@XmlPath(".") conflicts with @XmlAdapter

Question

having this Jaxb Xml definition, i try to remove the Map Elements Wrapper by adding @XmlPath(".") but it cause exception during the unmarchaling

@XmlRootElement
public abstract class ViewElement{
    @XmlJavaTypeAdapter(value=EventAdapter.class)   
    public Map<Event, String> getEvents() {     
    }
    private transient Class entityType;
    public Class getEntityType() {
        return entityType;
    }
}

And the EventAdapter is

public class EventAdapter extends XmlAdapter<EventAdapter.AdaptedMap, Map<Event, String>> { 
    public static class AdaptedMap {
        @XmlVariableNode("key")
        List<AdaptedEntry> entries = new ArrayList<AdaptedEntry>();
    }
    public static class AdaptedEntry {
        @XmlTransient
        public String key;
        @XmlValue
        public String value;
    }
    .....       
}

my output was

<element>
   <events>
      <onCellEdit>do some thing<onCellEdit>
   </events>
   <entityType>com.agitech.erp.model.erp.ErpFolder</entityType>
<element>

I try to remove the <events> tag by adding @XmlPath(".")

@XmlPath(".")
@XmlJavaTypeAdapter(value=EventAdapter.class)   
public Map<Event, String> getEvents() {     
}

The output is good

<element>
   <onCellEdit>do some thing<onCellEdit>       
   <entityType>com.agitech.erp.model.erp.ErpFolder</entityType>
<element>

but the unmarchaling faileds

Caused by: Exception [EclipseLink-3002] (Eclipse Persistence Services - 2.6.0.v20140809-296a69f): org.eclipse.persistence.exceptions.ConversionException
Exception Description: The object [], of class [class java.lang.String], from mapping [org.eclipse.persistence.oxm.mappings.XMLDirectMapping[entityType-->view.entityType/text()]] with descriptor [XMLDescriptor(com.agitech.erp.view.BeanView --> [DatabaseTable(view), DatabaseTable(viewFrame), DatabaseTable(viewElement)])], could not be converted to [class java.lang.Class].
Internal Exception: java.lang.ClassNotFoundException: 
    at org.eclipse.persistence.exceptions.ConversionException.couldNotBeConvertedToClass(ConversionException.java:95)
    at org.eclipse.persistence.internal.helper.ConversionManager.convertObjectToClass(ConversionManager.java:446)

Debuging Jaxb bring me to the line

org.eclipse.persistence.internal.oxm.XMLDirectMappingNodeValue

public void endElement(XPathFragment xPathFragment, UnmarshalRecord unmarshalRecord) {
    ...
    line 205 unmarshalRecord.setAttributeValue(convertedValue, xmlDirectMapping);
}

During the unmarchaling of entityType value, the UnmarshalRecordImpl.currentObj contains the EventAdapter instead of the parent element

I modify org.eclipse.persistence.internal.oxm.record.UnmarshalRecordImpl

public XPathNode getNonAttributeXPathNode(String namespaceURI, String localName, String qName, Attributes attributes) {
....
    if(null == resultNode && null == nonPredicateNode) {
        // ANY MAPPING
        resultNode = xPathNode.getAnyNode();
// by default it return the EventAdapter, changing it to NULL fix my problem
    }
....
}

Not a safe solution

Answer 1

I have been able to reproduce the issue that you are seeing, but haven't yet worked out the cause. You can use the following bug to track the progress on this issue:

• http://bugs.eclipse.org/457169

Answer 2

After trying a lot of things, I was able to find a workaround for this issue. I thought of posting here the same so it can be helpful to someone else in the future. The lead has confirmed the issue around 5 years ago but seems like they have not fixed it and I was facing a similar issue.

Basically, we can use the beforeMarshal and afterUnmarshal methods to change the values in the fields.

1. You need to create a field List<Object> with @XmlAnyElement(lax=true) along with Map<String,Object>.
2. Remove the @XmlPath(".") and the XMLAdapter class.
3. Mark the field Map<String, Object> with @XmlTransient.

Now within the beforeMarshal and afterMarshal fields, you can exchange the data. During the unmarshal in beforeunmarshal, all the unknown field values will be present within the List<Object> loop over it and add it to the Map<String, Object>.

Similarly during the marshaling, you can move the values Map<String, Object> to List<Object> by creating the DOM elements.

Marshaling all values are added to root as DOM Elements are present and during Unmarshaling known values are read first and then-unknown values are stored within List<Object> due to @XmlAnyElement.

I have created an example using the Customer class, you can modify it accordingly for your need.

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, visible = true, property = "isA")
@JsonInclude(Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
@XmlRootElement(name = "Customer")
@XmlType(name = "Customer", propOrder = {"name", "age", "otherElements"})
@XmlAccessorType(XmlAccessType.FIELD)
@Getter
@Setter
@AllArgsConstructor
@ToString
@NoArgsConstructor
public class Customer {
    @XmlTransient
    private String isA;
    private String name;
    private String age;

    @XmlAnyElement(lax = true)
    @JsonIgnore
    private List<Object> otherElements = new ArrayList<>();


    @JsonIgnore
    @XmlTransient
    private Map<String, Object> userExtensions = new HashMap<>();

    @JsonAnyGetter
    @JsonSerialize(using = CustomExtensionsSerializer.class)
    public Map<String, Object> getUserExtensions() {
        return userExtensions;
    }

    @JsonAnySetter
    public void setUserExtensions(String key, Object value) {
        userExtensions.put(key, value);
    }

    private void beforeMarshal(Marshaller m) throws ParserConfigurationException {
        System.out.println("Before Marshalling User Extension: " + userExtensions);
        ExtensionsModifier extensionsModifier = new ExtensionsModifier();
        otherElements = extensionsModifier.Marshalling(userExtensions);
        System.out.println("Before Marshalling Final Other Elements " + otherElements);
        userExtensions = new HashMap<>();
    }

    private void afterUnmarshal(Unmarshaller m, Object parent) throws ParserConfigurationException {
        System.out.println("After Unmarshalling : " + otherElements);
        ExtensionsModifier extensionsModifier = new ExtensionsModifier();
        userExtensions = extensionsModifier.Unmarshalling(otherElements);
        otherElements = new ArrayList();
    }
}

You can refer the creation of DOM ELEMENTS here:https://stackoverflow.com/a/24239105/7584240

You can refer my complete answer here: https://stackoverflow.com/a/67923216/7584240