Class XPathEvaluator

java.lang.Object
net.sf.saxon.xpath.XPathEvaluator
All Implemented Interfaces:
XPath
public class XPathEvaluator extends Object implements XPath

XPathEvaluator implements the JAXP API for standalone XPath processing (that is, executing XPath expressions in the absence of an XSLT stylesheet). It is an implementation of the JAXP 1.3 XPath interface, with additional methods provided (a) for backwards compatibility (b) to give extra control over the XPath evaluation, and (c) to support XPath 2.0.

It is intended to evolve this so that it only supports the JAXP style of operation. Some of the methods are therefore marked as deprecated in this release, and will be dropped in a future release.

For an alternative XPath API, offering more direct access to Saxon capabilities, see XPathEvaluator.

Note that the XPathEvaluator links to a Saxon Configuration object. By default a new Configuration is created automatically. In many applications, however, it is desirable to share a configuration. The default configuration is not schema aware. All source documents used by XPath expressions under this evaluator must themselves be built using the Configuration used by this evaluator.

Author:
Michael H. Kay

  • Constructor Details

    • XPathEvaluator

      public XPathEvaluator()
      Default constructor. Creates an XPathEvaluator with Configuration appropriate to the version of the Saxon software being run.

    • XPathEvaluator

      public XPathEvaluator(Configuration config)
      Construct an XPathEvaluator with a specified configuration.
      Parameters:
      config - the configuration to be used. If schema-aware XPath expressions are to be used, this must be an EnterpriseConfiguration.

    • XPathEvaluator

      public XPathEvaluator(Source source) throws XPathException
      Construct an XPathEvaluator to process a particular source document. This is equivalent to using the default constructor and immediately calling setSource().
      Parameters:
      source - The source document (or a specific node within it).
      Throws:
      XPathException

  • Method Details

    • getConfiguration

      public Configuration getConfiguration()
      Get the Configuration used by this XPathEvaluator
      Returns:
      the Configuration used by this XPathEvaluator

    • setStripSpace

      public void setStripSpace(boolean strip)
      Deprecated.
      since 8.9. The preferred way to define options for the way in which source documents are built is to use the class AugmentedSource for any of the methods expecting a Source object.
      Indicate whether all whitespace text nodes in the source document are to be removed. This option has no effect unless it is called before the call on setSource(), and unless the Source supplied to setSource() is a SAXSource or StreamSource.
      Parameters:
      strip - True if all whitespace text nodes are to be stripped from the source document, false otherwise. The default if the method is not called is false.

    • setSource

      public NodeInfo setSource(Source source) throws XPathException
      Supply a document against which XPath expressions are to be executed, converting it to a Saxon NodeInfo object.

      If the supplied source is a NodeInfo, it is returned unchanged.

      If the supplied source is a DOMSource, the result is a Saxon NodeInfo wrapper around the DOM Node contained by the DOMSource.

      In all other cases, the result is a document node, and is the same as the result of calling Configuration.buildDocument(javax.xml.transform.Source) with the same argument; except that when whitespace stripping has been requested using setStripSpace(boolean), this request is passed on.

      Despite the name of this method, it does not change the state of the XPathEvaluator in any way.

      Parameters:
      source - Any javax.xml.transform.Source object representing the document against which XPath expressions will be executed. Note that a Saxon DocumentInfo (indeed any NodeInfo) can be used as a Source. To use a third-party DOM Document as a source, create an instance of DOMSource to wrap it.

      The Source object supplied also determines the initial setting of the context item. In most cases the context node will be the root of the supplied document; however, if a NodeInfo or DOMSource is supplied it can be any node in the document.

      Returns:
      the NodeInfo of the start node in the resulting document object.
      Throws:
      XPathException - if the supplied Source is a NodeInfo object that was built using an incompatible Configuration (that is, a Configuration using a different NamePool). Also, if any error occurs parsing the document supplied as the Source.
      XPathException

    • setStaticContext

      public void setStaticContext(JAXPXPathStaticContext context)
      Set the static context for compiling XPath expressions. This provides control over the environment in which the expression is compiled, for example it allows namespace prefixes to be declared, variables to be bound and functions to be defined. For most purposes, the static context can be defined by providing and tailoring an instance of the JAXPXPathStaticContext class. Until this method is called, a default static context is used, in which no namespaces are defined other than the standard ones (xml, xslt, and saxon), and no variables or functions (other than the core XPath functions) are available.
      Parameters:
      context - the static context
      Throws:
      IllegalArgumentException - if the supplied static context uses a different and incompatible Configuration from the one used in this XPathEvaluator

    • getStaticContext

      public JAXPXPathStaticContext getStaticContext()
      Get the current static context
      Returns:
      the static context

    • createExpression

      public XPathExpressionImpl createExpression(String expression) throws XPathException
      Deprecated.
      since Saxon 8.9 - use compile(String)
      Prepare an XPath expression for subsequent evaluation.
      Parameters:
      expression - The XPath expression to be evaluated, supplied as a string.
      Returns:
      an XPathExpression object representing the prepared expression
      Throws:
      XPathException - if the syntax of the expression is wrong, or if it references namespaces, variables, or functions that have not been declared.

    • setContextNode

      public void setContextNode(NodeInfo node)
      Deprecated.
      since Saxon 8.9 - use the various method defined in the JAXP interface definition, which allow a NodeInfo object to be supplied as the value of the Source argument
      Set the context node. This provides the context node for any expressions executed after this method is called, including expressions that were prepared before it was called.
      Parameters:
      node - The node to be used as the context node. The node must be within a tree built using the same Saxon Configuration as used by this XPathEvaluator.
      Throws:
      IllegalArgumentException - if the supplied node was built using the wrong Configuration

    • reset

      public void reset()
      Specified by:
      reset in interface XPath

    • setBackwardsCompatible

      public void setBackwardsCompatible(boolean compatible)
      Set XPath 1.0 compatibility mode on or off (by default, it is false). This applies to any XPath expression compiled while this option is in force.
      Parameters:
      compatible - true if XPath 1.0 compatibility mode is to be set to true, false if it is to be set to false.

    • isBackwardsCompatible

      public boolean isBackwardsCompatible()
      Get the value of XPath 1.0 compatibility mode
      Returns:
      true if XPath 1.0 compatibility mode is set

    • setXPathVariableResolver

      public void setXPathVariableResolver(XPathVariableResolver xPathVariableResolver)
      Set the resolver for XPath variables
      Specified by:
      setXPathVariableResolver in interface XPath
      Parameters:
      xPathVariableResolver - a resolver for variables

    • getXPathVariableResolver

      public XPathVariableResolver getXPathVariableResolver()
      Get the resolver for XPath variables
      Specified by:
      getXPathVariableResolver in interface XPath
      Returns:
      the resolver, if one has been set

    • setXPathFunctionResolver

      public void setXPathFunctionResolver(XPathFunctionResolver xPathFunctionResolver)
      Set the resolver for XPath functions
      Specified by:
      setXPathFunctionResolver in interface XPath
      Parameters:
      xPathFunctionResolver - a resolver for XPath function calls

    • getXPathFunctionResolver

      public XPathFunctionResolver getXPathFunctionResolver()
      Get the resolver for XPath functions
      Specified by:
      getXPathFunctionResolver in interface XPath
      Returns:
      the resolver, if one has been set

    • setNamespaceContext

      public void setNamespaceContext(NamespaceContext namespaceContext)
      Set the namespace context to be used.
      Specified by:
      setNamespaceContext in interface XPath
      Parameters:
      namespaceContext - The namespace context

    • getNamespaceContext

      public NamespaceContext getNamespaceContext()
      Get the namespace context, if one has been set using setNamespaceContext(NamespaceContext)
      Specified by:
      getNamespaceContext in interface XPath
      Returns:
      the namespace context if set, or null otherwise

    • importSchema

      public void importSchema(Source source) throws SchemaException
      Import a schema. This is possible only if Saxon-EE is being used, and if the Configuration is an EnterpriseConfiguration. Having imported a schema, the types defined in that schema become part of the static context.
      Parameters:
      source - A Source object identifying the schema document to be loaded
      Throws:
      SchemaException - if the schema contained in this document is invalid
      UnsupportedOperationException - if the configuration is not schema-aware

    • compile

      public XPathExpression compile(String expr) throws XPathExpressionException
      Compile an XPath 2.0 expression
      Specified by:
      compile in interface XPath
      Parameters:
      expr - the XPath 2.0 expression to be compiled, as a string
      Returns:
      the compiled form of the expression
      Throws:
      XPathExpressionException - if there are any static errors in the expression. Note that references to undeclared variables are not treated as static errors, because variables are not pre-declared using this API.

    • evaluate

      public Object evaluate(String expr, Object node, QName qName) throws XPathExpressionException
      Single-shot method to compile and execute an XPath 2.0 expression.
      Specified by:
      evaluate in interface XPath
      Parameters:
      expr - The XPath 2.0 expression to be compiled and executed
      node - The context node for evaluation of the expression.

      This may be a NodeInfo object, representing a node in Saxon's native implementation of the data model, or it may be a node in any supported external object model: DOM, JDOM, DOM4J, or XOM, or any other model for which support has been configured in the Configuration. Note that the supporting libraries for the chosen model must be on the class path.

      Contrary to the interface specification, Saxon does not supply an empty document when the value is null. This is because Saxon supports multiple object models, and it's unclear what kind of document node would be appropriate. Instead, Saxon uses the node supplied to the setContextNode(NodeInfo) method if available, and if none is available, executes the XPath expression with the context item undefined.

      qName - The type of result required. For details, see XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)
      Returns:
      the result of evaluating the expression, returned as described in XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)
      Throws:
      XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.

    • evaluate

      public String evaluate(String expr, Object node) throws XPathExpressionException
      Single-shot method to compile an execute an XPath 2.0 expression, returning the result as a string.
      Specified by:
      evaluate in interface XPath
      Parameters:
      expr - The XPath 2.0 expression to be compiled and executed
      node - The context node for evaluation of the expression

      This may be a NodeInfo object, representing a node in Saxon's native implementation of the data model, or it may be a node in any supported external object model: DOM, JDOM, DOM4J, or XOM, or any other model for which support has been configured in the Configuration. Note that the supporting libraries for the chosen model must be on the class path.

      Contrary to the interface specification, Saxon does not supply an empty document when the value is null. This is because Saxon supports multiple object models, and it's unclear what kind of document node would be appropriate. Instead, Saxon uses the node supplied to the setContextNode(NodeInfo) method if available, and if none is available, executes the XPath expression with the context item undefined.

      Returns:
      the result of evaluating the expression, converted to a string as if by calling the XPath string() function
      Throws:
      XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.

    • evaluate

      public Object evaluate(String expr, InputSource inputSource, QName qName) throws XPathExpressionException
      Single-shot method to parse and build a source document, and compile an execute an XPath 2.0 expression, against that document
      Specified by:
      evaluate in interface XPath
      Parameters:
      expr - The XPath 2.0 expression to be compiled and executed
      inputSource - The source document: this will be parsed and built into a tree, and the XPath expression will be executed with the root node of the tree as the context node.
      qName - The type of result required. For details, see XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)
      Returns:
      the result of evaluating the expression, returned as described in XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)
      Throws:
      XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.
      NullPointerException - if any of the three arguments is null

    • evaluate

      public String evaluate(String expr, InputSource inputSource) throws XPathExpressionException
      Single-shot method to parse and build a source document, and compile an execute an XPath 2.0 expression, against that document, returning the result as a string
      Specified by:
      evaluate in interface XPath
      Parameters:
      expr - The XPath 2.0 expression to be compiled and executed
      inputSource - The source document: this will be parsed and built into a tree, and the XPath expression will be executed with the root node of the tree as the context node
      Returns:
      the result of evaluating the expression, converted to a string as if by calling the XPath string() function
      Throws:
      XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.
      NullPointerException - if either of the two arguments is null

    • main

      public static void main(String[] args) throws Exception
      A simple command-line interface for the XPathEvaluator (not documented).
      Parameters:
      args - command line arguments. First parameter is the filename containing the source document, second parameter is the XPath expression.
      Throws:
      Exception - if any error occurs