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  2. NPE when using MOXy's meta data with a class that implements java.util.Map

NPE when using MOXy's meta data with a class that implements java.util.Map

由 冷暖自知 提交于 2019-12-01 19:31:10

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

This is a very interesting use case. JAXB (JSR-222) has representations for maps and domain objects, so it is intersting to consider how a hybrid object should behave. I have added the following enhancement request to introduce support for it:

UPDATE

We have just finished implementing this enhancement. You can try it out using an EclipseLink 2.4.0 nightly download start on April 19, 2012 from the following location:

The fix involves leveraging the super-type property to specify a super type to override the real super type. The super-type property was previously only leveraged by our dynamic JAXB support.

bindings.xml

<?xml version="1.0"?>
<xml-bindings 
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="forum10075634">
    <java-types>
        <java-type name="SampleClassA" super-type="java.lang.Object" xml-accessor-type="NONE">
            <xml-root-element name="SAMPLE" />
            <java-attributes>
                <xml-attribute java-attribute="someProperty" name="SomeProperty" required="true"/>
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

DelegatedMap

Below is an implementation of the DelegatatedMap class as described in your question.

package forum10075634;

import java.util.*;

public class DelegatedMap<K,V> implements Map<K,V> {

    private Map<K,V> map;

    public DelegatedMap() {
        map = new HashMap<K,V>();
    }

    public DelegatedMap(Map<K,V> map) {
        this.map = map;
    }

    public void clear() {
        map.clear();
    }

    public boolean containsKey(Object key) {
        return map.containsKey(key);
    }

    public boolean containsValue(Object value) {
        return map.containsValue(value);
    }

    public Set<java.util.Map.Entry<K, V>> entrySet() {
        return map.entrySet();
    }

    public V get(Object key) {
        return map.get(key);
    }

    public boolean isEmpty() {
        return map.isEmpty();
    }

    public Set<K> keySet() {
        return map.keySet();
    }

    public V put(K key, V value) {
        return map.put(key, value);
    }

    public void putAll(Map<? extends K, ? extends V> m) {
        map.putAll(m);
    }

    public V remove(Object key) {
        return map.remove(key);
    }

    public int size() {
        return map.size();
    }

    public Collection<V> values() {
        return map.values();
    }

}

SampleClassA

package forum10075634;

import java.util.Map;

public class SampleClassA extends DelegatedMap<String, Object> {

    public SampleClassA() {
        super();
    }

    public SampleClassA(Map<String, Object> m) {
        super(m);
    }

    public void setSomeProperty(String value) {
        put("somevalue", value);
    }

    public String getSomeProperty() {
        return (String) get("somevalue");
    }

}

jaxb.properties

To specify MOXy as your JAXB provider you need to add a file called jaxb.properties in the same package as your domain classes with the following entry:

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

Demo

package forum10075634;

import java.io.StringReader;
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, "forum10075634/bindings.xml");
        JAXBContext jc = JAXBContext.newInstance(new Class[] {SampleClassA.class}, properties);

        StringReader xml = new StringReader("<SAMPLE SomeProperty='Foo'/>");
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        SampleClassA sampleClassA = (SampleClassA) unmarshaller.unmarshal(xml);

        System.out.println(sampleClassA.getSomeProperty());
        System.out.println(sampleClassA.get("somevalue"));

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

}

Output

Foo
Foo
<?xml version="1.0" encoding="UTF-8"?>
<SAMPLE SomeProperty="Foo"/>
标签
java
map
jaxb
moxy
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