Java实现LaTeX转为OMML并写入word文档_Java

1.需求

我有一些数学考题试卷数据存在数据库，考题数据是以大文本的形式存储，其中公式部分的格式为latex，现在需要将这些数据生成word文档供用户下载，要求公式能够正确在文档中显示，一种方案是将latex转换成图片，然后写入word文档，缺点是清晰度不高，而且不可编辑。所以需要一个原生的解决方案，自然就想到word对latex的支持，遗憾的是word不支持latex, 而是有自己的格式omml, 所以需要一个工具来将latex转换成omml，现有的资料显示需要先将latex转换成mathml，然后将mathml转换成omml。

2.代码结构

3.pom文件

<?xml version="1.0" encoding="utf-8"?>
<project xmlns="http://maven.apache.org/pom/4.0.0" xmlns:xsi="http://www.w3.org/2001/xmlschema-instance"
         xsi:schemalocation="http://maven.apache.org/pom/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelversion>4.0.0</modelversion>
    <parent>
        <groupid>org.springframework.boot</groupid>
        <artifactid>spring-boot-starter-parent</artifactid>
        <version>2.5.8</version>
        <relativepath/>
    </parent>
    <groupid>com.latex</groupid>
    <artifactid>latex</artifactid>
    <version>1.0.0</version>
    <name>latex</name>
    <description>latex</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupid>org.springframework.boot</groupid>
            <artifactid>spring-boot-starter</artifactid>
        </dependency>
        <dependency>
            <groupid>org.projectlombok</groupid>
            <artifactid>lombok</artifactid>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupid>org.springframework.boot</groupid>
            <artifactid>spring-boot-starter-test</artifactid>
            <scope>test</scope>
        </dependency>
        <!-- 以下为转换和word操作需要的依赖 -->
        <dependency>
            <groupid>de.rototor.snuggletex</groupid>
            <artifactid>snuggletex-core</artifactid>
            <version>1.3.0</version>
        </dependency>
        <dependency>
            <groupid>org.apache.poi</groupid>
            <artifactid>poi</artifactid>
            <version>4.1.2</version>
        </dependency>
        <dependency>
            <groupid>org.apache.poi</groupid>
            <artifactid>ooxml-schemas</artifactid>
            <version>1.4</version>
        </dependency>
        <dependency>
            <groupid>org.apache.poi</groupid>
            <artifactid>poi-ooxml</artifactid>
            <version>4.1.2</version>
        </dependency>
        <dependency>
            <groupid>commons-io</groupid>
            <artifactid>commons-io</artifactid>
            <version>2.11.0</version>
        </dependency>
    </dependencies>
    <build>
        <!--
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
                <includes>
                    <include>mml2omml.xsl</include>
                </includes>
            </resource>
        </resources>
        -->
        <plugins>
            <plugin>
                <groupid>org.apache.maven.plugins</groupid>
                <artifactid>maven-compiler-plugin</artifactid>
                <configuration>
                    <annotationprocessorpaths>
                        <path>
                            <groupid>org.projectlombok</groupid>
                            <artifactid>lombok</artifactid>
                        </path>
                    </annotationprocessorpaths>
                </configuration>
            </plugin>
            <plugin>
                <groupid>org.springframework.boot</groupid>
                <artifactid>spring-boot-maven-plugin</artifactid>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupid>org.projectlombok</groupid>
                            <artifactid>lombok</artifactid>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

4.转换工具：latexutil

package com.latex.util;

import com.latex.enums.textcircledenum;
import org.apache.poi.xwpf.usermodel.xwpfparagraph;
import org.apache.xmlbeans.xmlcursor;
import org.apache.xmlbeans.xmlexception;
import org.openxmlformats.schemas.officedocument.x2006.math.ctomath;
import org.openxmlformats.schemas.officedocument.x2006.math.ctomathpara;
import org.openxmlformats.schemas.officedocument.x2006.math.ctr;
import uk.ac.ed.ph.snuggletex.snuggleengine;
import uk.ac.ed.ph.snuggletex.snuggleinput;
import uk.ac.ed.ph.snuggletex.snugglesession;

import javax.xml.transform.transformer;
import javax.xml.transform.transformerexception;
import javax.xml.transform.transformerfactory;
import javax.xml.transform.stream.streamresult;
import javax.xml.transform.stream.streamsource;
import java.io.ioexception;
import java.io.inputstream;
import java.io.stringreader;
import java.io.stringwriter;

public class latexutil {
    private static transformer transformer;
    private static final snuggleengine snuggleengine =  new snuggleengine();

    /**
     * 将latex公式添加到poi段落中
     * @param paragraph 段落
     * @param latex 公式
     */
    public static void addtoparagraph(xwpfparagraph paragraph, string latex) throws exception{
        latex = "$" + filter(latex) + "$"; //处理特殊符号
        paragraph.getctp().addnewomath().set(getctomath(latex));
    }

    /**
     * 将latex公式转换成ctomath（可直接写入word）
     * @param latex 公式
     * 这里的latex表达式 必须用$$包裹，例如：$\sin^2 \theta + \cos^2 \theta = 1$
     */
    public static ctomath getctomath(string latex) throws exception {
        system.out.println("latex: " + latex);
        string mathml = tomathml(latex);
        system.out.println("mathml: " + mathml);
        string omml = toomml(mathml);
        system.out.println("omml: " + omml);
        return toctomath(omml);
    }

    /**
     * latex转mathml
     */
    public static string tomathml(string latex) throws ioexception {
        snugglesession session = snuggleengine.createsession();
        session.parseinput(new snuggleinput(latex));
        return session.buildxmlstring();
    }

    /**
     * mathml转omml
     */
    public static string toomml(string mathml) throws transformerexception, ioexception {
        transformer transformer = gettransformer();
        streamsource source = new streamsource(new stringreader(mathml));
        stringwriter stringwriter = new stringwriter();
        streamresult result = new streamresult(stringwriter);
        transformer.transform(source, result);
        string omml = stringwriter.tostring();
        stringwriter.close();
        return omml;
    }

    /**
     * 基于omml创建poi组件：ctomath
     */
    public static ctomath toctomath(string omml) throws xmlexception {
        ctomathpara ctomathpara = ctomathpara.factory.parse(omml);
        ctomath ctomath = ctomathpara.getomatharray(0);
        //for making this to work with office 2007 word also, special font settings are necessary
        xmlcursor xmlcursor = ctomath.newcursor();
        while (xmlcursor.hasnexttoken()) {
            xmlcursor.tokentype tokentype = xmlcursor.tonexttoken();
            if (tokentype.isstart()) {
                if (xmlcursor.getobject() instanceof ctr) {
                    ctr ctr = (ctr) xmlcursor.getobject();
                    ctr.addnewrpr2().addnewrfonts().setascii("cambria math");
                    ctr.getrpr2().getrfonts().sethansi("cambria math"); // up to apache poi 4.1.2
                    //ctr.getrpr2().getrfontsarray(0).sethansi("cambria math"); // since apache poi 5.0.0
                }
            }
        }
        return ctomath;
    }

    /**
     * 发现存在无法识别的符号，因此单独处理，提前过滤识别掉
     * ①②③④⑤等符合无法识别，即latex表达式是 \textcircled
     * @param latex latex表达式
     * @return 处理结果
     */
    public static string filter(string latex){
        if(!latex.contains("textcircled")){
            return latex;
        }
        return textcircledenum.replacetextcircled(latex);
    }

    private static transformer gettransformer() throws transformerexception {
        if(transformer == null){
            //实测发现jdk21需要修改以下配置，不然newtransformer会报错：
            //javax.xml.transform.transformerconfigurationexception: jaxp0801001
            //system.setproperty("jdk.xml.xpathexprgrplimit", "0"); // 0表示无限制
            //system.setproperty("jdk.xml.xpathexproplimit", "0");  // 同时设置操作符限制

            //如果读取不到mml2omml.xsl文件，请检查pom文件
            //build->resources->resource->includes下添加：<include>mml2omml.xsl</include>
            inputstream in = latexutil.class.getclassloader().getresourceasstream("mml2omml.xsl");
            transformerfactory tfactory = transformerfactory.newinstance();
            transformer = tfactory.newtransformer(new streamsource(in));
        }
        return transformer;
    }
}

5.特殊符号处理：textcircledenum

package com.latex.enums;

import lombok.allargsconstructor;
import lombok.getter;

@getter
@allargsconstructor
public enum textcircledenum {
    zero("\\\\textcircled\\{0\\}","⓪"),
    one("\\\\textcircled\\{1\\}","①"),
    two("\\\\textcircled\\{2\\}","②"),
    three("\\\\textcircled\\{3\\}","③"),
    four("\\\\textcircled\\{4\\}","④"),
    five("\\\\textcircled\\{5\\}","⑤"),
    six("\\\\textcircled\\{6\\}","⑥"),
    seven("\\\\textcircled\\{7\\}","⑦"),
    eight("\\\\textcircled\\{8\\}","⑧"),
    nine("\\\\textcircled\\{9\\}","⑨"),
    ten("\\\\textcircled\\{10\\}","⑩");

    private final string code;
    private final string value;

    public static string replacetextcircled(string latex){
        for (textcircledenum c : values()) {
            latex = latex.replaceall(c.getcode(), c.getvalue());
        }
        return latex;
    }
}

6.测试类：latexutiltest

package com.latex.test;

import com.latex.util.latexutil;
import org.apache.poi.xwpf.usermodel.paragraphalignment;
import org.apache.poi.xwpf.usermodel.xwpfdocument;
import org.apache.poi.xwpf.usermodel.xwpfparagraph;

import java.io.fileoutputstream;

public class latexutiltest {
    public static void main(string[] args) throws exception {
        xwpfdocument document = new xwpfdocument();
        xwpfparagraph paragraph = document.createparagraph();
        paragraph.setalignment(paragraphalignment.left);
        paragraph.setfontalignment(paragraphalignment.left.getvalue());

        paragraph.createrun().settext("前置文本：");
        latexutil.addtoparagraph(paragraph, "\\sin^2 \\theta + \\cos^2 \\theta = 1");
        paragraph.createrun().settext("后置文本");


        // 保存文档到文件
        string filepath = "d:\\test\\math_document_"+system.currenttimemillis()+".docx";
        try (fileoutputstream out = new fileoutputstream(filepath)) {
            document.write(out);
            system.out.println("word文档已成功保存");
        }

        // 关闭文档
        document.close();
    }
}

7.测试输出

latex: $\sin^2 \theta + \cos^2 \theta = 1$
mathml: <math xmlns="http://www.w3.org/1998/math/mathml"><msup><mi>sin</mi><mn>2</mn></msup><mi>θ</mi><mo>+</mo><msup><mi>cos</mi><mn>2</mn></msup><mi>θ</mi><mo>=</mo><mn>1</mn></math>
omml: <?xml version="1.0" encoding="utf-8"?><m:omath xmlns:m="http://schemas.openxmlformats.org/officedocument/2006/math" xmlns:mml="http://www.w3.org/1998/math/mathml"><m:ssup><m:e><m:r><m:rpr><m:sty m:val="p"/></m:rpr><m:t>sin</m:t></m:r></m:e><m:sup><m:r><m:t>2</m:t></m:r></m:sup></m:ssup><m:r><m:t>θ</m:t></m:r><m:r><m:t>+</m:t></m:r><m:ssup><m:e><m:r><m:rpr><m:sty m:val="p"/></m:rpr><m:t>cos</m:t></m:r></m:e><m:sup><m:r><m:t>2</m:t></m:r></m:sup></m:ssup><m:r><m:t>θ</m:t></m:r><m:r><m:t>=</m:t></m:r><m:r><m:t>1</m:t></m:r></m:omath>
word文档已成功保存