: Class NodeSetExpression
com.icl.saxon.expr
Class NodeSetExpression
java.lang.Object
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+--com.icl.saxon.expr.Expression
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+--com.icl.saxon.expr.NodeSetExpression
Direct Known Subclasses: NodeListExpression , PathExpression , SingletonExpression , SortedSelection
public abstract class NodeSetExpression extends Expression
A NodeSetExpression is any expression denoting a set of nodes.
This is an abstract class, the methods are defaults which may be overridden in subclasses
Methods inherited from class com.icl.saxon.expr.Expression
containsReferences , display , evaluateAsNumber , getDependencies , getStaticContext , indent , isContextDocumentNodeSet , make , reduce , setStaticContext , simplify , usesCurrent
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
NodeSetExpression
public NodeSetExpression ()
enumerate
public abstract NodeEnumeration enumerate (Context context,
boolean sorted)
throws XPathException
Return a node enumeration. All NodeSetExpressions must implement this method:
the evaluate() function is defined in terms of it. (But note that some expressions
that return node-sets are not NodeSetExpressions: for example functions such as
key(), id(), and document() are not, and neither are variable references).
Overrides: enumerate
in class Expression
Parameters: context
- The evaluation contextsorted
- True if the nodes must be returned in document order
evaluate
public Value evaluate (Context context)
throws XPathException
Evaluate this node-set. This doesn't actually retrieve all the nodes: it returns a wrapper
around a node-set expression in which all context dependencies have been eliminated.
Overrides: evaluate
in class Expression
Following copied from class: com.icl.saxon.expr.Expression
Parameters: context
- The context in which the expression is to be evaluatedReturns: the value of the expression, evaluated in the current context
selectFirst
public NodeInfo selectFirst (Context context)
throws XPathException
Return the first node selected by this Expression when evaluated
in the current context
Parameters: context
- The context for the evaluationReturns: the NodeInfo of the first node in document order, or null if the node-set
is empty.
evaluateAsString
public java.lang.String evaluateAsString (Context context)
throws XPathException
Evaluate as a string. Returns the string value of the first node
selected by the NodeSetExpression
Overrides: evaluateAsString
in class Expression
Parameters: context
- The context in which the expression is to be evaluatedReturns: the value of the NodeSetExpression, evaluated in the current context
outputStringValue
public void outputStringValue (Outputter out,
Context context)
throws javax.xml.transform.TransformerException
Evaluate an expression as a String and write the result to the
specified outputter.
Overrides: outputStringValue
in class Expression
Parameters: context
- The context in which the expression is to be evaluatedReturns: the value of the expression, evaluated in the current context
evaluateAsBoolean
public boolean evaluateAsBoolean (Context context)
throws XPathException
Evaluate as a boolean. Returns true if there are any nodes
selected by the NodeSetExpression
Overrides: evaluateAsBoolean
in class Expression
Parameters: context
- The context in which the expression is to be evaluatedReturns: true if there are any nodes selected by the NodeSetExpression
evaluateAsNodeSet
public NodeSetValue evaluateAsNodeSet (Context context)
throws XPathException
Evaluate an expression as a NodeSet.
Overrides: evaluateAsNodeSet
in class Expression
Parameters: context
- The context in which the expression is to be evaluatedReturns: the value of the expression, evaluated in the current context
getDataType
public int getDataType ()
Determine the data type of the exprssion, if possible
Overrides: getDataType
in class Expression
Returns: Value.NODESET