNewNoProof();
    CTGroup group = CTGroup.Factory.newInstance();
    CTShapetype shapetype = group.addNewShapetype();
    CTTextPath shapeTypeTextPath = shapetype.addNewTextpath();
    shapeTypeTextPath.setOn(STTrueFalse.T);
    shapeTypeTextPath.setFitshape(STTrueFalse.T);
    CTLock lock = shapetype.addNewLock();
    lock.setExt(STExt.VIEW);
    CTShape shape = group.addNewShape();
    shape.setId("PowerPlusWaterMarkObject");
    shape.setSpid("_x0000_s102");
    shape.setType("#_x0000_t136");

    // 平铺或单个
    if(type != 2){
        // 设置形状样式（旋转，位置，相对路径等参数）
        shape.setStyle(getShapeStyle(customText, styleTop,rotation));
    }else{
        // 设置形状样式（旋转，位置，相对路径等参数）
        shape.setStyle(getShapeStyle());
    }

    shape.setFillcolor(fontColor);
    // 字体设置为实心
    shape.setStroked(STTrueFalse.FALSE);
    // 绘制文本的路径
    CTTextPath shapeTextPath = shape.addNewTextpath();
    // 设置文本字体与大小
    shapeTextPath.setStyle("font-family:" + fontName + ";font-size:" + fontSize);
    shapeTextPath.setString(customText);
    CTPicture pict = ctr.addNewPict();
    pict.set(group);
}

/**
 * 以艺术字方式加上水印(平铺)
 * @param docx XWPFDocument对象
 * @param customText 水印文字
 */
public static void makeFullWaterMarkByWordArt(XWPFDocument docx, String customText,String fontColor,String fontSize,String styleRotation) {
    // 水印文字之间使用8个空格分隔
    customText = customText + repeatString(" ", 16);
    // 一行水印重复水印文字次数
    customText = repeatString(customText, 10);
    // 与顶部的间距
    String styleTop = "0pt";

    if (docx == null) {
        return;
    }

    // 遍历文档，添加水印
    for (int lineIndex = -10; lineIndex < 20; lineIndex++) {
        styleTop = 200 * lineIndex + "pt";
        waterMarkDocXDocument(docx, customText, styleTop, 1,fontColor, fontSize ,styleRotation);
    }
}

/**
 * 以艺术字方式加上水印(单个)
 * @param docx XWPFDocument对象
 * @param customText 水印文字
 */
public static void makeWaterMarkByWordArt(XWPFDocument docx, String customText,String fontColor,String fontSize,String rotation) {
    // 与顶部的间距
    String styleTop = "0pt";
    // 判断文档是否为空
    if (docx == null) {
        return;
    }

    // 添加水印
    waterMarkDocXDocument(docx, customText, styleTop, 2,fontColor,fontSize,rotation);
}

/**
 * 构建Shape的样式参数
 * @param customText 水印文本
 * @return
 */
private static String getShapeStyle(String customText, String styleTop,String styleRotation) {
    StringBuilder sb = new StringBuilder();
    // 文本path绘制的定位方式
    sb.append("position: ").append("absolute");
    // 计算文本占用的长度（文本总个数*单字长度）
    sb.append(";width: ").append(customText.length() * widthPerWord).append("pt");
    // 字体高度
    sb.append(";height: ").append("20pt");
    sb.append(";z-index: ").append("-251654144");
    sb.append(";mso-wrap-edited: ").append("f");
    sb.append(";margin-top: ").append(styleTop);
    sb.append(";mso-position-horizontal-relative: ").append("margin");
    sb.append(";mso-position-vertical-relative: ").append("margin");
    sb.append(";mso-position-vertical: ").append("left");
    sb.append(";mso-position-horizontal: ").append("center");
    sb.append(";rotation: ").append(styleRotation);
    return sb.toString();
}

/**
 * 构建Shape的样式参数
 * @return
 */
private static String getShapeStyle() {
    StringBuilder sb = new StringBuilder();
    // 文本path绘制的定位方式
    sb.append("position: ").append("absolute");
    sb.append(";left: ").append("opt");
    // 计算文本占用的长度（文本总个数*单字长度）
    sb.append(";width: ").append("500pt");
    // 字体高度
    sb.append(";height: ").append("150pt");
    sb.append(";z-index: ").append("-251654144");
    sb.append(";mso-wrap-edited: ").append("f");
    sb.append(";margin-left: ").append("-50pt");
    sb.append(";margin-top: ").append("270pt");
    sb.append(";mso-position-horizontal-relative: ").append("margin");
    sb.append(";mso-position-vertical-relative: ").append("margin");
    sb.append(";mso-width-relative: ").append("page");
    sb.append(";mso-height-relative: ").append("page");
    sb.append(";rotation: ").append("-2949120f");
    return sb.toString();
}

/**
 * word 字数统计
 * @param xwpfDocument doc文档
 * @return
 */
public static int count(XWPFDocument xwpfDocument){
    List<XWPFParagraph> paragraphs = xwpfDocument.getParagraphs();
    // 行数,字数
    int rowCount = 1, count = 0;

    try {
        // 循环读取字数
        for (XWPFParagraph xwpfParagraph : paragraphs) {
            int linLength = 0;
            String lineStr = "";
            List<XWPFRun> xwpfRuns = xwpfParagraph.getRuns();
            for (XWPFRun xwpfRun : xwpfRuns) {
                linLength += xwpfRun.toString().trim().length();
                lineStr += xwpfRun.toString();
                count += xwpfRun.toString().trim().length();
            }

            logger.info("第" + rowCount + "行内容,长度：" + linLength);
            rowCount ++;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

    return count;
}

/**
 * 加载docx格式的word文档
 * @param inputStream
 * @return
 */
private static XWPFDocument loadDocXDocument(InputStream inputStream) {
    XWPFDocument doc;
    try {
        doc = new XWPFDocument(inputStream);
    } catch (Exception e) {
        throw new RuntimeException("文档加载失败！！");
    }
    return doc;
}

public static void main(String[] args) throws IOException {
    XWPFDocument xwpfDocument = null;
    try {
        //输入的docx文档
        InputStream in = new FileInputStream(new File("/Users/houyinke/Desktop/doc/4.doc"));
        xwpfDocument = WordUtils.loadDocXDocument(in);

        // 统计字数
        int count = WordUtils.count(xwpfDocument);
        System.out.println("word字数：" + count);

        // 添加水印
        WordUtils.makeFullWaterMarkByWordArt(xwpfDocument, "中电金信", "#888888", "0.7pt","-30");

        // 写出加水印后的文档
        String filePath = "/Users/houyinke/Desktop/doc/3.docx";
        OutputStream os = new FileOutputStream(filePath);
        xwpfDocument.write(os);
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if(xwpfDocument != null){
            xwpfDocument.close();
        }
    }
}

}