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=Default Root Element= | =Default Root Element= | ||
You configure a default root element so that the EclipseLink runtime knows the data source data type associated with the class the descriptor describes. | You configure a default root element so that the EclipseLink runtime knows the data source data type associated with the class the descriptor describes. |
Revision as of 14:47, 6 January 2011
EclipseLink MOXy
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Key API
Contents
Default Root Element
You configure a default root element so that the EclipseLink runtime knows the data source data type associated with the class the descriptor describes.
Note: The undefined document root element of a referenced object is ignored during marshalling with an any collection mapping and object mapping.
This section describes what a default root element is and how EclipseLink uses it.
Consider the Customer and Address classes and their mappings, shown in this example:
Customer and Address Classes
Class: Customer Default Root: customer Attributes and Mappings: name:String Direct Mapping to name/text() billingAddress:Address Composite Object Mapping to billing-address shippingAddress:Address Composite Object Mapping to shipping-address Class: Address Default Root: address Attributes and Mappings: street:String Direct Mapping to street/text() city:String Direct Mapping to city/text()
These classes correspond to the XML schema, shown in this example.
Customer and Address Schema
<xsd:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xsd:complexType name="address-type"> <xsd:sequence> <element name="street" type="xsd:string"/> <element name="city" type="xsd:string"/> </xsd:sequence> </xsd:complexType> <xsd:element name="customer" type="customer-type"/> <xsd:complexType name="customer-type"> <xsd:sequence> <xsd:element name="name" type="xsd:string"/> <xsd:element name="billing-address" type="address-type"/> <xsd:element name="shipping-address" type="address-type"/> </xsd:sequence> </xsd:complexType> </xsd:schema>
When an instance of the Customer class is persisted to XML, the EclipseLink runtime performs the following:
- Gets the default root element.The Customer class instance corresponds to the root of the XML document. The EclipseLink runtime uses the default root element specified on the descriptor (customer) to start the XML document. EclipseLink then uses the mappings on the descriptor to marshal the object's attributes:
<customer> <name>…</name> </customer>
- When the EclipseLink runtime encounters an object attribute such as billingAddress, it checks the mapping associated with it to determine with what element (billing-address) to continue:
<customer> <name>…</name> <billing-address/> </customer>
The EclipseLink runtime checks the mapping's reference descriptor (Address) to determine what attributes to persist:<customer> <name>…</name> <billing-address> <street>…</street> <city>…</city> </billing-address> </customer>