Hi,
I recently encountered a problem where I pass one of my elements to the
insertBefore(a, b) method on Node and get a class cast exception. My design
uses composition to expose the Node Methods of an underlying Node, which in
this case it gets from Xerces. InsertBefore(Node a, Node b) should honor
its contract to accept anything implementing Node and do the job. However,
when I looked at the code for
https://svn.apache.org/repos/asf/xerces/java/trunk/src/org/apache/xerces/dom/ParentNode.javaI
see this in the internal implementation of the method:
// Convert to internal type, to avoid repeated casting
ChildNode newInternal = (ChildNode)newChild;
This cast makes the assumption that the implementation is
org.apache.xerces.dom.ChildNode. In my case it is not, but the underlying
element is. Therefore, I can get away with it by using
MyNode.getUndelyingNode, but I think that this is a bug as any
implementation should work. I would suggest that these classes could use
composition rather than casting to get an internal tye to use although I
don't know enough about the internal workings of xerces to make a
reccomendation. All I know is that casting an interface to an internal type
is probably going to cause problems for others too.
You could have ChildNode newInternel = new ChildNode(newChild); instead of
the above
public class ChildNode {
private Node node;
protected Node getNode() {
return this.node;
}
protected void setNode(Node node) {
this.node = node;
}
...
public Whatever someNodeMethod() {
return this.getNode().someNodeMethod();
}
...
}
I hope this is useful!
Regards,
Domenic Figliomeni
