JAXB Eclipse MOXy Nullable value and retrieve only a specified key in a Map

Question

I have another more tricky question:

E.g. Person Class has: --String firstName --String lastName --Map stringMap

   Person person = new Person ();
   person.setFirstName("FirstName");
   person.setLastName("LastName");
   Map<String,String> stringMap = new HashMap<String,String>();
   stringMap.put("IwantThisKeyInXml","IwantThisValueInXml");
   stringMap.put("IDONTwantThisKeyInXml","IDONTwantThisValueInXml");


   InputStream iStream1 = classLoader.getResourceAsStream("person-binding.xml");
   List<Object> fileList = new ArrayList<Object>();
            fileList.add(iStream1);
   Map<String, Object> properties = new HashMap<String,Object>();               

   properties.put(JAXBContextProperties.OXM_METADATA_SOURCE,  fileList);
   JAXBContext ctx = JAXBContext.newInstance(new Class[] { GaDictionary.class, Person.class }, properties);

   Marshaller marshaller = ctx.createMarshaller();
   marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

   Writer output = new StringWriter();
   marshaller.marshal(person, output);
   System.out.println(output);

person-binding.xml is below

   <?xml version="1.0"?>
   <xml-bindings
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="my.test.model"  xml-mapping-metadata-complete="true">
    <xml-schema
        element-form-default="QUALIFIED"/>
    <java-types>
        <java-type name="Person"  xml-accessor-type="NONE">
            <xml-root-element/>
            <xml-type prop-order="firstName lastName"/>
            <java-attributes>
                <xml-element java-attribute="firstName" name="first-name"/>
                <xml-element java-attribute="lastName" name="last-name"/>
                <xml-element java-attribute="stringMap" name="string-map"/>
            </java-attributes>
        </java-type>
      </java-types>
    </xml-bindings>

So accordingly the definition the result is:

   <?xml version="1.0" encoding="UTF-8"?>
   <person>
   <first-name>FirstName</first-name>
   <last-name>LastName</last-name>
   <string-map>
      <entry>
         <key>IwantThisKeyInXml</key>
         <value>IwantThisKeyInXml</value>
      </entry>
      <entry>
         <key>IDONTwantThisKeyInXml</key>
         <value>IDONTwantThisKeyInXml</value>
      </entry>
   </string-map>
   </person>

How Could I exclude that entry on the stringMap? I tried with virtual access method but maybe I wasn't able to configure it properly?! Should I remove that value after marshaling? Which could it be a smart and maintainable way?

Last question is if I have null value for a property. How could I configure the person-binding-xml file (oxm.file) to get the relative xml tag empty?

I could change the model class but I prefer don't add any lines of code if it's possible. (This is the reason why I populated the xml file)

So the result that I would like to obtain is:

 <?xml version="1.0" encoding="UTF-8"?>
   <person>
     <first-name>FirstName</first-name>
     <last-name>LastName</last-name>
     <string-map>
       <entry>
         <key>IwantThisKeyInXml</key>
         <value>IwantThisKeyInXml</value>
       </entry>
      </string-map>
  </person>

For the second related question: I tried nillable="true" in but it doesn't work ! So For istance If I have a null value for a stringMap or firstName or something else I will get respectively and tag closed with any body.

Or another way that I would like to obtain is:

 <?xml version="1.0" encoding="UTF-8"?>
   <person>
     <first-name>FirstName</first-name>
     <last-name>LastName</last-name>
     <string-map>
       <entry>
         <key>IwantThisKeyInXml</key>
         <value>IwantThisKeyInXml</value>
       </entry>
       <entry><!-- I have the entry but I have an empty value-->
         <key>KEY</key>
         <value></value>
       </entry>
      </string-map>
  </person>

Thanks to all

Answer 1

I found the right solution:

        import java.util.HashMap;
        import java.util.Map;
        import java.util.Map.Entry;

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

        public final class StringMapAdapter extends XmlAdapter<StringAdapterMap, Map<String, String>> {

            private final String OMIT = "birthPlaceString";

            @Override
            public Map<String, String> unmarshal(StringAdapterMap v) throws Exception {
                 HashMap<String, String> hashMap = new HashMap<String, String>();
                 System.out.println("unmarshal"); 
                 for(StringEntryType myEntryType : v.entry) {
                     hashMap.put(myEntryType.key, myEntryType.value);
                  }
                  return hashMap;
            }

            @Override
            public StringAdapterMap marshal(Map<String, String> v) throws Exception {
                StringAdapterMap myMapType = new StringAdapterMap();
              for(Entry<String, String> entry : v.entrySet()) {
                  StringEntryType EntryType = new StringEntryType();
                   EntryType.key= entry.getKey();
                   EntryType.value = entry.getValue();
                   if (!OMIT.equals(EntryType.key))
                       myMapType.entry.add(EntryType);
              }
              return myMapType;

            }

StringAdapterMap class:

        import java.util.ArrayList;
        import java.util.List;

        public class StringAdapterMap {
             public List<StringEntryType> entry = new ArrayList<StringEntryType>();

        }

StringEntryType class:

        public class StringEntryType {

               public String key;

               public String value;

        }

in oxm.file remember to configure the adapter

     <xml-element java-attribute="stringMap" name="string-map" >
      <xml-java-type-adapter value="it.cineca.jaxb.adapter.StringMapAdapter" />    
     </xml-element>