/*
* Copyright (c) 2002 World Wide Web Consortium,
* (Massachusetts Institute of Technology, Institut National de
* Recherche en Informatique et en Automatique, Keio University). All
* Rights Reserved. This program is distributed under the W3C's Software
* Intellectual Property License. This program is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY; without even
* the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE.
* See W3C License http://www.w3.org/Consortium/Legal/ for more details.
*/
package org.w3c.dom.xpath;
import org.w3c.dom.Node;
import org.w3c.dom.DOMException;
/**
* <strong>DOM Level 3 WD Experimental:
* The DOM Level 3 specification is at the stage
* of Working Draft, which represents work in
* progress and thus may be updated, replaced,
* or obsoleted by other documents at any time.</strong> <p>
* <code>XPathEvaluator</code>, which will provide evaluation of XPath 1.0
* expressions with no specialized extension functions or variables. It is
* expected that the <code>XPathEvaluator</code> interface will be
* implemented on the same object which implements the <code>Document</code>
* interface in an implementation which supports the XPath DOM module.
* <code>XPathEvaluator</code> implementations may be available from other
* sources that may provide support for special extension functions or
* variables which are not defined in this specification. The methods of
* XPathExpression should be named with more-XPath- specific names because
* the interface will often be implemented by the same object which
* implements document.No change.The point of interfaces is to localize the
* implementing namespace. This would make the method names unnecessarily
* long and complex even though there are no conflicts in the interface
* itself. The new core method getInterface is designed for discovering
* interfaces of additional modules that may not be directly implemented on
* the objects to which they are attached. This could be used to implement
* XPath on a separate object. The user only refers to the separate
* interfaces and not the proprietary aggregate implementation.Should entity
* refs be supported so that queries can be made on them?No change.We will
* not do this now. They are not part of the XPath data model. Note that
* they may be present in the hierarchy of returned nodes, but may not
* directly be requested or returned in the node set.What does createResult
* create when one wants to reuse the XPath?It is not useful.Removed method.
* Should ordering be a separate flag, or a type of result that can be
* requested. As a type of result, it can be better optimized in
* implementations.It makes sense as a type of result. Changed.Removed
* method.Implementing XPathEvaluator on Document can be a problem due to
* conflicts in the names of the methods.The working group finds no better
* solution. GetInterface in Level 3 permits the object to be implemented
* separately. We should be committed to this. We will leave this issue open
* to see if we get more feedback on it.How does this interface adapt to
* XPath 2.0 and other query languages.No change.This interface is not
* intended to adapt to XPath 2.0 or other languages. The models of these
* are likely to be incompatible enough to require new APIs.For alternate
* implementations that can use this API, it can be obtained from different
* sources.Support for custom variables and functions would be very useful.
* No change.It is possible for an implementation to supply alternative
* sources of an XPathEvaluator that can be customized with a custom
* variable and function context. We do not specify how this is
* accomplished. It is too complex to address in this version of the XPath
* DOM.
* <p>See also the <a href='http://www.w3.org/TR/2002/WD-DOM-Level-3-XPath-20020328'>Document Object Model (DOM) Level 3 XPath Specification</a>.
*/
public interface XPathEvaluator {
/**
* 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.createExpression should not raise
* exceptions about type coercion.This was already fixed in the public
* draft.
* @param expression The XPath expression string to be parsed.
* @param resolver The <code>resolver</code> permits translation of
* prefixes within the XPath expression into appropriate namespace URIs
* . If this is specified as <code>null</code>, any namespace prefix
* within the expression will result in <code>DOMException</code>
* being thrown with the code <code>NAMESPACE_ERR</code>.
* @return The compiled form of the XPath expression.
* @exception XPathException
* INVALID_EXPRESSION_ERR: Raised if the expression is not legal
* according to the rules of the <code>XPathEvaluator</code>i
* @exception org.w3c.dom.DOMException
* NAMESPACE_ERR: Raised if the expression contains namespace prefixes
* which cannot be resolved by the specified
* <code>XPathNSResolver</code>.
*/
public XPathExpression createExpression(String expression,
XPathNSResolver resolver)
throws XPathException, DOMException;
/**
* 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 by calling the
* method <code>lookupNamespacePrefix</code> on <code>Node</code>.It
* should be possible to create an XPathNSResolver that does not rely on
* a node, but which implements a map of resolutions that can be added
* to by the application.No change.The application can easily create
* this, which was why the interface was designed as it is. The
* specification will not require a specific factory at this time for
* application populated maps.There should be type restrictions on which
* types of nodes may be adapted by createNSResolver.No change.The
* namespace methods on the Node interface of the Level 3 core may be
* called without exception on all node types. In some cases no non-null
* namespace resolution will ever be returned. That is what may also be
* expected of this adapter.
* @param nodeResolver The node to be used as a context for namespace
* resolution.
* @return <code>XPathNSResolver</code> which resolves namespaces with
* respect to the definitions in scope for a specified node.
*/
public XPathNSResolver createNSResolver(Node nodeResolver);
/**
* Evaluates an XPath expression string and returns a result of the
* specified type if possible.An exception needs to be raised when an
* XPath expression is evaluated on a node such as an EntityReference
* which cannot serve as an XPath context node.Done: NOT_SUPPORTED_ERR.A
* description is needed of what happens when the node passed to the
* evaluation function is a Text or CDATASection in the DOM case where
* the text may be fragmented between text nodes.Done.Eliminate the
* evaluate method from XPathEvaluator, forcing everyone to create
* expressions.No change.Any implementor can easily implement it by
* creating an expression. Having it available as a separate routine is
* a convenience and may be an optimization as well in some cases.Revert
* to multiple evaluateAs methods instead of passing a type code.No
* change.This is an alternative which eliminates a method argument
* while adding methods, but the type code is used to designate the type
* on returns anyway and using it as an argument to specify any coercion
* seems natural to many.Error exceptions are needed when there is a
* mismatch between the implementation of XPathEvaluator and the context
* node being evaluated.Done: WRONG_DOCUMENT_ERRConcern that the XPath
* API should only support natural results of XPath expression, without
* convenience coercion or alternative representations. Any special
* thing such as ordering should be added later to resultNo change.We
* have significant use cases for returning alternative types and
* representations by explicit request in advance.Eliminate the reusable
* result argument.No change.No. We have use cases for it, and there is
* already an implementation showing there is nothing wrong with it.
* State that the XPathNSResolver argument may be a function in
* Javascript.Yes.There is an exception when there is a problem parsing
* the expression, but none when there is a problem evaluating the
* expression.No change.If the expression parsing was OK, then the worst
* that can happen is an empty result is returned.When requesting any
* type, the implementation should be permitted to return any type of
* node set, i.e. ordered or unordered, it finds convenient.No change.
* The iterator it returns may contain ordered results, but identifying
* it as such produces undesirable results, because it would create
* complexity for the user -- requiring checking two types to see if the
* result was a node set -- or incompatibility caused by assuming it was
* always the one returned by a particular implementation the developer
* was using.NAMESPACE_ERR description is not appropriate to the way it
* is being used here.Make the description of NAMESPACE_ERR in the core
* specification more general.Should the INVALID_EXPRESSION_ERR be
* INVALID_SYNTAX_ERR?No change.We can improve the description of the
* error, but the name is appropriate as-is. It covers not only syntax
* errors but expression errors, such as when the implementation has no
* custom functions or variables but the expression specifies custom
* functions or variables.
* @param expression The XPath expression string to be parsed and
* evaluated.
* @param contextNode The <code>context</code> is context node for the
* evaluation of this XPath expression. If the XPathEvaluator was
* obtained by casting the <code>Document</code> then this must be
* owned by the same document and must be a <code>Document</code>,
* <code>Element</code>, <code>Attribute</code>, <code>Text</code>,
* <code>CDATASection</code>, <code>Comment</code>,
* <code>ProcessingInstruction</code>, or <code>XPathNamespace</code>
* node. If the context node is a <code>Text</code> or a
* <code>CDATASection</code>, 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.
* @param resolver The <code>resolver</code> permits translation of
* prefixes within the XPath expression into appropriate namespace URIs
* . If this is specified as <code>null</code>, any namespace prefix
* within the expression will result in <code>DOMException</code>
* being thrown with the code <code>NAMESPACE_ERR</code>.
* @param type If a specific <code>type</code> 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
* <code>XPathResult</code>.
* @param result The <code>result</code> specifies a specific
* <code>XPathResult</code> which may be reused and returned by this
* method. If this is specified as <code>null</code>or the
* implementation cannot reuse the specified result, a new
* <code>XPathResult</code> will be constructed and returned.
* @return The result of the evaluation of the XPath expression.
* @exception XPathException
* INVALID_EXPRESSION_ERR: Raised if the expression is not legal
* according to the rules of the <code>XPathEvaluator</code>i
* <br>TYPE_ERR: Raised if the result cannot be converted to return the
* specified type.
* @exception org.w3c.dom.DOMException
* NAMESPACE_ERR: Raised if the expression contains namespace prefixes
* which cannot be resolved by the specified
* <code>XPathNSResolver</code>.
* <br>WRONG_DOCUMENT_ERR: The Node is from a document that is not
* supported by this XPathEvaluator.
* <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath
* context node.
*/
public Object evaluate(String expression,
Node contextNode,
XPathNSResolver resolver,
short type,
Object result)
throws XPathException, DOMException;
}