如何使用 java 读取/写入压缩的 mxGraph 图

Question

我必须阅读和修改一些使用 draw.io（现在 diagrams.net）创建的图表。它们看起来像：

<mxfile pages="1" version="11.1.5"><diagram id="aC-2Vsr7-bsXYD2UCZoz" name="Page-1">zZRNT4QwEEB/DXdo1/24uup60MRkDx5Nl45QLQwpXQF/vWXbAs2KejJ7Ie2bKZ15bRrRbdHuFKvyR+QgIxLzNqI3ESGb5cp8e9BZsNisLciU4BYlI9iLT3AwdvQoONRBokaUWlQhTLEsIdUBY0phE6a9ogx3rVgGZ2CfMnlOnwXXuaVrshr5PYgs9zsny42NFMwnu07qnHFsJojeRnSrELUdFe0WZO/Oe7Hr7maiQ2EKSv3NAjy89T5ILNnBHMkp4UlhCnWNhrrlp+CL0HPxypIHUb6781vFxIZ8IWToZaix1p33p/BYcuhTk4heN7nQsK9Y2kcbc2EMy3UhXfi8JVfGBygN7QS5/XaABWjVmRQX9ba7cNqMZ5d4lk/ObekYc9clG348GjUD16GfOsd/8U1+8U3mfdPQN71k30l8EcLpT7bpjOqrxN96r3px0arX/6baTMd36pQ6eezp7Rc=</diagram></mxfile>

很明显，它们是用 deflate() javascript 函数编码和压缩的。如何使用 Java 解压缩它们？我在 mxUtils 中找不到任何有用的方法来读取压缩图，并且 mxXmlUtils.parseXml(xmlDiagram) 似乎只能解析普通的 text/xml.

通过mxGraph修改后API，如何重新编码压缩图表？

有人知道如何做到这一点吗？

提前致谢！

----根据Thomas的回答修改---

Thomas，您的代码完美无缺！但我还需要 'invert' 它来编码和压缩图表。我试图以相反的顺序进行相同的操作，但似乎放气操作或 Base64 编码以某种方式破坏了图表。以下是我的代码：

//url encoding...
String xmlGraphEncoded = URLEncoder.encode(xmlGraphString, "UTF-8");
xmlGraphEncoded=xmlGraphEncoded.replace("+", "%20");

byte[] bytesToCompress=xmlGraphEncoded.getBytes("UTF-8");
//deflating...

//Deflater deflater = new Deflater(); << do not use this
Deflater deflater = new Deflater(9,true);

deflater.setInput(bytesToCompress);
deflater.finish();
int compressedSize=deflater.deflate(bytesToCompress);
//encoding B64...
compressedEncodedBytes= Base64.encodeBase64(bytesToCompress);

我知道第一个编码效果很好，但在 deflate&Base64 之后，draw-io 转换工具抱怨这个错误：“inflateRaw 失败：无效的存储块长度”

你能帮帮我吗？

Answer 1

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.net.URLDecoder;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;

import org.apache.commons.codec.binary.Base64;


public mxGraphModel diagramStringToGraphModel(String diagramString) throws IOException
{
    if (Base64.isBase64(diagramString))
    {
        byte[] bytes = Base64.decodeBase64(diagramString);
        byte[] buffer = new byte[1024];

        Inflater inflater = new Inflater(true);
        inflater.setInput(bytes);

        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        try (InflaterInputStream iis = new InflaterInputStream(new ByteArrayInputStream(bytes), inflater))
        {
            int bytesRead = 0;
            while ((bytesRead = iis.read(buffer)) != -1)
            {
                bos.write(buffer, 0, bytesRead);
            }
        }

        diagramString = new String(bos.toByteArray());
    }

    String str = URLDecoder.decode(diagramString, "UTF-8");

    Document doc = xmlUtils.parseXml(str);
    mxCodec codec = new mxCodec(doc);

    return (mxGraphModel) codec.decode(doc.getDocumentElement());
}

XMLUtils.java

import java.io.StringReader;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.xml.sax.InputSource;

public synchronized DocumentBuilder getDocumentBuilder()
{
    if (documentBuilder == null)
    {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setExpandEntityReferences(false);
        dbf.setXIncludeAware(false);
        dbf.setValidating(false);

        try
        {
            dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
            dbf.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
            dbf.setFeature("http://xml.org/sax/features/external-general-entities", false);
        }
        catch (ParserConfigurationException e)
        {
            log.log(Level.SEVERE, "Failed to set feature", e);
        }

        try
        {
            documentBuilder = dbf.newDocumentBuilder();
        }
        catch (Exception e)
        {
            log.log(Level.SEVERE, "Failed to construct a document builder", e);
        }
    }
    
    return documentBuilder;
}

public synchronized Document parseXml(String xml)
{
    try
    {
        return getDocumentBuilder().parse(new InputSource(new StringReader(xml)));
    }
    catch (Exception e)
    {
        log.log(Level.SEVERE, "Failed to parse XML", e);
    }
    
    return null;
}

如何使用 java 读取/写入压缩的 mxGraph 图

How to read / write compressed mxGraph diagram with java

mxgraph