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java, xsd & marshalling: jre bug, my fault or xsd issues?
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javaxmljaxbxsd
O

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I am running into a problem while marshalling a JAXB model tree to a xml file.

I created those model classes using xjc. I cannot modify these xml schemas - they are defined externally (similar to this question which lacks for answers).

The xml schema files seems to be valid according xjc (and other xml tools). I am asking whether

  • this is a java/jre bug or
  • I am doing something wrong or
  • if the schema files are somewhat errornous

and how to resolve this issue.

The exception which I get is:

com.sun.istack.internal.SAXException2: "com.mypackage.A" is substituting "com.mypackage.BaseType", but "com.mypackage.A" is bound to an anonymous type.
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:237)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:652)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementNodeProperty.serializeItem(ArrayElementNodeProperty.java:54)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody(ArrayElementProperty.java:157)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:335)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:335)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:146)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:116)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeBody(ElementBeanInfoImpl.java:318)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:325)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:61)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayReferenceNodeProperty.serializeListBody(ArrayReferenceNodeProperty.java:103)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementNodeProperty.serializeItem(ArrayElementNodeProperty.java:54)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody(ArrayElementProperty.java:157)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:141)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:116)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeBody(ElementBeanInfoImpl.java:318)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:325)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:61)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:483)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:95)

(java 7 update 45)

Outstretched answered 27/1, 2014 at 17:11 Comment(5)
It would be more helpful if you could post a small sample which actually produces that outcome - it is hard to diagnose the reason only on the stack-trace. Have you already tried different JVM versions - even within the same master-version? – Authors
@RomanVottner You're right, but unfortunately, I'm not allowed to publish these XSDs and the corresponding code. But maybe I can try to make a minimalistic example which does not use the actual files. – Outstretched
Unless you provide a sample nobody can help you. – Flypaper
Does your schema use inheritance or declare a complexType within an element? JAXB can have problems with both, but you might be able to work around it using binding customizations. JAXB seems to be playing dumb about substitution groups. – Cannot
@LeosLiterak - I was able to recreate example code based on his exception: https://mcmap.net/q/1079516/-java-xsd-amp-marshalling-jre-bug-my-fault-or-xsd-issues – Titanite
T
13

TL;DR

java, xsd & marshalling: jre bug, my fault or xsd issues?

It's your fault :). Continue reading for the reason why.

Java Model

Below is a Java model that is based on the one hinted at in your question that can be used to produce the same exception that you are seeing.

Root

Below is a root object that has one property. The type of that property has two subclasses. One of the subclasses (B) corresponds to a named type, and the other (A) to an anonymous type. 

package com.mypackage;

import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Root {

    private BaseType baseType;

    public BaseType getBaseType() {
        return baseType;
    }

    public void setBaseType(BaseType baseType) {
        this.baseType = baseType;
    }

}

BaseType

This is the super class. It has two subclasses: A and B.

package com.mypackage;

import javax.xml.bind.annotation.XmlSeeAlso;

@XmlSeeAlso({A.class, B.class})
public class BaseType {

}

A

The A class corresponds to an anonymous complex type. An anonymous type is represented with the @XmlType(name="") annotation.

package com.mypackage;

import javax.xml.bind.annotation.XmlType;

@XmlType(name="")
public class A extends BaseType {

}

B

The B class corresponds to the named complex type b. The default is the same as having @XmlType(name="b").

package com.mypackage;

public class B extends BaseType {

}

Demo Code - That Reproduces Error

Demo

When the baseType property on the Root class is one of the subclasses then the xsi:type attribute is added to qualify the element (similar to a cast in Java). The instance is required to correspond to a named complex type. In this case A does not.

package com.mypackage;

import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Root root = new Root();
        BaseType baseType = new A(); // Invalid Value
        root.setBaseType(baseType);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }

}

Exception

This results in the following exception. As stated by the exception A is not a valid substitute for BaseType because it corresponds to an anonymous complex type, since since it corresponds to an anonymous type it doesn't have the necessary value for the xsi:type attribute.

Exception in thread "main" javax.xml.bind.MarshalException
 - with linked exception:
[com.sun.istack.internal.SAXException2: Instance of "com.mypackage.A" is substituting "com.mypackage.BaseType", but "com.mypackage.A" is bound to an anonymous type.]
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:311)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:95)
    at com.mypackage.Demo.main(Demo.java:16)
Caused by: com.sun.istack.internal.SAXException2: Instance of "com.mypackage.A" is substituting "com.mypackage.BaseType", but "com.mypackage.A" is bound to an anonymous type.
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:237)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:652)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:582)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:325)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:483)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308)
    ... 3 more

Demo Code - That Works

Demo

If instead of A you specified the other subclass B which corresponds to a named complex type.

package com.mypackage;

import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Root root = new Root();
        BaseType baseType = new B(); // Valid Value
        root.setBaseType(baseType);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }

}

Output

Then you will see everything works as expected an the type name is included when the baseType property is marshalled.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <baseType xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="b"/>
</root>
Titanite answered 15/4, 2014 at 19:48 Comment(0)

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