public 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. |
variables | If the expression contains a variable reference, its value will be found through the XPathVariableResolver . An 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 XPathFunctionResolver . An 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 XPathConstants . Conversion to the return type follows XPath conversion rules. |
An XPath expression is not thread-safe and not reentrant. In other words, it is the application's responsibility to make sure that one 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.
Object evaluate(Object item, QName returnType) throws XPathExpressionException
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 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.
item
- The starting context (a node, for example).returnType
- The desired return type.Object
that is the result of evaluating the expression and converting the result to returnType
.XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If returnType
is not one of the types defined in XPathConstants
.NullPointerException
- If returnType
is null
.String evaluate(Object item) throws XPathExpressionException
Evaluate the compiled XPath expression in the specified context and return the result as a String
.
This method calls evaluate(Object item, QName returnType)
with a returnType
of 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.
item
- The starting context (a node, for example).String
that is the result of evaluating the expression and converting the result to a String
.XPathExpressionException
- If the expression cannot be evaluated.Object evaluate(InputSource source, QName returnType) throws XPathExpressionException
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 InputSource
and calls 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 XPathConstants
, then an IllegalArgumentException
is thrown.
If source
or returnType
is null
, then a NullPointerException
is thrown.
source
- The InputSource
of the document to evaluate over.returnType
- The desired return type.Object
that is the result of evaluating the expression and converting the result to returnType
.XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If returnType
is not one of the types defined in XPathConstants
.NullPointerException
- If source
or returnType
is null
.String evaluate(InputSource source) throws XPathExpressionException
Evaluate the compiled XPath expression in the context of the specified InputSource
and return the result as a String
.
This method calls evaluate(InputSource source, QName returnType)
with a returnType
of 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.
source
- The InputSource
of the document to evaluate over.String
that is the result of evaluating the expression and converting the result to a String
.XPathExpressionException
- If the expression cannot be evaluated.NullPointerException
- If source
is null
.
© 1993–2017, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.