CODEWITHSUNDEEP
javaxmldtddoctype
Stephan
Stephan

Reputation:

How can I ignore DTD validation but keep the Doctype when writing an XML file?

I am working on a system that should be able to read any (or at least, any well-formed) XML file, manipulate a few nodes and write them back into that same file. I want my code to be as generic as possible and I don't want

The aim is to have the source file entirely unchanged except for the changed Nodes, which are retrieved via XPath. I would like to get away with the standard javax.xml stuff.

My progress so far:

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

    factory.setAttribute("http://xml.org/sax/features/namespaces", true);
    factory.setAttribute("http://xml.org/sax/features/validation", false);
    factory.setAttribute("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
    factory.setAttribute("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

    factory.setNamespaceAware(true);
    factory.setIgnoringElementContentWhitespace(false);
    factory.setIgnoringComments(false);
    factory.setValidating(false);
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document document = builder.parse(new InputSource(inStream));

This loads the XML source into a org.w3c.dom.Document successfully, ignoring DTD validation. I can do my replacements and then I use 

    Source source = new DOMSource(document);
    Result result = new StreamResult(getOutputStream(getPath()));

    // Write the DOM document to the file
    Transformer xformer = TransformerFactory.newInstance().newTransformer();
    xformer.transform(source, result);

to write it back. Which is nearly perfect. But the Doctype tag is gone, no matter what I do. While debugging, I saw that there is a DeferredDoctypeImpl [log4j:configuration: null] object in the Document object after parsing, but it is somehow wrong, empty or ignored. The file I tested on starts like this (but it is the same for other file types):

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false">

[...]

I think there are a lot of (easy?) ways involving hacks or pulling additional JARs into the project. But I would rather like to have it with the tools I already use.

Upvotes: 2

Views: 12138

Answers (3)

Zee
Zee

Reputation: 1420

I tried using the LSSerializer library and was unable to get anywhere with it in terms of retaining the Doctype. This is the solution that Stephan probably used Note: This is in scala but uses a java library so just convert your code

import com.sun.org.apache.xml.internal.serialize.{OutputFormat, XMLSerializer}
 def transformXML(root: Element, file: String): Unit = {
    val doc = root.getOwnerDocument
    val format = new OutputFormat(doc)
    format.setIndenting(true)
    val writer = new OutputStreamWriter(new FileOutputStream(new File(file)))
    val serializer = new XMLSerializer(writer, format)
    serializer.serialize(doc)

  }

Upvotes: 0

Mihai Chintoanu
Mihai Chintoanu

Reputation: 3265

Here's how you could do it using the LSSerializer found in JDK:

    private void writeDocument(Document doc, String filename)
            throws IOException {
        Writer writer = null;
        try {
            /*
             * Could extract "ls" to an instance attribute, so it can be reused.
             */
            DOMImplementationLS ls = (DOMImplementationLS) 
                    DOMImplementationRegistry.newInstance().
                            getDOMImplementation("LS");
            writer = new OutputStreamWriter(new FileOutputStream(filename));
            LSOutput lsout = ls.createLSOutput();
            lsout.setCharacterStream(writer);
            /*
             * If "doc" has been constructed by parsing an XML document, we
             * should keep its encoding when serializing it; if it has been
             * constructed in memory, its encoding has to be decided by the
             * client code.
             */
            lsout.setEncoding(doc.getXmlEncoding());
            LSSerializer serializer = ls.createLSSerializer();
            serializer.write(doc, lsout);
        } catch (Exception e) {
            throw new IOException(e);
        } finally {
            if (writer != null) writer.close();
        }
    }

Needed imports:

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import org.w3c.dom.Document;
import org.w3c.dom.bootstrap.DOMImplementationRegistry;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSOutput;
import org.w3c.dom.ls.LSSerializer;

I know this is an old question which has already been answered, but I think the technical details might help someone.

Upvotes: 0

Stephan
Stephan

Reputation:

Sorry, got it right now using a XMLSerializer instead of the Transformer...

Upvotes: 1

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