EclipseLink MOXy: Logical operators in XmlPath annotation

问题

Do logical operators work in XmlPath annotations of EclipseLink MOXy? I tried and could not make it work (no Exception is thrown and nothing is bound to "elements").

For example, I would like to have in a bindings file something like this:

    <java-type name="Content">
        <java-attributes>
           <xml-element java-attribute="elements" xml-path="/a/b/ | /c/d" 
            type="ElementType" container-type="java.util.List" />
        </java-attributes>
    </java-type>

Is there a way to achieve the same result from a modification of the bindings without using the logical or in the xml-path?

I can only think of a workaround where one would use getters and settings in the domain model, bind both /a/b and /c/d to elements and have the setters append elements to the List rather then replacing the list upon each call to setElements(). I'd rather handle it in the bindings file, though.

Does there exist a place in the documentation that specifies which parts of XPath are supported in MOXy?

回答1:

Here is an example of how you could support this use case.

Mapping Document (bindings.xml)

You could use the xml-elements mapping for this use case. On each of the nested xml-element mappings you would specify a different xml-path.

<?xml version="1.0"?>
<xml-bindings 
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="forum17977009">
    <java-types>
        <java-type name="Content">
            <xml-root-element/>
             <java-attributes>
                <xml-elements java-attribute="elements">
                    <xml-element xml-path="a/b"/>
                    <xml-element xml-path="c/d"/>
                </xml-elements>
             </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

Java Model (Content)

Below is the Java model we will use for this example.

package forum17977009;

import java.util.List;

public class Content {

    private List<ElementType> elements;

    public List<ElementType> getElements() {
        return elements;
    }

    public void setElements(List<ElementType> elements) {
        this.elements = elements;
    }


}

jaxb.properties

To specify MOXy as your JAXB provider you include a file called jaxb.properties in the same package as your domain model with the following entry (see: http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html).

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

Input (input.xml)

Below is a sample input document.

<?xml version="1.0" encoding="UTF-8"?>
<content>
    <a>
        <b/>
        <b/>
    </a>
    <c>
        <d/>
        <d/>
    </c>
</content>

Demo

Below is some demo code you can run to prove that everything works:

package forum17977009;

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

public class Demo {

    public static void main(String[] args) throws Exception {
        Map<String, Object> properties = new HashMap<String, Object>(1);
        properties.put(JAXBContextProperties.OXM_METADATA_SOURCE, "forum17977009/bindings.xml");
        JAXBContext jc = JAXBContext.newInstance(new Class[] {Content.class}, properties);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum17977009/input.xml");
        Content content = (Content) unmarshaller.unmarshal(xml);

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

}

Output

Since all of the items are of the same type, they will output based on the xml-path of the first xml-element in the xml-elements mapping:

<?xml version="1.0" encoding="UTF-8"?>
<content>
   <a>
      <b/>
      <b/>
      <b/>
      <b/>
   </a>
</content>

---

UPDATE

Does there exist a place in the documentation that specifies which parts of XPath are supported in MOXy?

Here are some examples that should help:

• http://blog.bdoughan.com/2010/07/xpath-based-mapping.html
• http://blog.bdoughan.com/2011/03/map-to-element-based-on-attribute-value.html
• http://blog.bdoughan.com/2010/09/xpath-based-mapping-geocode-example.html

We are going to add some validation on the XPath statements that are entered for mappings. You can track our progress on this using the following link:

• http://bugs.eclipse.org/397101

来源：https://stackoverflow.com/questions/17977009/eclipselink-moxy-logical-operators-in-xmlpath-annotation