XJC Java class generation for <xs:choice> element which is not unbounded

问题

After this similar question yesterday I have another question concerning inheritance in XML schema and XJC bindings.

Given the following choice element such that Book and Journal have a common parent type (Publication).

<xsd:choice >
    <xsd:element name="Book" type="Book" />
    <xsd:element name="Journal" type="Journal" />
</xsd:choice>

The Java class properties which are generated are like:

private Book book;
private Journal journal;

Since <xsd:choice> means that there might be either a Book or a Journal I would prefer

private Publication bookOrJournal;

If I had a list of Publications by setting maxOccurs="unbounded" in the choice element, it would work that way and I would get

private List<Publication> bookOrJournal;

How to achieve this with a non-collection property?

回答1:

You can using the following XJC binding to achieve this.

<xs:complexType name="myClass">
  <xs:sequence>
    <xs:choice>
      <xs:annotation>
        <xs:appinfo>
          <jaxb:property name="bookOrJournal"/>
        </xs:appinfo>
      </xs:annotation>
      <xs:element name="Book" type="Book"/>
      <xs:element name="Journal" type="Journal"/>
    </xs:choice>
  </xs:sequence>
</xs:complexType>

After executing xjc <XSD File> -extension, this generated the following Java class for me.

@XmlElements({
    @XmlElement(name = "Book", type = Book.class),
    @XmlElement(name = "Journal", type = Journal.class)
})
protected Publication bookOrJournal;

To use the XJC binding, I added the following to the top of my XSD.

<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
  xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
  jaxb:version="1.0" jaxb:extensionBindingPrefixes="xjc">

来源：https://stackoverflow.com/questions/10137968/xjc-java-class-generation-for-xschoice-element-which-is-not-unbounded