Class XPathExpressionImpl

java.lang.Object
net.sf.saxon.xpath.XPathExpressionImpl
All Implemented Interfaces:
XPathExpression

public class XPathExpressionImpl extends Object implements XPathExpression

The JAXP XPathExpression interface represents a compiled XPath expression that can be repeatedly evaluated. This class is Saxon's implementation of that interface.

The class also includes some methods retained from Saxon's original XPath API. When these methods are used, the object contains the context node and other state, so it is not thread-safe.

Author:
Michael H. Kay
  • Constructor Details

    • XPathExpressionImpl

      protected XPathExpressionImpl(Expression exp, Configuration config)
      The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator
  • Method Details

    • setStackFrameMap

      protected void setStackFrameMap(SlotManager map)
      Define the number of slots needed for local variables within the expression. This method is for internal use only.
    • getStackFrameMap

      public SlotManager getStackFrameMap()
      Get the stack frame map. This holds information about the allocation of slots to variables. This is needed by applications using low-level interfaces for evaluating the expression
    • getConfiguration

      public Configuration getConfiguration()
      Get the Configuration under which this XPath expression was compiled
    • setSortKey

      public void setSortKey(XPathExpressionImpl sortKey)
      Define the sort order for the results of the expression. If this method is called, then the list returned by a subsequent call on the evaluate() method will first be sorted.
      Parameters:
      sortKey - an XPathExpression, which will be applied to each item in the sequence; the result of this expression determines the ordering of the list returned by the evaluate() method. The sortKey can be null, to clear a previous sort key.
    • setContextNode

      public void setContextNode(NodeInfo node)
      Set the context node for evaluating the expression. If this method is not called, the context node will be the root of the document to which the prepared expression is bound.
    • evaluate

      public List evaluate() throws XPathException
      Execute a prepared XPath expression, returning the results as a List. The context node must have been set previously using setContextNode(net.sf.saxon.om.NodeInfo).
      Returns:
      The results of the expression, as a List. The List represents the sequence of items returned by the expression. Each item in the list will either be an instance of net.sf.saxon.om.NodeInfo, representing a node, or a Java object representing an atomic value. For the types of Java object that may be returned, see evaluate(Object, javax.xml.namespace.QName) with the second argument set to NODESET.
      Throws:
      XPathException
    • evaluateSingle

      public Object evaluateSingle() throws XPathException
      Execute a prepared XPath expression, returning the first item in the result. This is useful where it is known that the expression will only return a singleton value (for example, a single node, or a boolean). The context node must be set previously using setContextNode(net.sf.saxon.om.NodeInfo).
      Returns:
      The first item in the sequence returned by the expression. If the expression returns an empty sequence, this method returns null. Otherwise, it returns the first item in the result sequence, represented as a Java object using the same mapping as for the evaluate() method
      Throws:
      XPathException
    • rawIterator

      public SequenceIterator rawIterator() throws XPathException
      Get a raw iterator over the results of the expression. This returns results without any conversion of the returned items to "native" Java classes. This method is intended for use by applications that need to process the results of the expression using internal Saxon interfaces.
      Throws:
      XPathException
    • evaluate

      public Object evaluate(Object node, QName qName) throws XPathExpressionException
      JAXP 1.3 evaluate() method
      Specified by:
      evaluate in interface XPathExpression
      Parameters:
      node - The context node. This must use a representation of nodes that this implementation understands. This may be a Saxon NodeInfo, or a node in one of the external object models supported, for example DOM, JDOM, or XOM, provided the support module for that object model is loaded.
      qName - Indicates the type of result required. This must be one of the constants defined in the JAXP XPathConstants class. Saxon will attempt to convert the actual result of the expression to the required type using the XPath 1.0 conversion rules.
      Returns:
      the result of the evaluation, as a Java object of the appropriate type. Saxon interprets the rules as follows:
      QNameReturn Value
      BOOLEAN The effective boolean value of the actual result, as a Java Boolean object
      STRING The result of applying the string() function to the actual result, as a Java String object
      NUMBER The result of applying the number() function to the actual result, as a Java Double object
      NODE A single node, in the native data model supplied as input. If the expression returns more than one node, the first is returned. If the expression returns an empty sequence, null is returned. If the expression returns an atomic value, or if the first item in the result sequence is an atomic value, an exception is thrown.
      NODESET This is interpreted as allowing any sequence, of nodes or atomic values. The result is returned as a Java List object, unless it is empty, in which case null is returned. The contents of the list may be node objects (in the native data model supplied as input, or Java objects representing the XPath atomic values in the actual result: String for an xs:string, Double for a xs:double, Long for an xs:integer, and so on. (For safety, cast the values to a type such as xs:string within the XPath expression). Note that the result is never returned as a DOM NodeList.
      Throws:
      XPathExpressionException - if evaluation of the expression fails or if the result cannot be converted to the requested type.
    • evaluate

      public String evaluate(Object node) throws XPathExpressionException
      Evaluate the expression to return a string value
      Specified by:
      evaluate in interface XPathExpression
      Parameters:
      node - the initial context node. This must be an instance of NodeInfo
      Returns:
      the results of the expression, converted to a String
      Throws:
      XPathExpressionException - if evaluation fails
    • evaluate

      public Object evaluate(InputSource inputSource, QName qName) throws XPathExpressionException
      Evaluate the XPath expression against an input source to obtain a result of a specified type
      Specified by:
      evaluate in interface XPathExpression
      Parameters:
      inputSource - The input source document against which the expression is evaluated. (Note that there is no caching. This will be parsed, and the parsed result will be discarded.)
      qName - The type required, identified by a constant in XPathConstants
      Returns:
      the result of the evaluation, as a Java object of the appropriate type: see evaluate(Object, javax.xml.namespace.QName)
      Throws:
      XPathExpressionException
    • evaluate

      public String evaluate(InputSource inputSource) throws XPathExpressionException
      Evaluate the XPath expression against an input source to obtain a string result
      Specified by:
      evaluate in interface XPathExpression
      Parameters:
      inputSource - The input source document against which the expression is evaluated. (Note that there is no caching. This will be parsed, and the parsed result will be discarded.)
      Returns:
      the result of the evaluation, converted to a String
      Throws:
      XPathExpressionException
    • getInternalExpression

      public Expression getInternalExpression()
      Low-level method to get the internal Saxon expression object. This exposes a wide range of internal methods that may be needed by specialized applications, and allows greater control over the dynamic context for evaluating the expression.
      Returns:
      the underlying Saxon expression object.