UpdateAgent

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface UpdateAgent
```
An UpdateAgent is a callback class that is called to handle a document after it has been updated. Typically the UpdateAgent might take responsibility for writing the updated document back to persistent storage.

- Method Summary
  
  All Methods Instance Methods Abstract Methods
  Modifier and Type Method Description
  
  void update(NodeInfo node, Controller controller)
  Handle an updated document.

- Method Detail
  - update
```
void update(NodeInfo node,
            Controller controller)
     throws XPathException
```
    Handle an updated document. This method is called by XQueryExpression.runUpdate(DynamicQueryContext, UpdateAgent) once for each document (or more generally, for the root of each tree) that has been modified by the update query.
    
    Parameters:
    
    node - the root of the tree that has been updated
    
    controller - the Controller that was used for executing the query
    
    Throws:
    
    XPathException - if the callback code cannot handle the updated document