jaxb unmarshalling by declaring types does not work when there is no namespace-Java-php.cn

jaxb unmarshalling by declaring types does not work when there is no namespace

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Release： 2024-02-06 09:09:09

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I am building a parser for vast documents, which are xml documents, there is an official xsd, there are several versions: https://github.com/interactiveadvertisingbureau/ vast/tree/master

I needed to be able to unmarshal the incoming xml, so I generated the model using jaxb2-maven-plugin.

I need to be able to handle incoming xml, which may or may not mention namespaces: my problem is that it works when there is a namespace, but not when there is no namespace.

As per https://stackoverflow.com/a/8717287/3067542 and https://docs.oracle.com/javase/6/docs/api/javax/xml/bind/unmarshaller.html#unmarshalbydeclaredtype, I understand There is a workaround because I know the target class type so I can force unmarshalling to that class regardless of namespace or not.

This is my code (also available on github)

JAXBContext jc = JAXBContext.newInstance(VAST.class);
Unmarshaller u = jc.createUnmarshaller();

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);

DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new InputSource(new StringReader(xmlString)));
JAXBElement<VAST> foo = u.unmarshal( doc, VAST.class);

return new CustomVast(foo.getValue());

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When running the test, I found that the inner class was not populated:

Did I miss something? Is there an additional flag that needs to be set when generating classes using jaxb2-maven-plugin so that it can work?

Correct answer

This answer is obviously not optimized, but will give you a hint on how to make it work on version 4.2 of namespace and non-namespace xml:

Here is the body method of parsexml

jaxbcontext jc = jaxbcontext.newinstance(vast.class);
unmarshaller u = jc.createunmarshaller();

// should be optimized
transformerfactory tf = transformerfactory.newinstance();
stringwriter sw = new stringwriter();
url urlxslt = vastparser.class.getclassloader().getresource("xslt/vast_4.2.xslt");
file filexslt = new file(urlxslt.touri());
transformer t = tf.newtransformer(new streamsource(new fileinputstream(filexslt)));
// transform original xml with xslt to always add the namespace in the parsing 
t.transform(new streamsource(new stringreader(xmlstring)), new streamresult(sw));

// unmarshall transformed xml
jaxbelement<vast> foo = u.unmarshal(new streamsource(new stringreader(sw.tostring())), vast.class);

return new customvast(foo.getvalue());

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src/main/resources/xslt/vast_4.2.xslt is:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="@*|text()|comment()|processing-instruction()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>

    <!-- adds the xmlns part to the VAST element -->
    <xsl:template match="/VAST">
        <VAST xmlns="http://www.iab.com/VAST">
            <xsl:apply-templates select="@*|node()"/>
        </VAST>
    </xsl:template>

    <xsl:template match="*">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

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At this point, both unit tests apply to Section 4.2.

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