Question

My model object look something like this:

@XmlRootElement(name = "appConfig")
@XmlType(propOrder = {})
public class Config implements Serializable {
...
private int advancedFooBar;
...
@XmlElement(name = "advancedfoobar")
public int getAdvancedFooBar() {
    return advancedFooBar;
}

public void setAdvancedFooBar(int advancedFooBar) {
    this.advancedFooBar = advancedFooBar ;
}

When I generate a schema against this class w/JXC I end up with the following for the above property:

<xs:element name="advancedfoobar" type="xs:int"/>

I’d like this to be an optional element so I tried changing

@XmlElement(name = "advancedfoobar")

to

@XmlElement(name = "advancedfoobar", required=false)

However, that did not result any change to the generated schema. What do I need to do so that the “advancedfoobar” element will be defined as optional in the generated schema?

I am using JDK 1.7.0_U3 on Windows 7 Ultimate x64.

Thanks.

-Noah

Answer 1

WHAT THE JAVADOCS SAY

According to the Javadoc for @XmlElement (see: http://docs.oracle.com/javase/6/docs/api/javax/xml/bind/annotation/XmlElement.html#required%28%29)

If required() is false, then the Javabean property is mapped to XML
Schema element declaration with minOccurs=”0″. maxOccurs is “1” for a
single valued property and “unbounded” for a multivalued property.

The schema definition for advancedfoobar should be minOccurs=0 for the following mappings:

@XmlElement(name = "advancedfoobar")
public int getAdvancedFooBar() {
    return advancedFooBar;
}

and

@XmlElement(name = "advancedfoobar", required=false)
public int getAdvancedFooBar() {
    return advancedFooBar;
}

---

BUG IN MOXy AND REFERENCE IMPLEMENTATION

There appears to be a bug in both EclipseLink JAXB (MOXy) and the JAXB reference implementation regarding primitives and optional elements. I have opened the following bug against MOXy.

• http://bugs.eclipse.org/395301

---

WORKAROUND

You can make the property of type Integer instead of int. Or better yet just set the type property on the @XmlElement annotation to be Integer. Any type capable of holding a null value will be optional by default.

Config

package forum13595629;

import java.io.Serializable;
import javax.xml.bind.annotation.*;

@XmlRootElement(name = "appConfig")
@XmlType(propOrder = {})
public class Config implements Serializable {

    private int advancedFooBar;

    @XmlElement(name = "advancedfoobar", type=Integer.class)
    public int getAdvancedFooBar() {
        return advancedFooBar;
    }

    public void setAdvancedFooBar(int advancedFooBar) {
        this.advancedFooBar = advancedFooBar;
    }

}

Demo

package forum13595629;

import java.io.IOException;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.SchemaOutputResolver;
import javax.xml.transform.Result;
import javax.xml.transform.stream.StreamResult;

public class Demo {

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

        jc.generateSchema(new SchemaOutputResolver() {

            @Override
            public Result createOutput(String namespaceUri,
                    String suggestedFileName) throws IOException {
                StreamResult result = new StreamResult(System.out);
                result.setSystemId(suggestedFileName);
                return result;
            }

        });

    }

}

Output

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
   <xsd:complexType name="config">
      <xsd:all>
         <xsd:element name="advancedfoobar" type="xsd:int" minOccurs="0"/>
      </xsd:all>
   </xsd:complexType>
   <xsd:element name="appConfig" type="config"/>
</xsd:schema>