An International Purchase Order Instance Document

HydraExpress XML Binding Development Guide

6.3 An International Purchase Order Instance Document

We begin with a simple instance document.

<ipo:purchaseOrder xmlns:ipo="http://www.example.com/IPO" 
  orderDate="1999-12-05">
  <shipTo exportCode="1" xsi:type="ipo:UKAddress" 
       xmlns:xsd="http://www.w3.org/2001/XMLSchema"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <name>Helen Zoe</name>
    <street>47 Eden Street</street>
    <city>Cambridge</city>
    <postcode>CB1 1JR</postcode>
  </shipTo>
  <billTo xsi:type="ipo:USAddress" 
      xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <name>Robert Smith</name>
    <street>8 Oak Avenue</street>
    <city>Old Town</city>
    <state>PA</state>
    <zip>95819</zip>
  </billTo>
  <items>
    <item partNum="833-AA">
      <productName>Lapis necklace</productName>
      <quantity>1</quantity>
      <USPrice>99.95</USPrice>
      <ipo:comment>Want this for the holidays!</ipo:comment>
      <shipDate>1999-12-05</shipDate>
    </item>
  </items>
</ipo:purchaseOrder>

The instance document contains a billTo element. As you can see from the schema in the preceding section, a billTo is an Address. The Address type has two extensions, USAddress and UKAddress, and a billTo element can be either of these types. Elements with substitutable types are required to have an xsi:type attribute that clarifies the actual type of the element.

When unmarshaling an instance document that contains substitutable elements, HydraExpress uses the xsi:type attribute to determine the correct class type to create. In your application code, you can use the class getTypeId() method to determine its type.

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