Question

I’m trying to work with JAXB and @XmlJavaTypeAdaptor to map a Map during marshalling. The only issue I’m having is that the “item” element that is used to contain each entry in the map is given a blank namespace.

Below is an example generated XML document that shows the issue:

<format xmlns="myNamespace">
    <data>
        <item xmlns:ns2="myNamespace" xmlns="">
            <ns2:key>Admin</ns2:key>
            <ns2:value>John</ns2:value>
        </item>
    </data>
</format>

I would like the fragment to look like this:

<format xmlns="myNamespace">
    <data>
        <item>
            <key>Admin</key>
            <value>John</value>
        </item>
    </data>
</format>

I’ve simplifed the real-life example to narrow it down to just this case. Here is the class that is being marshalled:

@XmlRootElement(name = "format")
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType
public final class Format {

    @XmlTransient
    private final Map<String, String> data = new HashMap<String, String>();

    @XmlJavaTypeAdapter(MapAdapter.class)
    public Map<String, String> getData() {
        return data;
    }
}

Here is the implementation of XmlAdapter I am using:

public class MapAdapter extends XmlAdapter<MapElements[], Map<String, String>> {

    @Override
    public MapElements[] marshal(Map<String, String> stringStringMap) throws Exception {
        MapElements[] mapElements = new MapElements[stringStringMap.size()];
        int i = 0;

        for (Map.Entry<String, String> entry: stringStringMap.entrySet()) {
            mapElements[i++] = new MapElements(entry.getKey(), entry.getValue());
        }

        return mapElements;
    }

    @Override
    public Map<String, String> unmarshal(MapElements[] mapElements) throws Exception {
        Map<String, String> map = new HashMap<String, String>();

        for (MapElements mapElement : mapElements) {
            map.put(mapElement.key, mapElement.value);
        }

        return map;
    }
}

I set the package level information like so, this does help in that it ensures the namespace for all elements except the “item” elements have the namespace “myNamespace”:

@XmlSchema(namespace = "myNamespace", elementFormDefault = XmlNsForm.QUALIFIED)
package org.prystasj;

import javax.xml.bind.annotation.XmlNsForm;
import javax.xml.bind.annotation.XmlSchema;

I’ve tried every combination of annotation, e.g. @XmlElement(namespace=”myNamespace”), I can think of throughout and there is no chance, so I think I’m missing something conceptual (or maybe even something rather trivial).

I’m using JAXB 2.2.2.

Thanks in advance for any insight.

Answer 1

You could use the following for your XmlAdapter

import java.util.*;

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class MapAdapter extends XmlAdapter<MapAdapter.MapElements, Map<String, String>> {

    @Override
    public MapElements marshal(Map<String, String> stringStringMap) throws Exception {
        MapElements mapElements = new MapElements();
        for (Map.Entry<String, String> entry: stringStringMap.entrySet()) {
            mapElements.item.add(new MapElement(entry.getKey(), entry.getValue()));
        }
        return mapElements;
    }

    @Override
    public Map<String, String> unmarshal(MapElements mapElements) throws Exception {
        Map<String, String> map = new HashMap<String, String>();
        for (MapElement mapElement : mapElements.item) {
            map.put(mapElement.key, mapElement.value);
        }
        return map;
    }

    public static class MapElements {
        public List<MapElement> item = new ArrayList<MapElement>();
    }

    public static class MapElement {
        public String key;
        public String value;

        public MapElement() {
        }

        public MapElement(String key, String value) {
            this.key = key;
            this.value = value;
        }

    }

}