I have to add some XMP data to a PDF/A-3 file.

This is the XMP data I want to add:

<pdfaExtension:schemas>
    <rdf:Bag>
       <rdf:li rdf:parseType="Resource">
          <pdfaSchema:schema>Factur-X PDFA Extension Schema</pdfaSchema:schema>
          <pdfaSchema:namespaceURI>urn:factur-x:pdfa:CrossIndustryDocument:invoice:1p0#</pdfaSchema:namespaceURI>
          <pdfaSchema:prefix>fx</pdfaSchema:prefix>
          <pdfaSchema:property>
             <rdf:Seq>
                <rdf:li rdf:parseType="Resource">
                   <pdfaProperty:name>DocumentFileName</pdfaProperty:name>
                   <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                   <pdfaProperty:category>external</pdfaProperty:category>
                   <pdfaProperty:description>name of the embedded XML invoice file</pdfaProperty:description>
                </rdf:li>
                <rdf:li rdf:parseType="Resource">
                   <pdfaProperty:name>DocumentType</pdfaProperty:name>
                   <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                   <pdfaProperty:category>external</pdfaProperty:category>
                   <pdfaProperty:description>INVOICE</pdfaProperty:description>
                </rdf:li>
                <rdf:li rdf:parseType="Resource">
                   <pdfaProperty:name>Version</pdfaProperty:name>
                   <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                   <pdfaProperty:category>external</pdfaProperty:category>
                   <pdfaProperty:description>The actual version of the ZUGFeRD XML schema</pdfaProperty:description>
                </rdf:li>
                <rdf:li rdf:parseType="Resource">
                   <pdfaProperty:name>ConformanceLevel</pdfaProperty:name>
                   <pdfaProperty:valueType>Text</pdfaProperty:valueType>
                   <pdfaProperty:category>external</pdfaProperty:category>
                   <pdfaProperty:description>The selected ZUGFeRD profile completeness</pdfaProperty:description>
                </rdf:li>
             </rdf:Seq>
          </pdfaSchema:property>
       </rdf:li>
    </rdf:Bag>
</pdfaExtension:schemas>

It is an array that contains a structure that in turn contains another array of structures

I tried the following:

1. create the XMP Meta data

XMPMeta xmpMeta = XMPMetaFactory.create();

2. add an array

xmpMeta.appendArrayItem(XMPConst.NS_PDFA_EXTENSION, "schemas", new PropertyOptions(PropertyOptions.ARRAY), "schema", null);

3. add the metadata to my PDF document

pdfDocument.setXmpMetadata(xmpMeta);

By doing this i get the following result:

<pdfaExtension:schemas>
    <rdf:Bag>
        <rdf:li>schema</rdf:li>
    </rdf:Bag>
</pdfaExtension:schemas>

How can i add the scructure node to this array?

I tried to compose the array item path and add the structure to it:

String path = XMPPathFactory.composeArrayItemPath("schemas", 1);

xmpMeta.setStructField(XMPConst.NS_PDFA_EXTENSION, path, XMPConst.NS_PDFA_SCHEMA, "namespaceURI", "Factur-X PDFA Extension Schema", new PropertyOptions(PropertyOptions.STRUCT));

but i get the XMPException “Structs and arrays can’t have values”

Unfortunately I could not find much information about iText and XMP.