XmlAdapter和JSON的MOXy异常

Question

I'm running MOXy 2.5.0 and getting a ClassCastException with an XmlAdapter , but only when trying to output JSON; the XML output works fine.

I've got a wrapper class that looks like this:

@XmlAccessorType(XmlAccessType.NONE)
public abstract class ListWrapper<T> implements List<T>
{
    private List<T> list = new ArrayList<T>();

    @XmlElement
    private Foo foo;  // stuff specific to my problem domain

    public ListWrapper()
    {
    }

    public ListWrapper(Foo foo, List list)
    {
        this.foo = foo;
        this.list = list;
    }

    // ... implementation of List<T> using the list member ...
}

There are descendants of this class that look like this:

@XmlRootElement(name = "recordList")
@XmlAccessorType(XmlAccessType.NONE)
public class RecordList extends ListWrapper<Record>
{
    public RecordList()
    {
        super();
    }

    public RecordList(Foo foo, List<Record> list)
    {
        super(foo, list);
    }

    @Override
    @XmlElementWrapper(name = "records")
    @XmlElement(name = "record", type = Record.class)
    public List<Record> getList()
    {
        return super.getList();
    }
}

There is then an XmlAdapter for RecordList that looks like this:

public class RecordListAdapter extends XmlAdapter<RecordList, RecordList>
{
    @Override
    public RecordList unmarshal(RecordList v) throws Exception
    {
        return v;
    }

    @Override
    public RecordList marshal(RecordList v) throws Exception
    {
        return v;
    }
}

Finally there is a class that contains members like RecordList and declares them as such:

@XmlRootElement(name = "container")
@XmlAccessorType(XmlAccessType.NONE)
public class Container
{
    @XmlElement
    @XmlJavaTypeAdapter(RecordListAdapter.class)
    protected RecordList recordList;

    // ... other stuff ...
}

With the reference JAXB implementation this works fine in both XML and JSON (we were using Jackson for the JSON logic). With a change to MOXy (and removal of Jackson) I'll get an exception trace similar to the following when asking for JSON output.

javax.xml.bind.MarshalException - with linked exception:[Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-3001] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ConversionException
Exception Description: The object [1], of class [class com.example.Record], could not be converted to [class com.example.RecordList].
Internal Exception: java.lang.ClassCastException: com.example.Record cannot be cast to com.example.RecordList]
    at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:403)
...
Caused by: Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-3001] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ConversionException
Exception Description: The object [1], of class [class com.example.Record], could not be converted to [class com.example.RecordList].
Internal Exception: java.lang.ClassCastException: com.example.Record cannot be cast to com.example.RecordList
    at org.eclipse.persistence.exceptions.XMLMarshalException.marshalException(XMLMarshalException.java:97)
...
Caused by: Exception [EclipseLink-3001] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.ConversionException
Exception Description: The object [1], of class [class com.example.Record], could not be converted to [class com.example.RecordList].
Internal Exception: java.lang.ClassCastException: com.example.Record cannot be cast to com.example.RecordList
    at org.eclipse.persistence.exceptions.ConversionException.couldNotBeConverted(ConversionException.java:87)
...
Caused by: java.lang.ClassCastException: com.example.Record cannot be cast to com.example.RecordList
    at com.example.RecordListAdapter.marshal(RecordListAdapter.java:5)
    at org.eclipse.persistence.internal.jaxb.XMLJavaTypeConverter.convertObjectValueToDataValue(XMLJavaTypeConverter.java:172)

I'm not sure why MOXy is trying to tread a Record as a RecordList , but it appears as though that's what is happening. Like I said, this does not happen with the reference (ie Sun) implementation of JAXB; it only happens when I'm trying to use MOXy.

Any ideas here? Thanks.

Answer 1

After you removed Jackson you no longer have a write adapter for JSON. You need to tell the server how it should produce JSON.

Answer 2

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

One difference between MOXy and the other technologies that you are using is that MOXy will treat RecordList and ListWrapper as a java.util.List as it implements java.util.List . As such a XmlAdapter can not be applied to it, as it can only apply to items in the collection.