如何通过 jaxb 从生成的 XML 中删除不需要的元素

Question

I want to know if there is anyway for removing not required elements from generated xml using jaxb.I have my xsd element definition as follows.

           <xsd:element name="Title" maxOccurs="1" minOccurs="0">
                <xsd:annotation>
                    <xsd:documentation>
                        A name given to the digital record.
                    </xsd:documentation>
                </xsd:annotation>
                <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                        <xsd:minLength value="1"></xsd:minLength>
                    </xsd:restriction>
                </xsd:simpleType>
            </xsd:element>

As you can see it is not a mandatory element because

minOccurs="0"

But if it is not empty the length should be 1.

<xsd:minLength value="1"></xsd:minLength>

At the time of marshalling if I left the Title field blank it is throwing the SAXException because of min-length restriction. So what I want to do is to remove the whole occurrence of <Title/> from generated XML.Right now i have removed the min-length restriction so it is adding the <Title> element as EMPTY

<Title></Title>

But I do not want it like this.Any help is appreciated.I am using jaxb 2.0 for Marshalling.

UPDATE:

Following is my variable definiton :

  private JAXBContext jaxbContext;
    private Unmarshaller unmarshaller;
    private SchemaFactory factory;
    private Schema schema;
    private Marshaller marshaller;

Marshalling code.

            jaxbContext = JAXBContext.newInstance(ERecordType.class);
            marshaller = jaxbContext.createMarshaller();
            factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
            schema = factory.newSchema((new File(xsdLocation)));
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            ERecordType e = new ERecordType();
            e.setCataloging(rc);
            /**
             * Validate Against Schema.
             */
            marshaller.setSchema(schema);
            /**
             * Marshal will throw an exception if XML not validated against
             * schema.
             */
            marshaller.marshal(e, System.out);

Answer 1

如果您将 title 值设置为空字符串""它会生成<Title/> ，如果您将它设置为null它应该完全省略该元素。

Answer 2

I'm exploiting the XmlAdapter, implementing a transparent adapter which return in marshaling the null value if the Collection or String is empty.

public class XMLStringAdapter extends XmlAdapter<String, String> {


    @Override
    public String unmarshal(String v) throws Exception {
        return v;
    }

    @Override
    public String marshal(String v) throws Exception {
        return v != null && v.isEmpty() ? null : v;
    }
}

Also add in package-info.java

@XmlJavaTypeAdapters({
@XmlJavaTypeAdapter(value=StringAdapter.class, type=String.class)
})
your.package

https://www.eclipse.org/eclipselink/documentation/2.6/moxy/advanced_concepts006.htm

How can JAXB XmlAdapter be used to marshall lists?