Class Pattern

java.lang.Object
net.sf.saxon.pattern.Pattern
All Implemented Interfaces:
Serializable, SourceLocator, Container, PatternFinder
Direct Known Subclasses:
AnchorPattern, ConditionalPattern, ItemTypePattern, LocationPathPattern, NodeSetPattern, PatternWithPredicate, VennPattern
public abstract class Pattern extends Object implements PatternFinder, Serializable, Container
A Pattern represents the result of parsing an XSLT pattern string.
Patterns are created by calling the static method Pattern.make(string).
The pattern is used to test a particular node by calling match().
See Also:

  • Constructor Details

    • Pattern

      public Pattern()

  • Method Details

    • make

      public static Pattern make(String pattern, StaticContext env, Executable exec) throws XPathException
      Static factory method to make a Pattern by parsing a String.
      Parameters:
      pattern - The pattern text as a String
      env - An object defining the compile-time context for the expression
      exec - The executable containing this pattern
      Returns:
      The pattern object
      Throws:
      XPathException - if the pattern is invalid

    • getExecutable

      public Executable getExecutable()
      Get the executable containing this pattern
      Specified by:
      getExecutable in interface Container
      Returns:
      the executable

    • setExecutable

      public void setExecutable(Executable executable)
      Set the executable containing this pattern
      Parameters:
      executable - the executable

    • getLocationProvider

      public LocationProvider getLocationProvider()
      Get the LocationProvider allowing location identifiers to be resolved.
      Specified by:
      getLocationProvider in interface Container
      Returns:
      the location provider

    • getContainerGranularity

      public int getContainerGranularity()
      Get the granularity of the container.
      Specified by:
      getContainerGranularity in interface Container
      Returns:
      0 for a temporary container created during parsing; 1 for a container that operates at the level of an XPath expression; 2 for a container at the level of a global function or template

    • setOriginalText

      public void setOriginalText(String text)
      Set the original text of the pattern for use in diagnostics
      Parameters:
      text - the original text of the pattern

    • setVariableBindingExpression

      public void setVariableBindingExpression(Expression exp)
      Set an expression used to bind the variable that represents the value of the current() function
      Parameters:
      exp - the expression that binds the variable

    • simplify

      public Pattern simplify(ExpressionVisitor visitor) throws XPathException
      Simplify the pattern by applying any context-independent optimisations. Default implementation does nothing.
      Parameters:
      visitor - the expression visitor
      Returns:
      the optimised Pattern
      Throws:
      XPathException - if a static error is discovered

    • analyze

      public Pattern analyze(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Type-check the pattern.
      Parameters:
      visitor - the expression visitor
      contextItemType - the type of the context item at the point where the pattern is defined. Set to null if it is known that the context item is undefined.
      Returns:
      the optimised Pattern
      Throws:
      XPathException - if a static error is discovered

    • 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.
      Returns:
      the dependencies, as a bit-significant mask

    • iterateSubExpressions

      public Iterator iterateSubExpressions()
      Iterate over the subexpressions within this pattern
      Returns:
      an iterator over the subexpressions. Default implementation returns an empty sequence

    • allocateSlots

      public int allocateSlots(StaticContext env, SlotManager slotManager, int nextFree)
      Allocate slots to any variables used within the pattern
      Parameters:
      env - the static context in the XSLT stylesheet
      slotManager - the slot manager representing the stack frame for local variables
      nextFree - the next slot that is free to be allocated
      Returns:
      the next slot that is free to be allocated

    • resolveCurrent

      public void resolveCurrent(LetExpression let, PromotionOffer offer, boolean topLevel) throws XPathException
      If the pattern contains any calls on current(), this method is called to modify such calls to become variable references to a variable declared in a specially-allocated local variable
      Parameters:
      let - the expression that assigns the local variable. This returns a dummy result, and is executed just before evaluating the pattern, to get the value of the context item into the variable.
      offer - A PromotionOffer used to process the expressions and change the call on current() into a variable reference
      topLevel - true if this is an external call rather than an internal recursive call
      Throws:
      XPathException - if an error occurs

    • promote

      public void promote(PromotionOffer offer, Expression parent) 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.

      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
      parent - the expression acting as parent of this pattern
      Throws:
      XPathException - if any error is detected

    • setSystemId

      public void setSystemId(String systemId)
      Set the system ID where the pattern occurred
      Parameters:
      systemId - the URI of the module containing the pattern

    • setLineNumber

      public void setLineNumber(int lineNumber)
      Set the line number where the pattern occurred
      Parameters:
      lineNumber - the line number of the pattern in the source module

    • matches

      public abstract boolean matches(Item item, XPathContext context) throws XPathException
      Determine whether this Pattern matches the given item. This is the main external interface for matching patterns: it sets current() to the node being tested
      Parameters:
      item - 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 - if a dynamic error occurs during pattern matching

    • matchesBeneathAnchor

      public boolean matchesBeneathAnchor(NodeInfo node, NodeInfo anchor, XPathContext context) throws XPathException
      Determine whether this pattern matches a given Node within the subtree rooted at a given anchor node. This method is used when the pattern is used for streaming.
      Parameters:
      node - The NodeInfo representing the Element or other node to be tested against the Pattern
      anchor - The anchor node, which must match any AnchorPattern subpattern
      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 - if a dynamic error occurs during pattern matching

    • internalMatches

      protected boolean internalMatches(NodeInfo node, NodeInfo anchor, XPathContext context) throws XPathException
      Determine whether this Pattern matches the given Node. This is an internal interface used for matching sub-patterns; it does not alter the value of current(). The default implementation is identical to matches().
      Parameters:
      node - The NodeInfo representing the Element or other node to be tested against the Pattern
      anchor - The anchor node, which must match any AnchorPattern subpattern
      context - The dynamic context. Only relevant if the pattern uses variables, or contains calls on functions such as document() or key(). @return true if the node matches the Pattern, false otherwise
      Returns:
      true if the pattern matches the supplied node
      Throws:
      XPathException - if a dynamic error occurs during pattern matching

    • selectNodes

      public SequenceIterator<? extends NodeInfo> selectNodes(DocumentInfo doc, XPathContext context) throws XPathException
      Select nodes in a document using this PatternFinder.
      Specified by:
      selectNodes in interface PatternFinder
      Parameters:
      doc - the document node at the root of a tree
      context - the dynamic evaluation context
      Returns:
      an iterator over the selected nodes in the document.
      Throws:
      XPathException

    • getNodeKind

      public int getNodeKind()
      Determine the types of nodes to which this pattern applies. Used for optimisation. For patterns that match nodes of several types, return Type.NODE. For patterns that do not match nodes, return -1.
      Returns:
      the type of node matched by this pattern. e.g. Type.ELEMENT or Type.TEXT

    • getFingerprint

      public int getFingerprint()
      Determine the name fingerprint of nodes to which this pattern applies. Used for optimisation.
      Returns:
      A fingerprint that the nodes must match, or -1 if it can match multiple fingerprints, or it if matches atomic values

    • getItemType

      public abstract ItemType getItemType()
      Get an ItemType that all the items matching this pattern must satisfy
      Returns:
      an ItemType, as specific as possible, which all the matching items satisfy

    • getDefaultPriority

      public double getDefaultPriority()
      Determine the default priority to use if this pattern appears as a match pattern for a template with no explicit priority attribute.
      Returns:
      the default priority for the pattern

    • getSystemId

      public String getSystemId()
      Get the system id of the entity in which the pattern occurred
      Specified by:
      getSystemId in interface SourceLocator

    • getLineNumber

      public int getLineNumber()
      Get the line number on which the pattern was defined
      Specified by:
      getLineNumber in interface SourceLocator

    • getColumnNumber

      public int getColumnNumber()
      Get the column number (always -1)
      Specified by:
      getColumnNumber in interface SourceLocator

    • getPublicId

      public String getPublicId()
      Get the public ID (always null)
      Specified by:
      getPublicId in interface SourceLocator

    • toString

      public String toString()
      Get the original pattern text
      Overrides:
      toString in class Object

    • getHostLanguage

      public int getHostLanguage()
      Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
      Specified by:
      getHostLanguage in interface Container
      Returns:
      typically Configuration.XSLT or Configuration.XQUERY

    • replaceSubExpression

      public boolean replaceSubExpression(Expression original, Expression replacement)
      Replace a subexpression by a replacement subexpression
      Parameters:
      original - the expression to be replaced
      replacement - the new expression to be inserted in its place
      Returns:
      true if the replacement was carried out