Class AdaptiveResultTreeImpl

AdaptiveResultTreeImpl is a adaptive DOM model for result tree fragments (RTF). It is used in the case where the RTF is likely to be pure text yet it can still be a DOM tree. It is designed for RTFs which have <xsl:call-template> or <xsl:apply-templates> in the contents. Example:

    <xsl:variable name = "x">
      <xsl:call-template name = "test">
         <xsl:with-param name="a" select="."/>
      </xsl:call-template>
    </xsl:variable>
 

In this example the result produced by is likely to be a single Text node. But it can also be a DOM tree. This kind of RTF cannot be modelled by SimpleResultTreeImpl.

AdaptiveResultTreeImpl can be considered as a smart switcher between SimpleResultTreeImpl and SAXImpl. It treats the RTF as simple Text and uses the SimpleResultTreeImpl model at the beginning. However, if it receives a call which indicates that this is a DOM tree (e.g. startElement), it will automatically transform itself into a wrapper around a SAXImpl. In this way we can have a light-weight model when the result only contains simple text, while at the same time it still works when the RTF is a DOM tree.

All methods in this class are overridden to delegate the action to the wrapped SAXImpl object if it is non-null, or delegate the action to the SimpleResultTreeImpl if there is no wrapped SAXImpl.

%REVISIT% Can we combine this class with SimpleResultTreeImpl? I think it is possible, but it will make SimpleResultTreeImpl more expensive. I will use two separate classes at this time.