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Difference between revisions of "EclipseLink/UserGuide/MOXy/Mapping the Unmappable/XML Transformations"

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{{EclipseLink_UserGuide
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See http://www.eclipse.org/eclipselink/documentation/2.4/moxy/advanced_concepts007.htm
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|info=y
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|eclipselink=y
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|eclipselinktype=MOXy
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}}
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=Transformation Mapping=
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In many cases, you can use MOXy's transformation mapping ('''@XmlTransformation''') to map an unmapple object in JAXB.
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For example, if you wanted to map the following XML to objects and combine the values of '''DATE''' and '''TIME''' into a single '''java.util.Date''' object, you can use a transformation mapping.
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<souce lang="xml">
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<ELEM_B>
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    <B_DATE>20100825</B_DATE>
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    <B_TIME>153000</B_TIME>
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    <NUM>123</NUM>
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    <C_DATE>20100825</C_DATE>
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    <C_TIME>154500</C_TIME>
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</ELEM_B>
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</source>
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'''Note:''' Ordinarily, you would use '''@XmlAdapter'''. However:
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* Although the '''DATE/TIME''' pairings are repeated throughout the document, the element name changes ''each time'' (such as '''B_DATE/B_TIME''', '''C_DATE/C_TIME''', and so on).
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* Because each pairing is missing a grouping element, you would need to adapt ''the entire'' '''ElemB''' class.
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In this case the transformation mapping concept in MOXy will make this use case much easier to map.  Let's look at how this looks:
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<source lang="Java">
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import java.util.Date;
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import javax.xml.bind.annotation.XmlAccessType;
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import javax.xml.bind.annotation.XmlAccessorType;
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import javax.xml.bind.annotation.XmlElement;
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import javax.xml.bind.annotation.XmlRootElement;
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import org.eclipse.persistence.oxm.annotations.XmlReadTransformer;
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import org.eclipse.persistence.oxm.annotations.XmlTransformation;
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import org.eclipse.persistence.oxm.annotations.XmlWriteTransformer;
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import org.eclipse.persistence.oxm.annotations.XmlWriteTransformers;
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@XmlAccessorType(XmlAccessType.FIELD)
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@XmlRootElement(name="ELEM_B")
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public class ElemB {
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    @XmlReadTransformer(transformerClass=DateAttributeTransformer.class)
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    @XmlWriteTransformers({
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        @XmlWriteTransformer(xmlPath="B_DATE/text()", transformerClass=DateFieldTransformer.class),
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        @XmlWriteTransformer(xmlPath="B_TIME/text()", transformerClass=TimeFieldTransformer.class),
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    })
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    private Date bDate;
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    @XmlElement(name="NUM")
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    private int num;
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    @XmlReadTransformer(transformerClass=DateAttributeTransformer.class)
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    @XmlWriteTransformers({
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        @XmlWriteTransformer(xmlPath="C_DATE/text()", transformerClass=DateFieldTransformer.class),
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        @XmlWriteTransformer(xmlPath="C_TIME/text()", transformerClass=TimeFieldTransformer.class),
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    })
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    private Date cDate;
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}
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</source>
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XML Read Transformer
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An XML read transformer is responsible for constructing the object value from XML.
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import java.text.ParseException;
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import java.text.SimpleDateFormat;
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import org.eclipse.persistence.internal.helper.DatabaseField;
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import org.eclipse.persistence.mappings.foundation.AbstractTransformationMapping;
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import org.eclipse.persistence.mappings.transformers.AttributeTransformer;
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import org.eclipse.persistence.sessions.Record;
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import org.eclipse.persistence.sessions.Session;
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public class DateAttributeTransformer implements AttributeTransformer {
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    private AbstractTransformationMapping mapping;
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    private SimpleDateFormat yyyyMMddHHmmss = new SimpleDateFormat("yyyyMMddHHmmss");
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    public void initialize(AbstractTransformationMapping mapping) {
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        this.mapping = mapping;
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    }
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    public Object buildAttributeValue(Record record, Object instance, Session session) {
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        try {
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            String dateString = null;
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            String timeString = null;
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            for(DatabaseField field : mapping.getFields()) {
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                if(field.getName().contains("DATE")) {
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                    dateString = (String) record.get(field);
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                } else {
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                    timeString = (String) record.get(field);
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                }
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            }
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            return yyyyMMddHHmmss.parseObject(dateString + timeString);
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        } catch(ParseException e) {
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            throw new RuntimeException(e);
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        }
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    }
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}
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XML Write Transformer(s)
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An XML write transformer is responsible for constructing an XML value from the object.  A transformation mapping may have multiple write transformers.  For this example we will have two.
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The first XML write transformer is responsible for writing out the year, month, and day information in the format yyMMdd.
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import java.text.SimpleDateFormat;
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import java.util.Date;
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import org.eclipse.persistence.mappings.foundation.AbstractTransformationMapping;
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import org.eclipse.persistence.mappings.transformers.FieldTransformer;
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import org.eclipse.persistence.sessions.Session;
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public class DateFieldTransformer implements FieldTransformer {
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    private AbstractTransformationMapping mapping;
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    private SimpleDateFormat yyyyMMdd = new SimpleDateFormat("yyyyMMdd");
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    public void initialize(AbstractTransformationMapping mapping) {
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        this.mapping = mapping;
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    }
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    public Object buildFieldValue(Object instance, String xPath, Session session) {
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        Date date = (Date) mapping.getAttributeValueFromObject(instance);
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        return yyyyMMdd.format(date);
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    }
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}
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The second XML write transformer is responsible for writing out the hour, minute, and second information in the format HHmmss.
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import java.text.SimpleDateFormat;
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import java.util.Date;
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import org.eclipse.persistence.mappings.foundation.AbstractTransformationMapping;
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import org.eclipse.persistence.mappings.transformers.FieldTransformer;
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import org.eclipse.persistence.sessions.Session;
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public class TimeFieldTransformer implements FieldTransformer {
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    private AbstractTransformationMapping mapping;
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    private SimpleDateFormat HHmmss = new SimpleDateFormat("HHmmss");
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    public void initialize(AbstractTransformationMapping mapping) {
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        this.mapping = mapping;
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    }
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    public Object buildFieldValue(Object instance, String xPath, Session session) {
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        Date date = (Date) mapping.getAttributeValueFromObject(instance);
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        return HHmmss.format(date);
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    }
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}
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jaxb.properties
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In order to use the MOXy JAXB implementation you need to add a jaxb.properties file in which your model classes with the following entry:
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javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory
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Demo
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The following class can be used to demonstrate the mapping:
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import java.io.File;
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import javax.xml.bind.JAXBContext;
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import javax.xml.bind.Marshaller;
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import javax.xml.bind.Unmarshaller;
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public class Demo {
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    public static void main(String[] args) throws Exception {
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        JAXBContext jc = JAXBContext.newInstance(ElemB.class);
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        Unmarshaller unmarshaller = jc.createUnmarshaller();
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        File xml = new File("input.xml");
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        ElemB elemB = (ElemB) unmarshaller.unmarshal(xml);
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        Marshaller marshaller = jc.createMarshaller();
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        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
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        marshaller.marshal(elemB, System.out);
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    }
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}
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Please Note
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{{EclipseLink_MOXy
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|next=    [[EclipseLink/UserGuide/MOXy/Mapping_the_Unmappable/XMLFragmentMapping|XML Fragment mapping]]
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|previous= [[EclipseLink/UserGuide/MOXy/Mapping_the_Unmappable/Converters|Converters]]
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|up =      [[EclipseLink/UserGuide/MOXy/Mapping_the_Unmappable|Mapping the Unmappable]]
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|version=2.2.0 - DRAFT}}
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Latest revision as of 10:33, 8 November 2012

See http://www.eclipse.org/eclipselink/documentation/2.4/moxy/advanced_concepts007.htm

Retrieved from "https://wiki.eclipse.org/index.php?title=EclipseLink/UserGuide/MOXy/Mapping_the_Unmappable/XML_Transformations&oldid=321321"

This page was last modified 10:33, 8 November 2012 by Rick Sapir. Based on work by Rick Barkhouse and Blaise Doughan.

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