public interface XPathEvaluator
The evaluation of XPath expressions is provided by
XPathEvaluator
. In a DOM implementation which supports the
XPath 3.0 feature, as described above, the XPathEvaluator
interface will be implemented on the same object which implements the
Document
interface permitting it to be obtained by the usual
binding-specific method such as casting or by using the DOM Level 3
getInterface method. In this case the implementation obtained from the
Document supports the XPath DOM module and is compatible with the XPath
1.0 specification.
Evaluation of expressions with specialized extension functions or
variables may not work in all implementations and is, therefore, not
portable. XPathEvaluator
implementations may be available
from other sources that could provide specific support for specialized
extension functions or variables as would be defined by other
specifications.
See also the Document Object Model (DOM) Level 3 XPath Specification.
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Method Summary
Modifier and TypeMethodDescriptioncreateExpression
(String expression, XPathNSResolver resolver) Creates a parsed XPath expression with resolved namespaces.createNSResolver
(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.evaluate
(String expression, Node contextNode, XPathNSResolver resolver, short type, Object result) Evaluates an XPath expression string and returns a result of the specified type if possible.
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Method Details
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createExpression
XPathExpression createExpression(String expression, XPathNSResolver resolver) throws XPathException, 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
- Theresolver
permits translation of prefixes within the XPath expression into appropriate namespace URIs . If this is specified asnull
, any namespace prefix within the expression will result inDOMException
being thrown with the codeNAMESPACE_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 theXPathEvaluator
iDOMException
- NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specifiedXPathNSResolver
.
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createNSResolver
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 methodlookupNamespaceURI
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.
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evaluate
Object evaluate(String expression, Node contextNode, XPathNSResolver resolver, short type, Object result) throws XPathException, 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
- Thecontext
is context node for the evaluation of this XPath expression. If the XPathEvaluator was obtained by casting theDocument
then this must be owned by the same document and must be aDocument
,Element
,Attribute
,Text
,CDATASection
,Comment
,ProcessingInstruction
, orXPathNamespace
node. If the context node is aText
or aCDATASection
, 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
- Theresolver
permits translation of prefixes within the XPath expression into appropriate namespace URIs . If this is specified asnull
, any namespace prefix within the expression will result inDOMException
being thrown with the codeNAMESPACE_ERR
.type
- If a specifictype
is specified, then the result will be returned as the corresponding type.For XPath 1.0 results, this must be one of the codes of theXPathResult
interface.result
- Theresult
specifies a specific result object which may be reused and returned by this method. If this is specified asnull
or 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 typeXPathResult
.- 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 theXPathEvaluator
i
TYPE_ERR: Raised if the result cannot be converted to return the specified type.DOMException
- NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specifiedXPathNSResolver
.
WRONG_DOCUMENT_ERR: The Node is from a document that is not supported by thisXPathEvaluator
.
NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath context node or the request type is not permitted by thisXPathEvaluator
.
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