Package net.sf.saxon.expr

Class AttributeGetter

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.AttributeGetter
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
public final class AttributeGetter extends Expression
An AttributeGetter is an expression that returns the value of a specific attribute of the context item, provided that it is an untyped element node. That is, it represents the expression data(./@name) assuming that all data is untyped.

  • Constructor Details

  • Method Details

    • getAttributeName

      public FingerprintedQName getAttributeName()

    • getItemType

      public ItemType getItemType()
      Description copied from class: Expression
      Determine the static item type of the expression, as precisely possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

      This method should always return a result, though it may be the best approximation that is available at the time.

      Specified by:
      getItemType in class Expression
      Returns:
      a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

    • computeCardinality

      protected int computeCardinality()
      Description copied from class: Expression
      Compute the static cardinality of this expression
      Specified by:
      computeCardinality in class Expression
      Returns:
      the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

    • computeSpecialProperties

      protected int computeSpecialProperties()
      Description copied from class: Expression
      Compute the special properties of this expression. These properties are denoted by a bit-significant integer, possible values are in class StaticProperty. The "special" properties are properties other than cardinality and dependencies, and most of them relate to properties of node sequences, for example whether the nodes are in document order.
      Overrides:
      computeSpecialProperties in class Expression
      Returns:
      the special properties, as a bit-significant integer

    • getIntrinsicDependencies

      public int getIntrinsicDependencies()
      Description copied from class: Expression
      Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".
      Overrides:
      getIntrinsicDependencies in class Expression
      Returns:
      an integer containing bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

    • copy

      public AttributeGetter copy(RebindingMap rebindings)
      Description copied from class: Expression
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.
      Returns:
      the copy of the original expression

    • addToPathMap

      public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
      Description copied from class: Expression
      Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

      The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

      Overrides:
      addToPathMap in class Expression
      Parameters:
      pathMap - the PathMap to which the expression should be added
      pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
      Returns:
      the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

    • getImplementationMethod

      public int getImplementationMethod()
      Description copied from class: Expression
      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
      Specified by:
      getImplementationMethod in class Expression
      Returns:
      the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Description copied from class: Expression
      Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
      Overrides:
      evaluateItem in class Expression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • evaluateAsString

      public UnicodeString evaluateAsString(XPathContext context) throws XPathException
      Description copied from class: Expression
      Evaluate an expression as a String. This function must only be called in contexts where it is known that the expression will return a single string (or where an empty sequence is to be treated as a zero-length string). Implementations should not attempt to convert the result to a string, other than converting () to "". This method is used mainly to evaluate expressions produced by compiling an attribute value template.
      Overrides:
      evaluateAsString in class Expression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • getExpressionName

      public String getExpressionName()
      Description copied from class: Expression
      Get a name identifying the kind of expression, in terms meaningful to a user.
      Overrides:
      getExpressionName in class Expression
      Returns:
      a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the expression.

    • toShortString

      public String toShortString()
      Description copied from class: Expression
      Produce a short string identifying the expression for use in error messages
      Overrides:
      toShortString in class Expression
      Returns:
      a short string, sufficient to identify the expression

    • toString

      public String toString()
      Description copied from class: Expression

      The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.

      For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression. The expression produced should be equivalent to the original making certain assumptions about the static context. In general the expansion will make no assumptions about namespace bindings, except that (a) the prefix "xs" is used to refer to the XML Schema namespace, and (b) the default function namespace is assumed to be the "fn" namespace.

      In the case of XSLT instructions and XQuery expressions, the toString() method gives an abstracted view of the syntax that is not designed in general to be parseable.

      Overrides:
      toString in class Expression
      Returns:
      a representation of the expression as a string

    • equals

      public boolean equals(Object obj)
      Description copied from class: Expression
      The equals() test for expressions returns true if it can be determined that two expressions (given their static context) will return the same result in all circumstances. The value false is returned if this is not the case or if it cannot be determined to be the case.

      During the various phases of compilation, expression objects are mutable. Changing an expression may change its hashCode, and may change the result of equals() comparisons. Expressions should therefore not be held in data structures such as maps and sets that depend on equality comparison unless they are no longer subject to such mutation.

      Overrides:
      equals in class Expression
      Parameters:
      obj - the other operand; the result is false if this is not an Expression
      Returns:
      true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

    • computeHashCode

      protected int computeHashCode()
      Description copied from class: Expression
      Compute a hash code, which will then be cached for later use
      Overrides:
      computeHashCode in class Expression
      Returns:
      a computed hash code

    • export

      public void export(ExpressionPresenter out)
      Description copied from class: Expression
      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Specified by:
      export in interface ExportAgent
      Specified by:
      export in class Expression
      Parameters:
      out - the expression presenter used to display the structure

    • getElaborator

      public Elaborator getElaborator()
      Make an elaborator for this expression
      Overrides:
      getElaborator in class Expression
      Returns:
      a suitable elaborator