JAXB Marshal and Unmarshal Map to/from <key>value</key> - dictionary

Question

I'm trying to marshal and unmarshal Map to/from value pairs. I can marshal the object successfully, however, I cannot unmarshal it from the xml. The unmarshal result is the key exist in the Map, however, its value is null.
Here's the model I want to marshal and unmarshal:
import java.util.Map;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
#XmlRootElement(name="TestModel")
#XmlAccessorType(XmlAccessType.FIELD)
public class TestModel {
#XmlElement(name="Name")
private String name;
#XmlJavaTypeAdapter(MapAdapter.class)
private Map<String, String> metadata;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Map<String, String> getMetadata() {
return metadata;
}
public void setMetadata(Map<String, String> metadata) {
this.metadata = metadata;
}
}
I create a Map Adapter for marshal and unmarshal like below:
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.namespace.QName;
import org.w3c.dom.Element;
public class MapAdapter extends XmlAdapter<MapWrapper, Map<String, String>> {
#Override
public MapWrapper marshal(Map<String, String> m) throws Exception {
MapWrapper wrapper = new MapWrapper();
List<JAXBElement<String>> elements = new ArrayList<JAXBElement<String>>();
if (m != null && !m.isEmpty()) {
for (Entry<String, String> property : m.entrySet()) {
elements.add(new JAXBElement<String>(new QName(property.getKey()),
String.class, property.getValue().toString()));
}
}
wrapper.elements = elements;
return wrapper;
}
#Override
public Map<String, String> unmarshal(MapWrapper v) throws Exception {
Map<String, String> map = new HashMap<String, String>();
if (v != null && v.elements != null && !v.elements.isEmpty()) {
for (Object object : v.elements) {
Element element = (Element) object;
map.put(element.getNodeName(), element.getNodeValue());
}
}
return map;
}
}
class MapWrapper {
#XmlAnyElement(lax=true)
protected List<JAXBElement<String>> elements;
}
And the below class can test the marshal and unmarshal of the above model:
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
public class TestEntry {
public static void main(String[] args) throws JAXBException {
testMarshal();
testUnmarshal();
}
public static void testMarshal() throws JAXBException {
Map<String, String> metadata = new HashMap<String, String>();
metadata.put("category", "test");
metadata.put("creation", new SimpleDateFormat("yyyy-MM-dd").format(new Date()));
TestModel model = new TestModel();
model.setMetadata(metadata);
model.setName("TESTMODEL");
marshal(model, System.out);
}
public static void testUnmarshal() throws JAXBException {
String model = "<?xml version='1.0' encoding='UTF-8' standalone='yes'?>"
+ "<TestModel>"
+ "<Name>TESTMODEL</Name>"
+ "<metadata>"
+ "<category>test</category>"
+ "<creation>2015-09-29</creation>"
+ "</metadata>"
+ "</TestModel>";
TestModel result = unmarshal(new ByteArrayInputStream(model.getBytes()), TestModel.class);
System.out.println("name=" + result.getName());
for (String key : result.getMetadata().keySet()) {
System.out.println(key + ", " + result.getMetadata().get(key));
}
}
public static <T> void marshal(T cls, OutputStream os) throws JAXBException {
JAXBContext context = JAXBContext.newInstance(cls.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(cls, os);
}
#SuppressWarnings("unchecked")
public static <T> T unmarshal(InputStream is, Class<T> cls)
throws JAXBException {
JAXBContext context = JAXBContext.newInstance(cls);
Unmarshaller unmarshaller = context.createUnmarshaller();
return (T) unmarshaller.unmarshal(is);
}
}
It seems that, the map only contains the key with 'null' value when invoke 'public Map unmarshal(MapWrapper v) throws Exception'.
And I also find a similar question about this issue "JAXB: how to marshall map into <key>value</key>", however, it didn't solve the unmarshal issue?

Answer 1

A very small correction:
map.put(element.getNodeName(), element.getTextContent());