net.sf.saxon.xpath
public class XPathExpressionImpl extends Object implements XPathExpression, SortKeyEvaluator
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.
Constructor Summary | |
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protected | XPathExpressionImpl(Expression exp, Executable exec)
The constructor is protected, to ensure that instances can only be
created using the createExpression() method of XPathEvaluator |
Method Summary | |
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List | evaluate()
Execute a prepared XPath expression, returning the results as a List. |
Object | evaluate(Object node, QName qName)
JAXP 1.3 evaluate() method |
String | evaluate(Object node)
Evaluate the expression to return a string value |
Object | evaluate(InputSource inputSource, QName qName)
Evaluate the XPath expression against an input source to obtain a result of a specified type |
String | evaluate(InputSource inputSource)
Evaluate the XPath expression against an input source to obtain a string result |
Object | evaluateSingle()
Execute a prepared XPath expression, returning the first item in the result.
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Item | evaluateSortKey(int n, XPathContext c)
Callback for evaluating the sort keys. |
Configuration | getConfiguration()
Get the Configuration under which this XPath expression was compiled |
Expression | getInternalExpression()
Low-level method to get the internal Saxon expression object. |
SlotManager | getStackFrameMap()
Get the stack frame map. |
protected void | privatelySetContextNode(NodeInfo node)
Protected, undeprecated version of setContextNode() for use by deprecated paths within the package
(exists to avoid deprecation warnings when compiling Saxon) |
SequenceIterator | rawIterator(Item contextItem)
Get a raw iterator over the results of the expression. |
void | setContextNode(NodeInfo node)
Set the context node for evaluating the expression. |
void | setSortKey(XPathExpressionImpl sortKey)
Define the sort order for the results of the expression. |
protected void | setStackFrameMap(SlotManager map)
Define the number of slots needed for local variables within the expression.
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Parameters: exp the compiled expression exec the executable
Deprecated: since 9.0. This method is not present in the JAXP interface. Either use the JAXP methods such as XPathExpressionImpl, or use the Saxon XPath API instead of JAXP.
Execute a prepared XPath expression, returning the results as a List. The context node must have been set previously using setContextNode.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 XPathExpressionImpl with the second argument set to NODESET.
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, DOM4J, JDOM, or XOM, provided the support module for that object model is loaded.
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 XPathExpressionImpl method if available, and if none
is available, executes the XPath expression with the context item undefined.
Saxon does not allow a NodeList to be supplied for this parameter. It's not clear what this would be intended to mean.
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:
QName Return 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.
If the first argument is a wrapper around a DOM Node, then the result is
returned as a DOM NodeList, and an exception is then thrown if the result sequence
contains a value that is not a DOM Node. In all other cases
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).
Throws: XPathExpressionException if evaluation of the expression fails or if the result cannot be converted to the requested type.
Parameters: node the initial context node. This must be either an instance of NodeInfo or a node
recognized by a known external object model.
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 XPathExpressionImpl method if available, and if none
is available, executes the XPath expression with the context item undefined.
Returns: the results of the expression, converted to a String
Throws: XPathExpressionException if evaluation fails
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.) If the supplied value is null then (contrary to the JAXP specifications), the XPath expression is evaluated with the context item undefined. 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 XPathExpressionImpl
Throws: XPathExpressionException
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 in the event of an XPath dynamic error NullPointerException If inputSource
is null
.
Deprecated: since 9.0. This method is not present in the JAXP interface. Either use the JAXP methods such as XPathExpressionImpl, or use the Saxon XPath API instead of JAXP.
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.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
Returns: the Saxon configuration
Returns: the underlying Saxon expression object.
Returns: a description of the stack frame
Parameters: node the context node
Parameters: contextItem the context item for evaluating the expression
Returns: an iterator over the results of the expression, with no conversion of returned items
Since: 9.0
Deprecated: since 9.0. Using this method is not thread-safe. Use a method instead such as XPathExpressionImpl that allows the context node to be specified as a parameter to the call.
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.Parameters: node the context node
Deprecated: since 9.0. This method is not present in the JAXP interface. The recommended way to get a sorted result is to use XQuery instead of XPath.
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. Note that the expression is not automatically atomized; if it selects nodes, these should be explicitly converted to atomic values by calling the string() or data() functions.
Parameters: map description of the stack frame