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POnot nillable yet required and null value
 

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    <p>I just found a curious case of JAXB with my colleague.</p> <p>I declared a field with <code>@XmlElement(required = true)</code> which is <code>nillable = false</code> as default.</p> <p>But I, by accident, tried to marshall an instance with the value of null.</p> <p>And I saw that the element is just omitted. Is it normal? Is it just a programmer's fault?</p> <pre class="lang-java prettyprint-override"><code>import java.io.*; import javax.xml.bind.*; import javax.xml.bind.annotation.*; import javax.xml.transform.*; import javax.xml.transform.stream.*; @XmlAccessorType(XmlAccessType.NONE) @XmlRootElement public class Doughan { public static void main(final String[] args) throws JAXBException, IOException { final JAXBContext context = JAXBContext.newInstance(Doughan.class); final Marshaller marshaller = context.createMarshaller(); marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE); System.out.println("\n------------------------------------- not valid, is it?"); marshaller.marshal(new Doughan(), System.out); System.out.println("\n------------------------------------------------- valid"); marshaller.marshal(new Doughan("Blaise"), System.out); System.out.println("\n------------------------------------------------ schema"); context.generateSchema(new SchemaOutputResolver(){ @Override public Result createOutput(final String namespaceUri, final String suggestedFileName) throws IOException { return new StreamResult(System.out) { @Override public String getSystemId() { return "Do I really have to do this?"; } }; } }); } public Doughan() { this(null); } public Doughan(final String name) { super(); this.name = name; } @XmlElement(required = true) // default; nillable = false private String name; @XmlElement(nillable = true, required = true) private String nill = null; } </code></pre> <p>Here comes what I got.</p> <pre class="lang-xml prettyprint-override"><code>------------------------------------- not valid, is it? &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;doughan&gt; &lt;nill xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/&gt; &lt;/doughan&gt; -------------------------------------- valid, isn't it? &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;doughan&gt; &lt;name&gt;Blaise&lt;/name&gt; &lt;nill xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/&gt; &lt;/doughan&gt; ------------------------------------------------ schema &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt; &lt;xs:element name="doughan" type="doughan"/&gt; &lt;xs:complexType name="doughan"&gt; &lt;xs:sequence&gt; &lt;xs:element name="name" type="xs:string"/&gt; &lt;xs:element name="nill" type="xs:string" nillable="true"/&gt; &lt;/xs:sequence&gt; &lt;/xs:complexType&gt; &lt;/xs:schema&gt; </code></pre> <p>xmllint</p> <pre><code>$ head -n100 doughan.xsd doughan1.xml doughan2.xml ==&gt; doughan.xsd &lt;== &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt; &lt;xs:element name="doughan" type="doughan"/&gt; &lt;xs:complexType name="doughan"&gt; &lt;xs:sequence&gt; &lt;xs:element name="name" type="xs:string"/&gt; &lt;xs:element name="nill" type="xs:string" nillable="true"/&gt; &lt;/xs:sequence&gt; &lt;/xs:complexType&gt; &lt;/xs:schema&gt; ==&gt; doughan1.xml &lt;== &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;doughan&gt; &lt;nill xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/&gt; &lt;/doughan&gt; ==&gt; doughan2.xml &lt;== &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;doughan&gt; &lt;name&gt;Blaise&lt;/name&gt; &lt;nill xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/&gt; &lt;/doughan&gt; $ xmllint --schema doughan.xsd doughan1.xml &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;doughan&gt; &lt;nill xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/&gt; &lt;/doughan&gt; Element 'nill': This element is not expected. Expected is ( name ). doughan1.xml fails to validate $ xmllint --schema doughan.xsd doughan2.xml &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt; &lt;doughan&gt; &lt;name&gt;Blaise&lt;/name&gt; &lt;nill xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/&gt; &lt;/doughan&gt; doughan2.xml validates $ </code></pre> <p>With respects.</p>
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    1. USJin Kwon
    1. USJin Kwon
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      1. POnot nillable yet required and null value
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      1. POnot nillable yet required and null value
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