在不更改架构的情况下更改类

Question

I have a xsd schema which I'm not allowed to change. It produce generated java classes.

Assume that classes looks as follows:

       class Data {
          protected List<Value> value;
          ... 
       }
       class Value {
           ...
        }

Now I need to have my own MyValue ideally to be extended from Value.

class MyValue extends Value {

     Integer myOwnField1;
     Long anotherProperty;

}

And be able to say unmarshaller to use MyValue instead of Value when it parses xml file.

Later I would be able to use the fact that MyValue can contain some useful new fields inside, make operations over them, change them, etc. So I want extend the functionality which I have in schema without changing it.

Is that somehow possible to replace Value by MyValue for unmarshaller?

Apart from the obvious way to create a Map where I can map object which was generated by unmarshaller with my own fields and properties in MyValue. I'd like to avoid this way.

Answer 1

Can you load the list using bean properties?

public void setValue(List<Value> value) {
    this.value = ...convert to List<MyValue>...
}

Answer 2

You might be interested in unmarshalling by declared type : indeed, if you override your XSD from the root element to every child element you need to override, you could use a second argument in unmarshal method to sepecify your custom mapping.

<T> JAXBElement<T> unmarshal(Source source,
                             Class<T> declaredType)
                         throws JAXBException

[...] declaredType - appropriate JAXB mapped class to hold source's xml root element

(see Unmarshaller javadoc for more detailed info)