net.sf.saxon.pattern
Class KeyPattern

java.lang.Object
  extended by net.sf.saxon.pattern.Pattern
      extended by net.sf.saxon.pattern.KeyPattern
All Implemented Interfaces:
Serializable, SourceLocator, Container, PatternFinder

public final class KeyPattern
extends Pattern

A KeyPattern is a pattern of the form key(keyname, keyvalue)

See Also:
Serialized Form

Constructor Summary
KeyPattern(StructuredQName keyName, Expression key)
          Constructor
 
Method Summary
 Pattern analyze(ExpressionVisitor visitor, ItemType contextItemType)
          Type-check the pattern.
 int getDependencies()
          Get the dependencies of the pattern.
 NodeTest getNodeTest()
          Get a NodeTest that all the nodes matching this pattern must satisfy
 Iterator iterateSubExpressions()
          Iterate over the subexpressions within this pattern
 boolean matches(NodeInfo e, XPathContext context)
          Determine whether this Pattern matches the given Node.
 void promote(PromotionOffer offer)
          Offer promotion for subexpressions within this pattern.
 
Methods inherited from class net.sf.saxon.pattern.Pattern
getColumnNumber, getDefaultPriority, getExecutable, getFingerprint, getHostLanguage, getLineNumber, getLocationProvider, getNodeKind, getPublicId, getSystemId, make, makeSearchExpression, replaceSubExpression, selectNodes, setExecutable, setLineNumber, setOriginalText, setSystemId, simplify, toString
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

KeyPattern

public KeyPattern(StructuredQName keyName,
                  Expression key)
Constructor

Parameters:
keyName - the name of the key
key - the value of the key: either a StringValue or a VariableReference
Method Detail

analyze

public Pattern analyze(ExpressionVisitor visitor,
                       ItemType contextItemType)
                throws XPathException
Type-check the pattern. This is needed for patterns that contain variable references or function calls.

Overrides:
analyze in class Pattern
Parameters:
visitor - the expression visitor
contextItemType - the type of the context item, if known, at the point where the pattern is defined
Returns:
the optimised Pattern
Throws:
XPathException

getDependencies

public int getDependencies()
Get the dependencies of the pattern. The only possible dependency for a pattern is on local variables. This is analyzed in those patterns where local variables may appear.

Overrides:
getDependencies in class Pattern
Returns:
the dependencies, as a bit-significant mask

iterateSubExpressions

public Iterator iterateSubExpressions()
Iterate over the subexpressions within this pattern

Overrides:
iterateSubExpressions in class Pattern
Returns:
an iterator over the subexpressions. Default implementation returns an empty sequence

promote

public void promote(PromotionOffer offer)
             throws XPathException
Offer promotion for subexpressions within this pattern. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

Unlike the corresponding method on Expression, this method does not return anything: it can make internal changes to the pattern, but cannot return a different pattern. Only certain kinds of promotion are applicable within a pattern: specifically, promotions affecting local variable references within the pattern.

Overrides:
promote in class Pattern
Parameters:
offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
Throws:
XPathException - if any error is detected

matches

public boolean matches(NodeInfo e,
                       XPathContext context)
                throws XPathException
Determine whether this Pattern matches the given Node.

Specified by:
matches in class Pattern
Parameters:
e - The NodeInfo representing the Element or other node to be tested against the Pattern
context - The dynamic context. Only relevant if the pattern uses variables, or contains calls on functions such as document() or key().
Returns:
true if the node matches the Pattern, false otherwise
Throws:
XPathException

getNodeTest

public NodeTest getNodeTest()
Get a NodeTest that all the nodes matching this pattern must satisfy

Specified by:
getNodeTest in class Pattern
Returns:
a NodeTest, as specific as possible, which all the matching nodes satisfy


Copyright (C) Michael H. Kay. All rights reserved.