新需求需要写程序在word中插入Latex公式。所以研究了一下JavaPOI库。本文章记录一下坑。

首先现在的docx文件中的公式使用的是OMML,Latex公式不能直接插入，需要先转换成MathML再转成OMML。

其中MathML to OMML这一部分已经有微软现成的XSL样式表MML2OMML.XSL 只要你安装了新office，就能在目录中搜到这个文件。

SnuggleTeX 这个java库可以实现Latex字符串转MathML，所以思路比较明确，就是先用SnuggleTeX转MathML,再用MML2OMML转成OOMML，插入到段落中。

下面是代码：

public class main{
    static File stylesheet = new File("MML2OMML.XSL");
    static TransformerFactory tFactory = TransformerFactory.newInstance();
    static StreamSource styleSource = new StreamSource(stylesheet);

    public static CTOMath _getOMML(String mathML) throws Exception {
        Transformer transformer = tFactory.newTransformer(styleSource);
        StringReader stringreader = new StringReader(mathML);
        StreamSource source = new StreamSource(stringreader);
        StringWriter stringwriter = new StringWriter();
        StreamResult result = new StreamResult(stringwriter);
        transformer.transform(source, result);
        String ooML = stringwriter.toString();
        stringwriter.close();

        CTOMathPara ctOMathPara = CTOMathPara.Factory.parse(ooML);
        CTOMath ctOMath = ctOMathPara.getOMathArray(0);
        XmlCursor xmlcursor = ctOMath.newCursor();
        while (xmlcursor.hasNextToken()) {
            XmlCursor.TokenType tokentype = xmlcursor.toNextToken();
            if (tokentype.isStart()) {
                if (xmlcursor.getObject() instanceof CTR cTR) {
                    cTR.addNewRPr2().addNewRFonts().setAscii("Cambria Math");
                    cTR.getRPr2().getRFontsArray(0).setHAnsi("Cambria Math");
                }
            }
        }
        return ctOMath;
    }
    public void add_latex(String latex,XWPFParagraph paragraph) throws Exception {
        SnuggleEngine engine = new SnuggleEngine();
        SnuggleSession session = engine.createSession();
        SnuggleInput input = new SnuggleInput(latex);
        session.parseInput(input);
        String mathML = session.buildXMLString();
        CTOMath ctOMath = _getOMML(mathML);
        CTP ctp = paragraph.getCTP();
        ctp.setOMathArray(new CTOMath[]{ctOMath});
    }

}

QA:

JAXP0801001: the compiler encountered an XPath expression containing '11' groups that exceeds the '10' limit set by 'FEATURE_SECURE_PROCESSING'.

解决方式：修改VM选项。添加 -Djdk.xml.xpathExprGrpLimit=0 -Djdk.xml.xpathExprOpLimit=0 -Djdk.xml.xpathTotalOpLimit=0

参考链接：https://stackoverflow.com/questions/46623554/add-latex-type-equation-in-word-docx-using-apache-poi/46628613#46628613