JAXB binding to remove propOrder

Question

I have written an XSD:

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
            targetNamespace="http://api.synthesys/models/generated/simple/chat"
            xmlns:drsc="http://api.synthesys/models/generated/simple/chat"
            xmlns:simplify="http://jaxb2-commons.dev.java.net/basic/simplify"
            jaxb:extensionBindingPrefixes="simplify"
            jaxb:version="2.1">
    <xsd:element name="conversation">
        <xsd:complexType>
            <xsd:sequence>

                <xsd:element name="start-time" type="xsd:dateTime" minOccurs="1" maxOccurs="1"/>


                <xsd:choice minOccurs="0" maxOccurs="unbounded">

                    <!-- for code generation, allowing direct and distinct access to the messages and events -->
                    <xsd:annotation>
                        <xsd:appinfo>
                            <simplify:as-element-property/>
                        </xsd:appinfo>
                    </xsd:annotation>

                    <!--messages-->
                    <xsd:element name="message">
                        <xsd:complexType>
                            <xsd:sequence>
                                <xsd:element name="author" minOccurs="1" maxOccurs="1" type="xsd:string"/>
                                <xsd:element name="text" minOccurs="1" maxOccurs="1" type="xsd:string"/>
                            </xsd:sequence>
                        </xsd:complexType>
                    </xsd:element>

                    <!--room events: entering or exiting the room-->
                    <xsd:element name="event">
                        <xsd:complexType>
                            <xsd:sequence>
                                <xsd:element name="who" minOccurs="1" maxOccurs="1" type="xsd:string"/>
                                <xsd:element name="what" minOccurs="1" maxOccurs="1" type="xsd:string"/>
                            </xsd:sequence>
                        </xsd:complexType>
                    </xsd:element>
                </xsd:choice>

                <!--end time millis-->
                <xsd:element name="end-time" type="xsd:dateTime" minOccurs="1" maxOccurs="1"/>

            </xsd:sequence>

        </xsd:complexType>
    </xsd:element>
</xsd:schema>

and I have written a sample XML file:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<mine:conversation xmlns:mine="http://api.synthesys/models/generated/simple/chat">
    <start-time>2017-09-10T12:00:00.000Z</start-time>
    <event>
        <who>John</who>
        <what>entered the room</what>
    </event>
    <message>
        <author>John</author>
        <text>hello</text>
    </message>
    <event>
        <who>Jane</who>
        <what>entered the room</what>
    </event>
    <message>
        <author>Jane</author>
        <text>goodbye, John</text>
    </message>
    <event>
        <who>Jane</who>
        <what>left the room</what>
    </event>
    <event>
        <who>John</who>
        <what>left the room</what>
    </event>
    <end-time>2017-09-10T12:01:00.000Z</end-time>
</mine:conversation>

And with the maven-jaxb2-plugin I have been able to generate a class from this schema like this:

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "startTime",
    "messages",
    "events",
    "endTime"
})
@XmlRootElement(name = "conversation")
public class Conversation {

    @XmlElement(name = "start-time", required = true, type = String.class)
    @XmlJavaTypeAdapter(Adapter1 .class)
    @XmlSchemaType(name = "dateTime")
    protected XMLGregorianCalendar startTime;
    @XmlElement(name = "message")
    protected List<Conversation.Message> messages;
    @XmlElement(name = "event")
    protected List<Conversation.Event> events;
    @XmlElement(name = "end-time", required = true, type = String.class)
    @XmlJavaTypeAdapter(Adapter1 .class)
    @XmlSchemaType(name = "dateTime")
    protected XMLGregorianCalendar endTime; 

The problem is that when I try to use JAXB to unmarshall my sample xml file like this:

class MarshalUnmarshalTest extends Specification {
    def "test"(){
        setup:
        SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
        JAXBContext context = JAXBContext.newInstance(synthesys.api.models.generated.simple.chat.Conversation.class)
        Marshaller marshaller = context.createMarshaller()
        Unmarshaller unmarshaller = context.createUnmarshaller()
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        context.generateSchema(new StructuredDataUtils.StructuredDataSchemaOutputResolver(bos));
        Schema schema = sf.newSchema(new StreamSource(new ByteArrayInputStream(bos.toByteArray())));
        marshaller.setSchema(schema)
        unmarshaller.setSchema(schema)

        File input = new File("src/test/resources/data/genericChat/simple-valid.xml")


        when:
        def object = unmarshaller.unmarshal(input.newInputStream())

        then:
        object instanceof synthesys.api.models.generated.simple.chat.Conversation
    }
}

I get this error:

    javax.xml.bind.UnmarshalException
 - with linked exception:
[org.xml.sax.SAXParseException; lineNumber: 8; columnNumber: 14; cvc-complex-type.2.4.a: Invalid content was found starting with element 'message'. One of '{event, end-time}' is expected.]
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.createUnmarshalException(AbstractUnmarshallerImpl.java:335)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.createUnmarshalException(UnmarshallerImpl.java:563)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:249)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:214)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:204)
    at synthesys.api.models.generated.standard.chat.MarshalUnmarshalTest.test(MarshalUnmarshalTest.groovy:31)
Caused by: org.xml.sax.SAXParseException; lineNumber: 8; columnNumber: 14; cvc-complex-type.2.4.a: Invalid content was found starting with element 'message'. One of '{event, end-time}' is expected.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(ErrorHandlerWrapper.java:134)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:437)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:368)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:325)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator$XSIErrorReporter.reportError(XMLSchemaValidator.java:458)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.reportSchemaError(XMLSchemaValidator.java:3237)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.handleStartElement(XMLSchemaValidator.java:1796)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.startElement(XMLSchemaValidator.java:746)
    at com.sun.org.apache.xerces.internal.jaxp.validation.ValidatorHandlerImpl.startElement(ValidatorHandlerImpl.java:570)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.ValidatingUnmarshaller.startElement(ValidatingUnmarshaller.java:86)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:163)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:509)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:379)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2786)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:117)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:649)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:243)
    ... 4 more

What's really frustrating to me is that this sample file validates when using xmllint --noout --schema path/to/schema.xsd path/to/sample.xml. It seems to me that the main issue is that the generated Conversation class defines a propOrder that is more restrictive than the schema actually is.

Can anyone point me to how I can configure the simplify plugin to not generate this propOrder? Or how I can otherwise leverage bindings to remove that restriction? I do want to maintain the current behavior where my generated class has both a List<Message> messages property and a List<Event> events property, rather than a single List<Object> messagesOrEvents

Answer 1

Disclaimer: I am the author of the JAXB2 Simplify Plugin and JAXB2 Annotate Plugin.

The problem is that simplifying the property (like you did) effectively changes the structure of the XML. It's no longer message, event, end-time in any order. It's some fixed order after the simplification. That's the price you pay for the easier-to-use structure in the Java model.

Can anyone point me to how I can configure the simplify plugin to not generate this propOrder?

No. The simplify plugin does not generate propOrder, XJC does. The simplify plugin only "converts" a heterogeneous property into several simple homogeneous properties. It has nothing to do with propOrder.

It is possible to customize the generated @XmlType annotation using the JAXB2 Annotate Plugin, but I'm not quite sure if propOrder is the problem. To be honest I am somehow surprized that you have problems with the order of elements. I always thought JAXB did not care about the order when unmarshalling.

If you want, please post your minimal sample project under https://github.com/highsource/maven-jaxb2-plugin-support/tree/master/s/simplify, I will take a look.