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| − | {{EclipseLink_UserGuide
| + | Please see http://www.eclipse.org/eclipselink/documentation/2.4/moxy/type_level003.htm |
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| − | |toc=y
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| − | |eclipselink=y
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| − | |eclipselinktype=MOXy
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| − | }}
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| − | = Handling Inheritance =
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| − | EclipseLink MOXy provides several ways to represent your inheritance hierarchy in XML.
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| − | == Using xsi:type ==
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| − | By default, EclipseLink will use the '''xsi:type''' attribute to represent inheritance in XML.
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| − | In this example an abstract super class ('''ContactInfo''') contains all types of contact information. '''Address''' and '''PhoneNumber''' are the concrete implementations of '''ContactInfo'''.
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| − | <source lang="java">
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| − | public abstract class ContactInfo {
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| − | }
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| − | public class Address extends ContactInfo {
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| − |
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| − | private String street;
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| − | ...
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| − | }
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| − | public class PhoneNumber extends ContactInfo {
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| − | private String number;
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| − | ...
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| − | }
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| − | </source>
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| − | Because the '''Customer''' object can have different types of contact information, its property refers to the superclass.
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| − | <source lang="java">
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| − | @XmlRootElement
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| − | public class Customer {
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| − | private ContactInfo contactInfo;
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| − | ...
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| − | }
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| − | </source>
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| − | Marshalling an example '''Customer''' would produce the following XML:
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| − | <source lang="xml">
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| − | <customer>
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| − | <contactInfo
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| − | xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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| − | xsi:type="address">
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| − | <street>323 Main Street</street>
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| − | </contactInfo>
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| − | </customer>
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| − | </source>
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| − | Note the '''xsi:type''' attribute on the '''contactInfo''' element.
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| − | == Using Substitution Groups ==
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| − | Another way to model inheritance in XML is through XML Schema's ''substitution groups'' functionality. Using this approach, the element name itself determines which subclass to use.
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| − | Taking the same example from above, we will add '''@XmlRootElement''' annotations to each of the subclasses, which will act as the inheritance indicator.
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| − | <source lang="java">
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| − | public abstract class ContactInfo {
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| − | }
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| − | @XmlRootElement
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| − | public class Address extends ContactInfo {
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| − |
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| − | private String street;
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| − | ...
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| − |
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| − | }
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| − | @XmlRootElement
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| − | public class PhoneNumber extends ContactInfo {
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| − | | + | |
| − | private String number;
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| − | ...
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| − |
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| − | }
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| − | </source>
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| − | Using this approach, marshalling an example '''Customer''' would produce the following XML:
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| − | <source lang="xml">
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| − | <customer>
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| − | <address>
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| − | <street>323 Main Street</street>
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| − | </address>
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| − | </customer>
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| − | </source>
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| − | Note that the '''Address''' object is marshalled to the '''address''' element.
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| − | == Using @XmlDescriminatorNode / @XmlDescrimintatorValue ==
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| − | You can also use the MOXY-specific '''@XmlDescriminatorNode''' and '''@XmlDescrimintatorValue''' annotations available in EclipseLink 2.2 to represent inheritance. With this approach, you can select the attribute to represent the subtype.
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| − | Using the same example from above, the '''ContactInfo''' class uses the '''@XmlDescriminatorNode''' annotation to specify the XML attribute ('''classifier''') that will hold the subclass indicator. '''Address''' and '''PhoneNumber''' are annotated with '''@XmlDescriminatorValue''', indicating that class' indicator name ('''address-classifier''' and '''phone-number-classifier''').
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| − | <source lang="java">
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| − | @XmlDiscriminatorNode("@classifier")
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| − | public abstract class ContactInfo {
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| − | }
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| − | @XmlDiscriminatorValue("address-classifier")
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| − | public class Address extends ContactInfo {
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| − |
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| − | private String street;
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| − | ...
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| − |
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| − | }
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| − | @XmlDiscriminatorValue("phone-number-classifier")
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| − | public class PhoneNumber extends ContactInfo {
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| − | | + | |
| − | private String number;
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| − | ...
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| − |
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| − | }
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| − | </source>
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| − | An example '''Customer''' would then produce the following The above sample produces the following XML:
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| − | <source lang="xml">
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| − | <customer>
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| − | <contactInfo classifier="address-classifier">
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| − | <street>323 Main Street</street>
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| − | </contactInfo>
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| − | </customer>
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| − | </source>
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| − | Notice that '''Address''' is marshalled to the '''contactInfo''' element. Its '''classifier''' attribute contains the discriminator node value '''address-classifier'''.
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| − | {{EclipseLink_MOXy
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| − | |next= [[/EclipseLink/UserGuide/MOXy/Simple_Values|Simple Values]]
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| − | |previous= n
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| − | |up= [[EclipseLink/UserGuide/MOXy|MOXy User Guide]]
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| − | |version=2.2.0 DRAFT}}
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