XPathExpressionpublic interface XPathExpression XPathExpression provides access to compiled XPath expressions.
| Evaluation of XPath Expressions. |
| context |
If a request is made to evaluate the expression in the absence
of a context item, an empty document node will be used for the context.
For the purposes of evaluating XPath expressions, a DocumentFragment
is treated like a Document node.
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| variables |
If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}.
An {@link XPathExpressionException} is raised if the variable resolver is undefined or
the resolver returns null for the variable.
The value of a variable must be immutable through the course of any single evaluation.
|
| functions |
If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}.
An {@link XPathExpressionException} is raised if the function resolver is undefined or
the function resolver returns null for the function.
|
| QNames |
QNames in the expression are resolved against the XPath namespace context.
|
| result |
This result of evaluating an expression is converted to an instance of the desired return type.
Valid return types are defined in {@link XPathConstants}.
Conversion to the return type follows XPath conversion rules.
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An XPath expression is not thread-safe and not reentrant.
In other words, it is the application's responsibility to make
sure that one {@link XPathExpression} object is not used from
more than one thread at any given time, and while the evaluate
method is invoked, applications may not recursively call
the evaluate method.
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| Methods Summary |
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| public java.lang.Object | evaluate(java.lang.Object item, javax.xml.namespace.QName returnType)Evaluate the compiled XPath expression in the specified context and return the result as the specified type.
See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.
If returnType is not one of the types defined in {@link XPathConstants},
then an IllegalArgumentException is thrown.
If a null value is provided for
item, an empty document will be used for the
context.
If returnType is null, then a NullPointerException is thrown.
| | public java.lang.String | evaluate(java.lang.Object item)Evaluate the compiled XPath expression in the specified context and return the result as a String.
This method calls {@link #evaluate(Object item, QName returnType)} with a returnType of
{@link XPathConstants#STRING}.
See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.
If a null value is provided for
item, an empty document will be used for the
context.
| | public java.lang.Object | evaluate(org.xml.sax.InputSource source, javax.xml.namespace.QName returnType)Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as the
specified type.
This method builds a data model for the {@link InputSource} and calls
{@link #evaluate(Object item, QName returnType)} on the resulting document object.
See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.
If returnType is not one of the types defined in {@link XPathConstants},
then an IllegalArgumentException is thrown.
If source or returnType is null,
then a NullPointerException is thrown.
| | public java.lang.String | evaluate(org.xml.sax.InputSource source)Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as a
String.
This method calls {@link #evaluate(InputSource source, QName returnType)} with a returnType of
{@link XPathConstants#STRING}.
See Evaluation of XPath Expressions for context item evaluation,
variable, function and QName resolution and return type conversion.
If source is null, then a NullPointerException is thrown.
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