org.apache.xpath.domapi
Class XPathEvaluatorImpl

java.lang.Object
  org.apache.xpath.domapi.XPathEvaluatorImpl

public final class XPathEvaluatorImpl
extends java.lang.Object

The class provides an implementation of XPathEvaluator according to the DOM L3 XPath Specification, Working Group Note 26 February 2004.

See also the Document Object Model (DOM) Level 3 XPath Specification.

The evaluation of XPath expressions is provided by XPathEvaluator, which will provide evaluation of XPath 1.0 expressions with no specialized extension functions or variables. It is expected that the XPathEvaluator interface will be implemented on the same object which implements the Document interface in an implementation which supports the XPath DOM module. XPathEvaluator implementations may be available from other sources that may provide support for special extension functions or variables which are not defined in this specification.

See Also:

org.w3c.dom.xpath.XPathEvaluator

Nested Class Summary

private static class

XPathEvaluatorImpl.DummyPrefixResolver This prefix resolver is created whenever null is passed to the evaluate method.

Field Summary

private org.w3c.dom.Document

m_doc The document to be searched to parallel the case where the XPathEvaluator is obtained by casting a Document.

Constructor Summary

XPathEvaluatorImpl()
Constructor in the case that the XPath expression can be evaluated without needing an XML document at all.

XPathEvaluatorImpl(org.w3c.dom.Document doc)
Constructor for XPathEvaluatorImpl.

Method Summary

XPathExpression	createExpression(java.lang.String expression, XPathNSResolver resolver) Creates a parsed XPath expression with resolved namespaces.
XPathNSResolver	createNSResolver(org.w3c.dom.Node nodeResolver) Adapts any DOM node to resolve namespaces so that an XPath expression can be easily evaluated relative to the context of the node where it appeared within the document.
java.lang.Object	evaluate(java.lang.String expression, org.w3c.dom.Node contextNode, XPathNSResolver resolver, short type, java.lang.Object result) Evaluates an XPath expression string and returns a result of the specified type if possible.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

m_doc

private final org.w3c.dom.Document m_doc

The document to be searched to parallel the case where the XPathEvaluator is obtained by casting a Document.

Constructor Detail

XPathEvaluatorImpl

public XPathEvaluatorImpl(org.w3c.dom.Document doc)

Constructor for XPathEvaluatorImpl.

Parameters:

doc - The document to be searched, to parallel the case where'' the XPathEvaluator is obtained by casting the document.

XPathEvaluatorImpl

public XPathEvaluatorImpl()

Constructor in the case that the XPath expression can be evaluated without needing an XML document at all.

Method Detail

createExpression

public XPathExpression createExpression(java.lang.String expression,
                                        XPathNSResolver resolver)
                                 throws XPathException,
                                        org.w3c.dom.DOMException

Creates a parsed XPath expression with resolved namespaces. This is useful when an expression will be reused in an application since it makes it possible to compile the expression string into a more efficient internal form and preresolve all namespace prefixes which occur within the expression.

Parameters:

expression - The XPath expression string to be parsed.

resolver - The resolver permits translation of prefixes within the XPath expression into appropriate namespace URIs . If this is specified as null, any namespace prefix within the expression will result in DOMException being thrown with the code NAMESPACE_ERR.

Returns:

The compiled form of the XPath expression.

Throws:

XPathException - INVALID_EXPRESSION_ERR: Raised if the expression is not legal according to the rules of the XPathEvaluatori

org.w3c.dom.DOMException - NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specified XPathNSResolver.

See Also:

org.w3c.dom.xpath.XPathEvaluator#createExpression(String, XPathNSResolver)

createNSResolver

public XPathNSResolver createNSResolver(org.w3c.dom.Node nodeResolver)

Adapts any DOM node to resolve namespaces so that an XPath expression can be easily evaluated relative to the context of the node where it appeared within the document. This adapter works like the DOM Level 3 method lookupNamespaceURI on nodes in resolving the namespaceURI from a given prefix using the current information available in the node's hierarchy at the time lookupNamespaceURI is called, also correctly resolving the implicit xml prefix.

Parameters:

nodeResolver - The node to be used as a context for namespace resolution.

Returns:

XPathNSResolver which resolves namespaces with respect to the definitions in scope for a specified node.

See Also:

org.w3c.dom.xpath.XPathEvaluator#createNSResolver(Node)

evaluate

public java.lang.Object evaluate(java.lang.String expression,
                                 org.w3c.dom.Node contextNode,
                                 XPathNSResolver resolver,
                                 short type,
                                 java.lang.Object result)
                          throws XPathException,
                                 org.w3c.dom.DOMException

Evaluates an XPath expression string and returns a result of the specified type if possible.

Parameters:

expression - The XPath expression string to be parsed and evaluated.

contextNode - The context is context node for the evaluation of this XPath expression. If the XPathEvaluator was obtained by casting the Document then this must be owned by the same document and must be a Document, Element, Attribute, Text, CDATASection, Comment, ProcessingInstruction, or XPathNamespace node. If the context node is a Text or a CDATASection, then the context is interpreted as the whole logical text node as seen by XPath, unless the node is empty in which case it may not serve as the XPath context.

resolver - The resolver permits translation of prefixes within the XPath expression into appropriate namespace URIs . If this is specified as null, any namespace prefix within the expression will result in DOMException being thrown with the code NAMESPACE_ERR.

type - If a specific type is specified, then the result will be coerced to return the specified type relying on XPath type conversions and fail if the desired coercion is not possible. This must be one of the type codes of XPathResult.

result - The result specifies a specific result object which may be reused and returned by this method. If this is specified as nullor the implementation does not reuse the specified result, a new result object will be constructed and returned.For XPath 1.0 results, this object will be of type XPathResult.

Returns:

The result of the evaluation of the XPath expression.For XPath 1.0 results, this object will be of type XPathResult.

Throws:

XPathException - INVALID_EXPRESSION_ERR: Raised if the expression is not legal according to the rules of the XPathEvaluatori
TYPE_ERR: Raised if the result cannot be converted to return the specified type.

org.w3c.dom.DOMException - NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specified XPathNSResolver.
WRONG_DOCUMENT_ERR: The Node is from a document that is not supported by this XPathEvaluator.
NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath context node.

See Also:

org.w3c.dom.xpath.XPathEvaluator#evaluate(String, Node, XPathNSResolver, short, XPathResult)