JAXB mapping for a map

Question

Using JAXB, how to map below?

I tried mapping it to a Map, to a list of @XmlRootElement anotated classes and other ways, without success.

Flavio Cysne · Accepted Answer

The java.util.Map interface has no provider to marshal/unmarshal its instances. You'll have to write a class that extends XmlAdapter and annotate the java.util.Map attribute with @XmlJavaTypeAdapter(MyMapAdapter.class).

After a while on Google looking for jax-rs java.util.map, I ended up with the codes bellow. In my case I have named my adapter as XmlStringMapAdapter instead of MyMapAdapter.

ServiceDefinition.java

@XmlRootElement(name = "entry")
@XmlAccessorType(XmlAccessType.FIELD)
public class ServiceDefinition {

    @XmlAttribute
    private String key;

    @XmlJavaTypeAdapter(XmlStringMapAdapter.class)
    private Map map = new HashMap();

    // getters & setters
}

EntryElement.java

public class EntryElement {

    @XmlAttribute public String key;
    @XmlAttribute public String value;

    public EntryElement() {}

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

MapElement.java

@XmlRootElement(name = "map")
public class MapElement {

    @XmlElement(name = "entry")
    public List entries = new ArrayList();

    public void addEntry(String key, String value) {
        entries.add(new EntryElement(key, value));
    }

}

XmlStringMapAdapter.java

public class XmlStringMapAdapter extends XmlAdapter> {

    @Override
    public MapElement marshal(Map v) throws Exception {

        if (v == null || v.isEmpty()) {return null;}

        MapElement map = new MapElement();

        for (String key : v.keySet()) {
            map.addEntry(key, v.get(key));
        }

        return map;
    }

    @Override
    public Map unmarshal(MapElement v) throws Exception {
        if (v == null) {return null;}

        Map map = new HashMap(v.entries.size());

        for(EntryElement entry: v.entries) {
            map.put(entry.key, entry.value);
        }

        return map;
    }

}

And bellow is a class that I used to test the new map adapter.

ServiceResouce.java

@Path("service")
public class ServiceResource {

    @Context
    private UriInfo uriInfo;

    @GET
    @Path("definition")
    @Produces("application/xml")
    public Response getDefinition() {
        ServiceDefinition def = new ServiceDefinition();
        UriBuilder b = uriInfo.getBaseUriBuilder();

        def.setKey("childResources");
        def.getMap().put("ab/cd", b.path("ab/cd").build(this).getPath());
        def.getMap().put("xx", b.path("xx").build(this).getPath());

        return Response.ok(def).build();
    }
}

Output from the resource above is as shown bellow.

JAXB mapping for a map

Answers (2)

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