可不可以不生成新的行，直接插入到占位符的位置上

是可以的。如果您已经在 Word 文档中创建了一个占位符，您可以使用以下代码将图片插入到该占位符的位置上：

private static void insertPictureInPlaceholder(String placeholderText, InputStream pictureData, int format, XWPFDocument document) {
    for (XWPFParagraph paragraph : document.getParagraphs()) {
        for (XWPFRun run : paragraph.getRuns()) {
            String text = run.getText(0);
            if (text != null && text.contains(placeholderText)) {
                try {
                    String blipId = document.addPictureData(pictureData, format);
                    int id = document.getAllPictures().size() - 1;
                    CTR ctr = run.getCTR();
                    CTInline inline = ctr.addNewDrawing().addNewInline();
                    String picXml = "<a:graphic xmlns:a=\"http://schemas.openxmlformats.org/drawingml/2006/main\">" +
                            "   <a:graphicData uri=\"http://schemas.openxmlformats.org/drawingml/2006/picture\">" +
                            "      <pic:pic xmlns:pic=\"http://schemas.openxmlformats.org/drawingml/2006/picture\">" +
                            "         <pic:nvPicPr>" +
                            "            <pic:cNvPr id=\"" + id + "\" name=\"Generated\"/>" +
                            "            <pic:cNvPicPr/>" +
                            "         </pic:nvPicPr>" +
                            "         <pic:blipFill>" +
                            "            <a:blip r:embed=\"" + blipId + "\" xmlns:r=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships\"/>" +
                            "            <a:stretch>" +
                            "               <a:fillRect/>" +
                            "            </a:stretch>" +
                            "         </pic:blipFill>" +
                            "         <pic:spPr>" +
                            "            <a:xfrm>" +
                            "               <a:off x=\"0\" y=\"0\"/>" +
                            "               <a:ext cx=\"5000000\" cy=\"5000000\"/>" +
                            "            </a:xfrm>" +
                            "            <a:prstGeom prst=\"rect\">" +
                            "               <a:avLst/>" +
                            "            </a:prstGeom>" +
                            "         </pic:spPr>" +
                            "      </pic:pic>" +
                            "   </a:graphicData>" +
                            "</a:graphic>";
                    inline.addNewGraphic().addNewGraphicData();
                    XmlToken xmlToken = null;
                    try {
                        xmlToken = XmlToken.Factory.parse(picXml);
                    } catch (XmlException xe) {
                        xe.printStackTrace();
                    }
                    inline.set(xmlToken);
                    CTDrawing ctDrawing = inline.getDrawingArray(0);
                    ctDrawing.setAnchorArray(new CTDrawing.Anchor[]{});
                    run.setText(text.replace(placeholderText, ""), 0);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

这里，我们遍历了 Word 文档中的所有段落和行，找到包含占位符文本的行。然后，我们插入了图片，并将其添加到与占位符文本相同的行中，最后用占位符文本替换了原始文本。这样，图片就会出现在占位符的位置上。