Difference between revisions of "EclipseLink/UserGuide/MOXy/Simple Values/Special Schema Types/Unions"

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{{EclipseLink_UserGuide
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Please see http://www.eclipse.org/eclipselink/documentation/2.4/moxy/special_schema_types002.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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=Mapping to a Union Field=
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The following XML schema and class diagram show a typical use of an XML Schema Union:
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<source lang="xml">
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<?xml version="1.0" encoding="UTF-8"?>
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<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
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    <xsd:element name="customer" type="customer-type" />
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    <xsd:complexType name="customer-type">
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        <xsd:sequence>
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            <xsd:element name="shoe-size" type="size-type" />
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        </xsd:sequence>
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    </xsd:complexType>
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    <xsd:simpleType name="size-type">
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        <xsd:union memberTypes="xsd:decimal xsd:string" />
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    </xsd:simpleType>
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</xsd:schema>
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</source>
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[[Image:dxmuc.gif]]<br><br>
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The figure below illustrates a mapping to a union field in an XML document that conforms to the example schema. When EclipseLink unmarshalls the XML document, it tries each of the union types until it can make a successful conversion. The first schema type in the union is '''xsd:decimal'''. Because "10.5" is a valid decimal, EclipseLink converts the value to the appropriate type. If the '''Object''' attribute is specific enough to trigger an appropriate value, EclipseLink will use that type instead. Otherwise, EclipseLink uses a default (in this case '''BigDecimal'''). You can override this behavior in Java code.
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[[Image:dxmuv.gif]]<br><br>
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In a second example document, the value "M" is not a valid '''xsd:decimal''' type, so the next union type is tried, '''xsd:string'''.
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[[Image:dxmuvs.gif]]<br><br>
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== Example ==
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Currently, EclipseLink does not support the mapping of Unions using Annotations or OXM Metadata.  However, an EclipseLink XML Customizer can be used to create the mapping.
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First, we annotate the '''shoeSize''' attribute with '''@XmlTransient''', to avoid automatically generating a mapping for it.  We also include an '''@XmlCustomizer''' annotation; the '''CustomerCustomizer''' class will create the Union mapping in code.
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<source lang="java">
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package example;
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import javax.xml.bind.annotation.*;
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import org.eclipse.persistence.oxm.annotations.*;
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@XmlRootElement
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@XmlAccessorType(XmlAccessType.FIELD)
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@XmlCustomizer(EmployeeCustomizer.class)
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public class Customer {
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  @XmlTransient
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  private Object shoeSize;
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  ...
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}
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</source>
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The '''CustomerCustomizer''' class can be used to manually add a mapping to the '''shoeSize''' attribute.  Here, an '''XMLUnionField''' is configured on the mapping, and the possible Union member types are added by calling '''addSchemaType()''':
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<source lang="java">
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package example;
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import org.eclipse.persistence.config.DescriptorCustomizer;
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import org.eclipse.persistence.descriptors.ClassDescriptor;
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import org.eclipse.persistence.oxm.*;
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public class CustomerCustomizer implements DescriptorCustomizer {
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  @Override
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  public void customize(ClassDescriptor descriptor) throws Exception {
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      XMLDirectMapping shoeSizeMapping = new XMLDirectMapping();
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      shoeSizeMapping.setAttributeName("shoeSize");
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      XMLUnionField shoeSizeField = new XMLUnionField();
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      shoeSizeField.setXPath("shoeSize/text()");
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      shoeSizeField.addSchemaType(XMLConstants.DECIMAL_QNAME);
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      shoeSizeField.addSchemaType(XMLConstants.STRING_QNAME);
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      shoeSizeMapping.setField(shoeSizeField);
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      descriptor.addMapping(shoeSizeMapping);
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  }
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}
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</source>
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To override the default conversion, use the '''XMLUnionField''' method '''addConversion''':
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<source lang="java">
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  shoeSizeField.addConversion(XMLConstants.DECIMAL_QNAME, Float.class);
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</source>
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=Mapping to a Union of Lists=
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EclipseLink also supports mapping to lists of Unions, as demonstrated in the following schema:
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<source lang="xml">
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<?xml version="1.0" encoding="UTF-8"?>
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<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
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  <xsd:element name="vacation" type="unionOfLists"/>
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  <xsd:simpleType name="unionOfLists">
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      <xsd:union memberTypes="xsd:double">
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        <xsd:simpleType>
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            <xsd:list itemType="xsd:date"/>
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        </xsd:simpleType>
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        <xsd:simpleType>
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            <xsd:list itemType="xsd:integer"/>
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        </xsd:simpleType>
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      </xsd:union>
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  </xsd:simpleType>
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</xsd:schema>
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</source>
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[[Image:dxuofl.gif]]<br><br>
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Note that in this example, valid XML documents contain either a single '''xsd:double''' value, a list of '''xsd:date''' values, or a list of '''xsd:integer''' values.
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<span id="Example 58-19"></span>
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''''' Java for XML Direct Mapping to Union of Lists'''''
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XMLDirectMapping mapping = new XMLDirectMapping();
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mapping.setAttributeName("vacation");
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mapping.setXPath("UnionOfLists/text()");
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=Mapping to a Union of Unions=
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Given the XML schema in the [[#Example 58-20|Schema for XML Direct Mapping to a Union of Unions]] example, the [[#Figure 58-12|Java Class for XML Direct Mapping to a Union of Unions]] figure illustrates a Java class that can be mapped to a corresponding XML document. The [[#Example 58-21|Java for XML Direct Mapping to a Union of Unions]] example shows how to configure this mapping in Java.
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<span id="Example 58-20"></span>
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''''' Schema for XML Direct Mapping to a Union of Unions'''''
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<?xml version="1.0" encoding="UTF-8"?>
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<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
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    <xsd:element name="vacation" type="unionOfUnions"/>
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    <xsd:simpleType name="unionOfUnions">
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        <xsd:union>
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            <xsd:simpleType>
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                <xsd:union>
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                    <xsd:simpleType>
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                        <xsd:list itemType="xsd:date"/>
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                    </xsd:simpleType>
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                    <xsd:simpleType>
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                        <xsd:list itemType="xsd:integer"/>
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                    </xsd:simpleType>
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                </xsd:union>
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            </xsd:simpleType>
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            <xsd:simpleType>
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                <xsd:union>
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                    <xsd:simpleType>
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                        <xsd:list itemType="xsd:string"/>
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                    </xsd:simpleType>
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                    <xsd:simpleType>
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                        <xsd:list itemType="xsd:float"/>
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                    </xsd:simpleType>
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                </xsd:union>
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            </xsd:simpleType>
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        </xsd:union>
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    </xsd:simpleType>
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</xsd:schema>
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<span id="Figure 58-12"></span>
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''''' Java Class for XML Direct Mapping to a Union of Unions'''''
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[[Image:dxuofu.gif]]<br><br>
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<span id="Example 58-21"></span>
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''''' Java for XML Direct Mapping to a Union of Unions'''''
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XMLDirectMapping vacationMapping = new XMLDirectMapping();
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vacationMapping.setAttributeName("vacation");
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XMLUnionField vacationField = new XMLUnionField();
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vacationField.setXPath("vacation/text()");
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vacationField.addSchemaType(XMLConstants.DATE_QNAME);
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vacationField.addSchemaType(XMLConstants.INTEGER_QNAME);
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vacationField.addSchemaType(XMLConstants.STRING_QNAME);
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vacationField.addSchemaType(XMLConstants.FLOAT_QNAME);
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vacationMapping.setField(vacationField);
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{{EclipseLink_MOXy
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|previous= [[EclipseLink/UserGuide/MOXy/Simple_Values/Special_Schema_Types|Special Schema Types]]
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|up=    [[EclipseLink/UserGuide/MOXy/Simple_Values/Special_Schema_Types|Special Schema Types]]
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|next=      [[EclipseLink/UserGuide/MOXy/Simple_Values/Binary_Types|Binary Types]]
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|version=2.2.0 Draft
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}}
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Latest revision as of 10:19, 8 November 2012

Please see http://www.eclipse.org/eclipselink/documentation/2.4/moxy/special_schema_types002.htm