一步一步将PlantUML类图导出为自定义格式的XMI文件

说明：

• 首次发表日期：2024-09-08
• PlantUML官网： https://plantuml.com/zh/
• PlantUML命令行文档： https://plantuml.com/zh/command-line#6a26f548831e6a8c
• PlantUML XMI文档: https://plantuml.com/zh/xmi
• 进一步用处：根据导出的XMI文件生成代码

PlantUML（Java）中获取类图以及plantuml xmi代码是如何遍历实体并获取属性的

以下是来自 https://stackoverflow.com/questions/76599075/parse-uml-class-diagram-with-plantuml-java-api 的代码：

String source = "@startuml\n" +
            PUT YOUR CLASS DIAGRAM HERE
            "@enduml";

SourceStringReader r = new SourceStringReader(source);
FileOutputStream file = new FileOutputStream("testGroovy2.png");
ClassDiagram cd = (ClassDiagram) r.getBlocks().get(0).getDiagram();
Collection> classes = 
cd.getEntityFactory().root().getChildren();
classes.stream().forEach(c-> System.out.println(c));

从中知道如何获取ClassDiagram

查看 net.sourceforge.plantuml.xmi.XmiClassDiagramAbstract 中 XmiClassDiagramStandard 的定义：

public class XmiClassDiagramStandard extends XmiClassDiagramAbstract implements XmlDiagramTransformer {
    public XmiClassDiagramStandard(ClassDiagram classDiagram) throws ParserConfigurationException {
        super(classDiagram);
        Iterator var2 = classDiagram.getEntityFactory().leafs().iterator();

        while(var2.hasNext()) {
            Entity ent = (Entity)var2.next();
            Element cla = this.createEntityNode(ent);
            if (cla != null) {
                this.ownedElementRoot.appendChild(cla);
                this.done.add(ent);
            }
        }

    }
}

从中知道如何遍历entity

查看 net.sourceforge.plantuml.xmi.XmiClassDiagramStandard 中的 createEntityNode 方法：

    protected final Element createEntityNode(Entity entity) {
        Element cla = this.document.createElement("UML:Class");
        if (entity.getLeafType() == LeafType.NOTE) {
            return null;
        } else {
            cla.setAttribute("xmi.id", entity.getUid());
            cla.setAttribute("name", entity.getDisplay().get(0).toString());
            Stereotype stereotype = entity.getStereotype();
            if (stereotype != null) {
                Element stereo = this.document.createElement("UML:ModelElement.stereotype");
                Iterator var5 = stereotype.getMultipleLabels().iterator();

                while(var5.hasNext()) {
                    String s = (String)var5.next();
                    Element name = this.document.createElement("UML:Stereotype");
                    name.setAttribute("name", s);
                    stereo.appendChild(name);
                }

                cla.appendChild(stereo);
            }

            LeafType type = entity.getLeafType();
            if (type == LeafType.ABSTRACT_CLASS) {
                cla.setAttribute("isAbstract", "true");
            } else if (type == LeafType.INTERFACE) {
                cla.setAttribute("isInterface", "true");
            }

            if (entity.isStatic()) {
                cla.setAttribute("isStatic", "true");
            }

            if (entity.getVisibilityModifier() == VisibilityModifier.PRIVATE_FIELD || entity.getVisibilityModifier() == VisibilityModifier.PRIVATE_METHOD) {
                cla.setAttribute("visibility", entity.getVisibilityModifier().getXmiVisibility());
            }

            Element feature = this.document.createElement("UML:Classifier.feature");
            cla.appendChild(feature);

            Member m;
            Element operation;
            VisibilityModifier visibility;
            ListIterator var13;
            CharSequence cs;
            for(var13 = entity.getBodier().getFieldsToDisplay().iterator(); var13.hasNext(); feature.appendChild(operation)) {
                cs = (CharSequence)var13.next();
                m = (Member)cs;
                operation = this.document.createElement("UML:Attribute");
                operation.setAttribute("xmi.id", "att" + this.classDiagram.getUniqueSequence());
                operation.setAttribute("name", m.getDisplay(false));
                visibility = m.getVisibilityModifier();
                if (visibility != null) {
                    operation.setAttribute("visibility", visibility.getXmiVisibility());
                }

                if (m.isStatic()) {
                    operation.setAttribute("isStatic", "true");
                }
            }

            for(var13 = entity.getBodier().getMethodsToDisplay().iterator(); var13.hasNext(); feature.appendChild(operation)) {
                cs = (CharSequence)var13.next();
                m = (Member)cs;
                operation = this.document.createElement("UML:Operation");
                operation.setAttribute("xmi.id", "att" + this.classDiagram.getUniqueSequence());
                operation.setAttribute("name", m.getDisplay(false));
                visibility = m.getVisibilityModifier();
                if (visibility != null) {
                    operation.setAttribute("visibility", visibility.getXmiVisibility());
                }

                if (m.isStatic()) {
                    operation.setAttribute("isStatic", "true");
                }
            }

            return cla;
        }
    }

从中可以看出：

• entity.getBodier().getFieldsToDisplay().iterator() 是获取entity的attribute的迭代器
• entity.getBodier().getMethodsToDisplay().iterator() 是获取entity的operation的迭代器
• name ， isAbstract ， isInterface 和 isStatic 这些属性是如何获取的

还有 https://github.com/plantuml/plantuml/pull/1298/files 是2023年2月的一个PR（写本文时尚未Merge），可以作为参考（有待阅读）。

使用JAVA代码将PlantUML类图导出为XMI

通过调用exportDiagram方法

import net.sourceforge.plantuml.FileFormat;  
import net.sourceforge.plantuml.FileFormatOption;  
import net.sourceforge.plantuml.SourceStringReader;

import java.io.FileOutputStream;

public class Main {  
    public static void main(String[] args) throws IOException {
        OutputStream output = new FileOutputStream("test.xmi");
        
        FileFormatOption fileFormatOption = new FileFormatOption(FileFormat.XMI_ARGO);

        String content = new String(Files.readAllBytes(Paths.get("a.puml")));
        SourceStringReader reader = new SourceStringReader(content);

        reader.getBlocks().get(0).getDiagram().exportDiagram(output, 0, fileFormatOption);
    }
}

其中 FileFormat 是一个枚举，定义了 XMI_STANDARD ， XMI_STAR 和 XMI_ARGO 等格式

分析getDiagram的调用链

getDiagram 方法来自 net.sourceforge.plantuml.core.Diagram 提供的 exportDiagram 接口方法，其实现：

    public final ImageData exportDiagram(OutputStream os, int index, FileFormatOption fileFormatOption) throws IOException {
        long now = System.currentTimeMillis();

        ImageData var6;
        try {
            var6 = this.exportDiagramNow(os, index, fileFormatOption);
        } finally {
            if (OptionFlags.getInstance().isEnableStats()) {
                StatsUtilsIncrement.onceMoreGenerate(System.currentTimeMillis() - now, this.getClass(), fileFormatOption.getFileFormat());
            }

        }

        return var6;
    }

其中主要是调用了 net.sourceforge.plantuml.AbstractPSystem 中的 exportDiagramNow 接口方法。而其在 net.sourceforge.plantuml.UmlDiagram 中的实现如下：

    protected final ImageData exportDiagramNow(OutputStream os, int index, FileFormatOption fileFormatOption) throws IOException {
        fileFormatOption = fileFormatOption.withTikzFontDistortion(this.getSkinParam().getTikzFontDistortion());
        if (fileFormatOption.getFileFormat() == FileFormat.PDF) {
            return this.exportDiagramInternalPdf(os, index);
        } else {
            try {
                ImageData imageData = this.exportDiagramInternal(os, index, fileFormatOption);
                this.lastInfo = new XDimension2D((double)imageData.getWidth(), (double)imageData.getHeight());
                return imageData;
            } catch (NoStyleAvailableException var5) {
                this.exportDiagramError(os, var5, fileFormatOption, (String)null);
                return ImageDataSimple.error(var5);
            } catch (UnparsableGraphvizException var6) {
                Logme.error(var6);
                this.exportDiagramError(os, var6.getCause(), fileFormatOption, var6.getGraphvizVersion());
                return ImageDataSimple.error(var6);
            } catch (Throwable var7) {
                this.exportDiagramError(os, var7, fileFormatOption, (String)null);
                return ImageDataSimple.error(var7);
            }
        }
    }

可以看出其主要是调用了 net.sourceforge.plantuml.UmlDiagram.exportDiagramInternal 接口方法，由于当前的类是 ClassDiagram ，其将调用 net.sourceforge.plantuml.classdiagram.ClassDiagram 实现的 exportDiagramInternal 方法：

    protected final ImageData exportDiagramInternal(OutputStream os, int index, FileFormatOption fileFormatOption) throws IOException {
        return this.useLayoutExplicit != 0 ? this.exportLayoutExplicit(os, index, fileFormatOption) : super.exportDiagramInternal(os, index, fileFormatOption);
    }

其中 net.sourceforge.plantuml.classdiagram.ClassDiagram 继承 net.sourceforge.plantuml.objectdiagram.AbstractClassOrObjectDiagram 继承 net.sourceforge.plantuml.classdiagram.AbstractEntityDiagram 继承 net.atmp.CucaDiagram

而 net.atmp.CucaDiagram.exportDiagramInternal 方法中涉及XMI的部分如下：

                this.createFilesXmi(os, fileFormat);
                return ImageDataSimple.ok();

其调用了 net.atmp.CucaDiagram.createFilesXmi 方法，其定义如下：

    private void createFilesXmi(OutputStream suggestedFile, FileFormat fileFormat) throws IOException {
        CucaDiagramXmiMaker maker = new CucaDiagramXmiMaker(this, fileFormat);
        maker.createFiles(suggestedFile);
    }

其中调用了 net.sourceforge.plantuml.xmi.CucaDiagramXmiMaker 的 createFiles 方法，其定义如下：

    public void createFiles(OutputStream fos) throws IOException {
        try {
            Object xmi;
            if (this.diagram instanceof StateDiagram) {
                xmi = new XmiStateDiagram((StateDiagram)this.diagram);
            } else if (this.diagram instanceof DescriptionDiagram) {
                xmi = this.createDescriptionDiagram();
            } else {
                if (!(this.diagram instanceof ClassDiagram)) {
                    throw new UnsupportedOperationException("Diagram type " + this.diagram.getUmlDiagramType() + " is not supported in XMI");
                }

                xmi = this.createClassDiagram();
            }

            ((XmlDiagramTransformer)xmi).transformerXml(fos);
        } catch (ParserConfigurationException var3) {
            Log.error(var3.toString());
            Logme.error(var3);
            throw new IOException(var3.toString());
        } catch (TransformerException var4) {
            Log.error(var4.toString());
            Logme.error(var4);
            throw new IOException(var4.toString());
        }
    }

可以看出涉及创建xmi文件的关键2行为：

xmi = this.createClassDiagram();
((XmlDiagramTransformer)xmi).transformerXml(fos);

而 createClassDiagram 的定义如下：

    private XmlDiagramTransformer createClassDiagram() throws ParserConfigurationException {
        if (this.fileFormat == FileFormat.XMI_STANDARD) {
            return new XmiClassDiagramStandard((ClassDiagram)this.diagram);
        } else if (this.fileFormat == FileFormat.XMI_ARGO) {
            return new XmiClassDiagramArgo((ClassDiagram)this.diagram);
        } else if (this.fileFormat == FileFormat.XMI_SCRIPT) {
            return new XmiClassDiagramScript((ClassDiagram)this.diagram);
        } else if (this.fileFormat == FileFormat.XMI_STAR) {
            return new XmiClassDiagramStar((ClassDiagram)this.diagram);
        } else {
            throw new UnsupportedOperationException();
        }
    }

分析getDiagram方法后，调用内部API导出XMI

import net.sourceforge.plantuml.FileFormat;  
import net.sourceforge.plantuml.FileFormatOption;  
import net.sourceforge.plantuml.SourceStringReader;
import net.sourceforge.plantuml.xmi.XmiClassDiagramArgo;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;

import java.io.FileOutputStream;

public class Main {  
    public static void main(String[] args) throws IOException, ParserConfigurationException, TransformerException {
        OutputStream fos = new FileOutputStream("test2.xmi");
        
        FileFormatOption fileFormatOption = new FileFormatOption(FileFormat.XMI_ARGO);

        String content = new String(Files.readAllBytes(Paths.get("a.puml")));
        SourceStringReader reader = new SourceStringReader(content);
        ClassDiagram classDiagram = (ClassDiagram) reader.getBlocks().get(0).getDiagram();

        Object xmi = new XmiClassDiagramArgo(classDiagram);
        ((XmlDiagramTransformer)xmi).transformerXml(fos);
    }
}

读取一个uml文件并打印其中的属性信息

现在了解了一些后，使用以下Java代码来查看UML文件的信息

package org.example;

import net.sourceforge.plantuml.SourceStringReader;
import net.sourceforge.plantuml.abel.Entity;
import net.sourceforge.plantuml.abel.LeafType;
import net.sourceforge.plantuml.abel.Link;
import net.sourceforge.plantuml.classdiagram.ClassDiagram;
import net.sourceforge.plantuml.cucadiagram.Member;
import net.sourceforge.plantuml.skin.VisibilityModifier;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Iterator;

import java.util.ListIterator;


public class Main {
    public static void main(String[] args) throws IOException, ParserConfigurationException, TransformerException {
        OutputStream output = new FileOutputStream("test.xmi");
//        String source = "@startuml\n";
//        source += "Bob -> Alice : hello\n";
//        source += "@enduml\n";
        String content = new String(Files.readAllBytes(Paths.get("a.puml")));

        SourceStringReader reader = new SourceStringReader(content);
        ClassDiagram classDiagram = (ClassDiagram) reader.getBlocks().get(0).getDiagram();

        String titleName = classDiagram.getTitleDisplay().get(0).toString();
        System.out.println("title: " + titleName);
        Iterator var2 = classDiagram.getEntityFactory().leafs().iterator();

        while(var2.hasNext()) {
            Entity entity = (Entity)var2.next();

            System.out.println("----------------------------------");
            System.out.println("uid: " + entity.getUid());
            if (entity.getLeafType() == LeafType.NOTE) {
//                entity.isAloneAndUnlinked();
//                System.out.println("Entity type: " + entity.getLeafType());
            } else {

                Iterator var1 = classDiagram.getLinks().iterator();
                while(var1.hasNext()) {
                    Link link = (Link)var1.next();
                    if (link.contains(entity)) {
                        Entity other = link.getOther(entity);
                        if (other.getLeafType() == LeafType.NOTE) {
                            System.out.println("Note: "  + other.getDisplay().get(0).toString());
                        }
                    }
                }

                System.out.println("Entity type: " + entity.getLeafType());

                String entityName = entity.getDisplay().get(0).toString();
                System.out.println("Entity name: " + entityName);
                System.out.println("Package: " + entity.getQuark().getParent().toString());

                LeafType type = entity.getLeafType();

                if (type == LeafType.ABSTRACT_CLASS) {
                    System.out.println("isAbstract");
                } else if (type == LeafType.INTERFACE) {
                    System.out.println("isInterface");
                }

                if (entity.isStatic()) {
                    System.out.println(("isStatic"));
                }

                if (entity.getVisibilityModifier() == VisibilityModifier.PRIVATE_FIELD || entity.getVisibilityModifier() == VisibilityModifier.PRIVATE_METHOD) {
                    System.out.println("visibility: " + entity.getVisibilityModifier().getXmiVisibility());
                }

                Member m;
                VisibilityModifier visibility;
                ListIterator var13;
                CharSequence cs;
                for (var13 = entity.getBodier().getFieldsToDisplay().iterator(); var13.hasNext();) {
                    cs = (CharSequence)var13.next();
                    m = (Member) cs;
                    System.out.println("field name: " + m.getDisplay(false));
                    visibility = m.getVisibilityModifier();
                    if (visibility != null) {
                        System.out.println("visibility: " + visibility.getXmiVisibility());
                    }

                    if (m.isStatic()) {
                        System.out.println("isStatic");
                    }
                }

                for (var13 = entity.getBodier().getMethodsToDisplay().iterator(); var13.hasNext();) {
                    cs = (CharSequence)var13.next();
                    m = (Member) cs;
                    System.out.println("operation name: " + m.getDisplay(false));

                    visibility = m.getVisibilityModifier();
                    if (visibility != null) {
                        System.out.println("visibility: " + visibility.getXmiVisibility());
                    }

                    if (m.isStatic()) {
                        System.out.println("isStatic");
                    }
                }
            }

        }

// Write the first image to "png"
//        String desc = reader.outputImage(output).getDescription();
// Return a null string if no generation
    }
}

创建JAVA项目并打包为JAR包：将PlantUML导出为自定义格式的XMI文件

创建项目

使用IDEA创建一个maven项目，然后打开plantuml的maven仓库页面： https://mvnrepository.com/artifact/net.sourceforge.plantuml/plantuml/1.2024.6 将dependency标签拷贝到pom.xml中

添加用于自定义XMI格式的类

由于不能引用 XmiClassDiagramAbstract （提示 is not public in 'net.sourceforge.plantuml.xmi'. Cannot be accessed from outside package），所以在 src/main/java 下新建package net.sourceforge.plantuml.xmi

然后添加类 XmiClassDiagramCustom （extends XmiClassDiagramAbstract）：

package net.sourceforge.plantuml.xmi;

import java.util.Iterator;
import java.util.ListIterator;
import javax.xml.parsers.ParserConfigurationException;

import net.sourceforge.plantuml.abel.Entity;
import net.sourceforge.plantuml.abel.LeafType;
import net.sourceforge.plantuml.abel.Link;
import net.sourceforge.plantuml.classdiagram.ClassDiagram;
import net.sourceforge.plantuml.cucadiagram.Member;
import net.sourceforge.plantuml.decoration.LinkDecor;
import net.sourceforge.plantuml.klimt.creole.Display;
import net.sourceforge.plantuml.skin.VisibilityModifier;
import net.sourceforge.plantuml.stereo.Stereotype;
import org.w3c.dom.Element;

public class XmiClassDiagramCustom extends XmiClassDiagramAbstract implements XmlDiagramTransformer {
    public XmiClassDiagramCustom(ClassDiagram classDiagram) throws ParserConfigurationException {
        super(classDiagram);
        Iterator var2 = classDiagram.getEntityFactory().leafs().iterator();

        Element titleElement = this.document.createElement("UML:Title");
        titleElement.setAttribute("name", classDiagram.getTitleDisplay().get(0).toString());
        this.ownedElementRoot.appendChild(titleElement);

        while(var2.hasNext()) {
            Entity ent = (Entity)var2.next();
            Element cla = this.createEntityNodeCustom(ent, classDiagram);
            if (cla != null) {
                this.ownedElementRoot.appendChild(cla);
                this.done.add(ent);
            }
        }

        var2 = classDiagram.getLinks().iterator();

        while(var2.hasNext()) {
            Link link = (Link)var2.next();
            this.addLink(link);
        }

    }

    protected final Element createEntityNodeCustom(Entity entity, ClassDiagram classDiagram) {
        Element cla = this.document.createElement("UML:Class");
        if (entity.getLeafType() == LeafType.NOTE) {
            return null;
        } else {
            cla.setAttribute("xmi.id", entity.getUid());
            cla.setAttribute("name", entity.getDisplay().get(0).toString());

            // Get Note:
            Iterator var1 = classDiagram.getLinks().iterator();
            while(var1.hasNext()) {
                Link link = (Link)var1.next();
                if (link.contains(entity)) {
                    Entity other = link.getOther(entity);
                    if (other.getLeafType() == LeafType.NOTE) {
                        cla.setAttribute("note", other.getDisplay().get(0).toString());
//                        System.out.println("Note: "  + other.getDisplay().get(0).toString());
                    }
                }
            }

            cla.setAttribute("package", entity.getQuark().getParent().toString());

            Stereotype stereotype = entity.getStereotype();
            if (stereotype != null) {
                Element stereo = this.document.createElement("UML:ModelElement.stereotype");
                Iterator var5 = stereotype.getMultipleLabels().iterator();

                while(var5.hasNext()) {
                    String s = (String)var5.next();
                    Element name = this.document.createElement("UML:Stereotype");
                    name.setAttribute("name", s);
                    stereo.appendChild(name);
                }

                cla.appendChild(stereo);
            }

            LeafType type = entity.getLeafType();
            if (type == LeafType.ABSTRACT_CLASS) {
                cla.setAttribute("isAbstract", "true");
            } else if (type == LeafType.INTERFACE) {
                cla.setAttribute("isInterface", "true");
            }

            if (entity.isStatic()) {
                cla.setAttribute("isStatic", "true");
            }

            if (entity.getVisibilityModifier() == VisibilityModifier.PRIVATE_FIELD || entity.getVisibilityModifier() == VisibilityModifier.PRIVATE_METHOD) {
                cla.setAttribute("visibility", entity.getVisibilityModifier().getXmiVisibility());
            }

            Element feature = this.document.createElement("UML:Classifier.feature");
            cla.appendChild(feature);

            Member m;
            Element operation;
            VisibilityModifier visibility;
            ListIterator var13;
            CharSequence cs;
            for(var13 = entity.getBodier().getFieldsToDisplay().iterator(); var13.hasNext(); feature.appendChild(operation)) {
                cs = (CharSequence)var13.next();
                m = (Member)cs;
                operation = this.document.createElement("UML:Attribute");
                operation.setAttribute("xmi.id", "att" + this.classDiagram.getUniqueSequence());
                operation.setAttribute("name", m.getDisplay(false));
                visibility = m.getVisibilityModifier();
                if (visibility != null) {
                    operation.setAttribute("visibility", visibility.getXmiVisibility());
                }

                if (m.isStatic()) {
                    operation.setAttribute("isStatic", "true");
                }
            }

            for(var13 = entity.getBodier().getMethodsToDisplay().iterator(); var13.hasNext(); feature.appendChild(operation)) {
                cs = (CharSequence)var13.next();
                m = (Member)cs;
                operation = this.document.createElement("UML:Operation");
                operation.setAttribute("xmi.id", "att" + this.classDiagram.getUniqueSequence());
                operation.setAttribute("name", m.getDisplay(false));
                visibility = m.getVisibilityModifier();
                if (visibility != null) {
                    operation.setAttribute("visibility", visibility.getXmiVisibility());
                }

                if (m.isStatic()) {
                    operation.setAttribute("isStatic", "true");
                }
            }

            return cla;
        }
    }

    // copy from XmiClassDiagramStar
    private void addLink(Link link) {
        if (!link.isHidden() && !link.isInvis()) {
            String assId = "ass" + this.classDiagram.getUniqueSequence();
            if (link.getType().getDecor1() != LinkDecor.EXTENDS && link.getType().getDecor2() != LinkDecor.EXTENDS) {
                Element association = this.document.createElement("UML:Association");
                association.setAttribute("xmi.id", assId);
                association.setAttribute("namespace", CucaDiagramXmiMaker.getModel(this.classDiagram));
                if (!Display.isNull(link.getLabel())) {
                    association.setAttribute("name", this.forXMI(link.getLabel()));
                }

                Element connection = this.document.createElement("UML:Association.connection");
                Element end1 = this.document.createElement("UML:AssociationEnd");
                end1.setAttribute("xmi.id", "end" + this.classDiagram.getUniqueSequence());
                end1.setAttribute("association", assId);
                end1.setAttribute("type", link.getEntity1().getUid());
                if (link.getQuantifier1() != null) {
                    end1.setAttribute("name", this.forXMI(link.getQuantifier1()));
                }

                Element endparticipant1 = this.document.createElement("UML:AssociationEnd.participant");
                if (link.getType().getDecor2() == LinkDecor.COMPOSITION) {
                    end1.setAttribute("aggregation", "composite");
                }

                if (link.getType().getDecor2() == LinkDecor.AGREGATION) {
                    end1.setAttribute("aggregation", "aggregate");
                }

                end1.appendChild(endparticipant1);
                connection.appendChild(end1);
                Element end2 = this.document.createElement("UML:AssociationEnd");
                end2.setAttribute("xmi.id", "end" + this.classDiagram.getUniqueSequence());
                end2.setAttribute("association", assId);
                end2.setAttribute("type", link.getEntity2().getUid());
                if (link.getQuantifier2() != null) {
                    end2.setAttribute("name", this.forXMI(link.getQuantifier2()));
                }

                Element endparticipant2 = this.document.createElement("UML:AssociationEnd.participant");
                if (link.getType().getDecor1() == LinkDecor.COMPOSITION) {
                    end2.setAttribute("aggregation", "composite");
                }

                if (link.getType().getDecor1() == LinkDecor.AGREGATION) {
                    end2.setAttribute("aggregation", "aggregate");
                }

                end2.appendChild(endparticipant2);
                connection.appendChild(end2);
                association.appendChild(connection);
                this.ownedElementRoot.appendChild(association);
            } else {
                this.addExtension(link, assId);
            }
        }
    }

    // copy from XmiClassDiagramStar
    private void addExtension(Link link, String assId) {
        Element association = this.document.createElement("UML:Generalization");
        association.setAttribute("xmi.id", assId);
        association.setAttribute("namespace", CucaDiagramXmiMaker.getModel(this.classDiagram));
        if (link.getLabel() != null) {
            association.setAttribute("name", this.forXMI(link.getLabel()));
        }

        if (link.getType().getDecor1() == LinkDecor.EXTENDS) {
            association.setAttribute("child", link.getEntity1().getUid());
            association.setAttribute("parent", link.getEntity2().getUid());
        } else {
            if (link.getType().getDecor2() != LinkDecor.EXTENDS) {
                throw new IllegalStateException();
            }

            association.setAttribute("child", link.getEntity2().getUid());
            association.setAttribute("parent", link.getEntity1().getUid());
        }

        this.ownedElementRoot.appendChild(association);
    }
}

添加导出类（入口）

添加package org.export ，并添加类 UML2XMIExporter ：

package org.export;

import net.sourceforge.plantuml.SourceStringReader;
import net.sourceforge.plantuml.classdiagram.ClassDiagram;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;


import net.sourceforge.plantuml.xmi.XmiClassDiagramCustom;
import net.sourceforge.plantuml.xmi.XmlDiagramTransformer;

public class UML2XMIExporter {
    public static void main(String[] args) throws IOException, ParserConfigurationException, TransformerException {

        String content = new String(Files.readAllBytes(Paths.get(args[0])));
        OutputStream outputCustom = Files.newOutputStream(Paths.get(args[1]));

        SourceStringReader reader = new SourceStringReader(content);
        ClassDiagram classDiagram = (ClassDiagram) reader.getBlocks().get(0).getDiagram();

        // 导出XMI
        XmlDiagramTransformer xmi = new XmiClassDiagramCustom(classDiagram);
        xmi.transformerXml(outputCustom);

    }
}

打包

接下来，参考 https://blog.csdn.net/weixin_41229430/article/details/138963215 打包为jar包

创建文件： src/main/assembly/assembly.xml， 内容如下：

    assembly
    
        zip
        jar
        tar.gz
    
    false
    
        
        
            src/main/resources
            conf
            
                *.xml
                *.properties
                **/*.xml
                **/*.properties
            
            0644
        
        
            assembly/bin
            bin
            0755
        
    
    
        
            lib
        
    

然后在pom.xml中添加

    
        
            
            
                org.apache.maven.plugins
                maven-assembly-plugin
                3.3.0
                
                    
                        make-assembly2
                        package
                        
                            single
                        
                        
                            
                                ${basedir}/src/main/assembly/assembly.xml
                            
                            
                                
                                    org.export.UML2XMIExporter
                                    true
                                    lib/
                                    false
                                
                            
                            
                                jar-with-dependencies
                            
                        
                    
                
            

            
                org.apache.maven.plugins
                maven-compiler-plugin
                3.8.1
                
                    1.8
                    1.8
                
            
        
    

点击IDEA右侧的m图标（maven），双击Lifecycle下的package。然后在target目录下可以看到已经生成了jar包。

打开command prompt命令行（不要使用powershell）运行：

java -Dfile.encoding=UTF-8 -jar custom-plantuml-xmi-export-1.0-SNAPSHOT-jar-with-dependencies.jar input.puml output.xmi