XmlAdapter和JSON的MOXy异常

Question

我运行的是JSON2.5.0，并获得了一个带有XmlAdapter的ClassCastException，但只有在尝试输出XmlAdapter时才能正常工作。

我有一个包装类，看起来像这样：

@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 ...
}

该类的子类如下所示：

@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();
    }
}

然后有一个用于RecordList的XmlAdapter，如下所示：

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;
    }
}

最后还有一个类，它包含像RecordList这样的成员，并这样声明它们：

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

    // ... other stuff ...
}

使用参考JAXB实现，这在XML和JSON中都可以很好地工作(我们将Jackson用于JSON逻辑)。通过更改MOXy (并删除JSON )，在请求JSON输出时，我将得到类似以下内容的异常跟踪。

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)

我不确定为什么MOXy要把Record当做RecordList来对待，但看起来这就是事实。正如我所说的，这种情况不会发生在JAXB的引用(即Sun)实现中；只有当我尝试使用MOXy时才会发生这种情况。

这里有什么想法吗？谢谢。

Answer 1

删除Jackson之后，您将不再拥有用于JSON的写入适配器。您需要告诉服务器应该如何生成JSON。

Answer 2

注意：我是的负责人，也是专家组的成员。

MOXy与您正在使用的其他技术之间的一个不同之处在于，MOXy将RecordList和ListWrapper视为java.util.List，因为它实现了java.util.List。这样的XmlAdapter不能应用于它，因为它只能应用于集合中的项。