Java到XML Castor的映射

Question

I am trying to map a POJO to an xml. Now the POJO consists of some attributes which are basic String/Integer etc and some which are other POJO classes. The xml mapping file that I am attempting to create, I want an xml element at the top level to be populated with a java attribute that is 2 levels deep.

for example, if I have 2 java class `

class classA{

private ClassB var1
private String var2

}

class classB{
private ClassC var3;
}

class classC{
private String var4;
}

Now my xml mapping looks like

CruiseLine Mapping

<class name="ClassA"
    auto-complete="false"
>
    <map-to xml="Sample" />
    <field name="var2">
        <bind-xml node="attribute" name="var2" />
    </field>
    <field name="var4 from classC">
        <I want a mapping for the var4 from classC to appear here. How do I do that ?>
</class>

` As you see, I want the mapping for var4 from classC in the xml element Sample. I want it to be an element of the sample element.

`

<Sample var2="value">
     <data var4="var4 value">
</Sample>

`

Help appreciated !

Answer 1

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB 2 (JSR-222) expert group.

Blaise : I have not used EclipseLink before, however I think I can move out of castor if it is relatively simple to adopt EclipseLink ? Its just that the entire project has been using Castor so it would be more consistent. However, could you please elaborate on Eclipselink. Thanks. – TYS

EclipseLink MOXy is a JAXB (JSR-222) implementation. Looking at your question, this model can be mapped to the desired XML using any JAXB implementation as follows:

ClassA

package forum9994762;

import javax.xml.bind.annotation.*;

@XmlRootElement(name="Sample")
@XmlAccessorType(XmlAccessType.FIELD)
public class ClassA {

    @XmlElement(name="data")
    private ClassB var1;

    @XmlAttribute
    private String var2;

}

ClassB

package forum9994762;

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
public class ClassB {

    @XmlAttribute(name="var4")
    private ClassC var3;

}

ClassC

package forum9994762;

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
public class ClassC {

    @XmlValue
    private String var4;

}

Demo

package forum9994762;

import java.io.File;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(ClassA.class);

        File xml = new File("src/forum9994762/input.xml");
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        ClassA classA = (ClassA) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(classA, System.out);
    }

}

input.xml/Output

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Sample var2="value">
    <data var4="var4 value"/>
</Sample>

---

Mapping File

As a Castor user, you may prefer representing your metadata as an external mapping file. EclipseLink MOXy offers such an extension:

binding.xml

<?xml version="1.0" encoding="UTF-8"?>
<xml-bindings
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="forum9994762"
    xml-accessor-type="FIELD">
    <java-types>
        <java-type name="ClassA">
            <xml-root-element name="Sample"/>
            <java-attributes>
                <xml-element java-attribute="var1" name="data"/>
                <xml-attribute java-attribute="var2"/>
            </java-attributes>
        </java-type>
        <java-type name="ClassB">
            <java-attributes>
                <xml-attribute java-attribute="var3" name="var4"/>
            </java-attributes>
        </java-type>
        <java-type name="ClassC">
            <java-attributes>
                <xml-value java-attribute="var4"/>
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

Demo

package forum9994762;

import java.io.File;
import java.util.*;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.JAXBContextFactory;

public class Demo {

    public static void main(String[] args) throws Exception {
        Map<String, Object> properties = new HashMap<String, Object>(1);
        properties.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, "forum9994762/binding.xml");
        JAXBContext jc = JAXBContext.newInstance("forum9994762", ClassA.class.getClassLoader(), properties);

        File xml = new File("src/forum9994762/input.xml");
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        ClassA classA = (ClassA) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(classA, System.out);
    }

}

For More Infomation

• http://blog.bdoughan.com/2010/12/extending-jaxb-representing-annotations.html
• http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html

Answer 2

If you use auto-complete=false in your mapping.xml file for ClassA <class name="ClassA" auto-complete="false" > then you must tell Castor marshaller how to map ClassB and ClassC individually. Including these two lines may help you getting started:

<class name="ClassB" auto-complete="true">
 <map-to xml="class-B" />
</class>
<class name="ClassC" auto-complete="true">
 <map-to xml="class-C" />
</class>

But since var4 is a member of ClassC but not ClassB, it will be one level deep inside your xml output hierarchy.