Java JAXB Marshalling: How to avoid adding the XmlElement during the marshalling for elements with XMLAdapter

Question

I have a JSON file that I am converting to XML using the JAXB . I am reading the JSON using the Jackson then I am converting them to XML using the JAXB Marshalling process. The elements in JSON can be random user extension so I am using the @JsonAnyGetter to store it into MAP then I am using the adapter to convert them to XML elements.

I just wanted to know how can I skip the addition of the OuterElement or Parent element however I would like to retain the ÌnnerElement or Child element. Is there a or Child element. Is there a JAXB` way of doing it or else what can I do to achieve the following desired result?

Following is the JSON file:

{
  "google:g123": {
    "google:myField": "myValue"
  }
}

Following is the XML that I would like to obtain: (Expected)

<?xml version="1.0"?>
<extension>
    <google:g123>
        <google:myField>myValue</google:myField>
    </google:g123>
</extension>

Following is the XML that I am getting: (Current Behaviour) Observe the userextension tag which is being added automatically due to the variable name from the Extension.class . I would like to know how can I remove this tag but retain the inner elements.

<?xml version="1.0"?>
<extension>
    <userextension>
        <google:g123>
            <google:myField>myValue</google:myField>
        </google:g123>
    </userextension>
</extension>

Following is my Extension class to which JSON will be deserialized and based on which JAXB will marshal to create XML:

    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlRootElement(name = "extension")
    public class Extension {
        @XmlJavaTypeAdapter(ExtensionsAdapter.class)
        private Map < String, Object > userExtensions;

        @JsonAnyGetter
        public Map < String, Object > getUserExtensions() {
            return userExtensions;
        }

        @JsonAnySetter
        public void setUserExtensions(String key, Object value) {
            if (userExtensions == null) {
                userExtensions = new HashMap < String, Object > ();
            }
            userExtensions.put(key, value);
        }
    }

Following is my ExtensionAdapter.class :

public class ExtensionsAdapter extends XmlAdapter<ExtensionWrapper, Map<String, Object>> {

  private DocumentBuilder documentBuilder;

  public ExtensionsAdapter() throws Exception {
    documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
  }

  public static class ExtensionWrapper {
    @XmlAnyElement
    List elements;
  }

  @SuppressWarnings("unchecked")
  @Override
  public ExtensionWrapper marshal(Map<String, Object> extensions) throws Exception {
    if (extensions == null) {
      return null;
    }

    ExtensionWrapper wrapper = new ExtensionWrapper();
    List elements = new ArrayList();

    for (Map.Entry<String, Object> extension : extensions.entrySet()) {

      if (extension.getValue() instanceof Map) {
        elements.add(new JAXBElement<ExtensionWrapper>(new QName(getCleanLabel(extension.getKey())), ExtensionWrapper.class, marshal((Map) extension.getValue())));
      } else {
        elements.add(new JAXBElement<String>(new QName(getCleanLabel(extension.getKey())), String.class, extension.getValue().toString()));
      }
    }
    wrapper.elements = elements;
    return wrapper;
  }

  // Return a XML-safe attribute. Might want to add camel case support
  private String getCleanLabel(String attributeLabel) {
    attributeLabel = attributeLabel.replaceAll("[()]", "").replaceAll("[^\\w\\s]", "_").replaceAll(" ", "_");
    return attributeLabel;
  }

  @Override
  public Map<String, Object> unmarshal(ExtensionWrapper valurType) throws Exception {
    throw new NotImplementedException();
  }

}

I tried adding the @XmlAnyElement but thats resulting in the following error: ExtensionWrapper nor any of its super class is known to this context.

  @XmlJavaTypeAdapter(ExtensionsAdapter.class)
  @XmlAnyElement
  private Map<String, Object> userExtensions;

I just want to know how can I skip the addition of the userExtension tag during the marshalling. I just want to have all the inner elements.

Following is my main class:

public class Main
{
    public static void main(String[] args) {
        //jsonStream is the input json which I am reading from a file
        final JsonParser jsonParser = jsonFactory.createParser(jsonStream);
        jsonParser.setCodec(new ObjectMapper());
        final ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        final JsonNode jsonNode = jsonParser.readValueAsTree();
        final Extension eventInfo = objectMapper.treeToValue(jsonNode, Extension.class);
        JAXBContext context = JAXBContext.newInstance(Extension.class);
        Marshaller marshaller = context.createMarshaller(); 
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        marshaller.setProperty(Marshaller.JAXB_FRAGMENT, Boolean.TRUE);
        marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
        marshaller.marshal(((XmlSupportExtension) eventInfo).xmlSupport(), System.out);
    }
}

Answer 1

I was able to do it using the @XmlAnyElement(lax = true) . Posting the answer so it can be useful to somebody in the future who is looking for a similar answer and does not have to waste time trying to research.

I created an additional field:

 @XmlAccessorType(XmlAccessType.FIELD)
    @XmlRootElement(name = "extension")
    public class Extension {
        //Old field used only for getting value from JSON
        private Map < String, Object > userExtensions;
        //New Field which will be added to my XML
        @XmlElement(lax=true)
        private Object[] xmlExtensions;

        @JsonAnyGetter
        public Map < String, Object > getUserExtensions() {
            return userExtensions;
        }

        @JsonAnySetter
        public void setUserExtensions(String key, Object value) {
            if (userExtensions == null) {
                userExtensions = new HashMap < String, Object > ();
            }
            userExtensions.put(key, value);
        }
    }

I did not add this element to my propOder .

Then I used the a method to populate the fields from userExtension to XmlExtension :

private Object[] extensionBuilder(Map<String, Object> extensions) {
    if (extensions == null) {
      return null;
    }
    return extensions.entrySet().stream().map(extension -> {
      if (extension.getValue() instanceof Map) {

        // return new JAXBElement<JAXBElement>(new QName(getCleanLabel(extension.getKey())), JAXBElement.class,
        //    (JAXBElement) extensionBuilder((Map) extension.getValue())[0]);

        final Object[] result = extensionBuilder((Map) extension.getValue());
        return Arrays.stream(result)
            .map(innerExtension -> new JAXBElement<JAXBElement>(new QName(getCleanLabel(extension.getKey())), JAXBElement.class,
                (JAXBElement) innerExtension))
            .collect(Collectors.toList());
      } else {
        return Arrays
            .asList(new JAXBElement<String>(new QName(getCleanLabel(extension.getKey())), String.class, extension.getValue().toString()));
      }
    }).flatMap(List::stream).toArray(Object[]::new);
  }