com.icl.saxon.expr
Class SingletonExpression
java.lang.Object
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+--com.icl.saxon.expr.Expression
|
+--com.icl.saxon.expr.NodeSetExpression
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+--com.icl.saxon.expr.SingletonExpression
- Direct Known Subclasses:
- ContextNodeExpression, ParentNodeExpression, RootExpression
- public abstract class SingletonExpression
- extends NodeSetExpression
A node set expression that will always return zero or one nodes
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
SingletonExpression
public SingletonExpression()
getNode
public abstract NodeInfo getNode(Context context)
throws org.xml.sax.SAXException
- Get the single node to which this expression refers
selectFirst
public NodeInfo selectFirst(Context context)
throws org.xml.sax.SAXException
- Return the first node selected by this Expression when evaluated in the current context
- Overrides:
selectFirst
in class NodeSetExpression
- Parameters:
context
- The context for the evaluation- Returns:
- the NodeInfo of the first node in document order, or null if the node-set
is empty.
enumerate
public NodeEnumeration enumerate(Context context,
boolean sort)
throws org.xml.sax.SAXException
- Evaluate the expression in a given context to return a Node enumeration
- Overrides:
enumerate
in class NodeSetExpression
- Parameters:
context
- the evaluation contextsort
- Indicates result must be in document order
evaluateAsNodeSet
public NodeSetValue evaluateAsNodeSet(Context context)
throws org.xml.sax.SAXException
- Evaluate an expression as a NodeSet.
- Overrides:
evaluateAsNodeSet
in class NodeSetExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the value of the expression, evaluated in the current context
evaluateAsString
public java.lang.String evaluateAsString(Context context)
throws org.xml.sax.SAXException
- Evaluate as a string. Returns the string value of the node if it exists
- Overrides:
evaluateAsString
in class NodeSetExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- true if there are any nodes selected by the NodeSetExpression
evaluateAsBoolean
public boolean evaluateAsBoolean(Context context)
throws org.xml.sax.SAXException
- Evaluate as a boolean. Returns true if there are any nodes
selected by the NodeSetExpression
- Overrides:
evaluateAsBoolean
in class NodeSetExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- true if there are any nodes selected by the NodeSetExpression