javax.xml.xpath
Interface XPath
XPath
provides access to the XPath evaluation environment and 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
set with setXPathVariableResolver(XPathVariableResolver resolver) .
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
set with setXPathFunctionResolver(XPathFunctionResolver resolver) .
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
set with setNamespaceContext(NamespaceContext nsContext) .
|
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.
|
$Revision: 226183 $, $Date: 2005-04-08 12:39:14 +0200 (Fri, 08 Apr 2005) $
evaluate
public String evaluate(String expression,
Object item)
throws XPathExpressionException
Evaluate an XPath expression in the specified context and return the result as a
String
.
This method calls
evaluate(String expression, 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.
If
expression
is
null
, then a
NullPointerException
is thrown.
expression
- The XPath expression.item
- The starting context (node or node list, for example).
- The
String
that is the result of evaluating the expression and
converting the result to a String
.
evaluate
public Object evaluate(String expression,
Object item,
QName returnType)
throws XPathExpressionException
Evaluate an
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
(
NUMBER
,
STRING
,
BOOLEAN
,
NODE
or
NODESET
)
then an
IllegalArgumentException
is thrown.
If a
null
value is provided for
item
, an empty document will be used for the
context.
If
expression
or
returnType
is
null
, then a
NullPointerException
is thrown.
expression
- The XPath expression.item
- The starting context (node or node list, for example).returnType
- The desired return type.
- Result of evaluating an XPath expression as an
Object
of returnType
.
evaluate
public String evaluate(String expression,
InputSource source)
throws XPathExpressionException
Evaluate an XPath expression in the context of the specified
InputSource
and return the result as a
String
.
This method calls
evaluate(String expression, 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
expression
or
source
is
null
,
then a
NullPointerException
is thrown.
expression
- The XPath expression.source
- The InputSource
of the document to evaluate over.
- The
String
that is the result of evaluating the expression and
converting the result to a String
.
evaluate
public Object evaluate(String expression,
InputSource source,
QName returnType)
throws XPathExpressionException
Evaluate an 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(String expression, 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
expression
,
source
or
returnType
is
null
,
then a
NullPointerException
is thrown.
expression
- The XPath expression.source
- The input source of the document to evaluate over.returnType
- The desired return type.
- The
Object
that encapsulates the result of evaluating the expression.
getNamespaceContext
public NamespaceContext getNamespaceContext()
Return the current namespace context.
null
is returned in no namespace context is in effect.
- Current Namespace context.
getXPathFunctionResolver
public XPathFunctionResolver getXPathFunctionResolver()
Return the current function resolver.
null
is returned in no function resolver is in effect.
- Current function resolver.
getXPathVariableResolver
public XPathVariableResolver getXPathVariableResolver()
Return the current variable resolver.
null
is returned in no variable resolver is in effect.
- Current variable resolver.
reset
public void reset()
Reset this
XPath
to its original configuration.
XPath
is reset to the same state as when it was created with
XPathFactory.newXPath()
.
reset()
is designed to allow the reuse of existing
XPath
s
thus saving resources associated with the creation of new
XPath
s.
The reset
XPath
is not guaranteed to have the same
XPathFunctionResolver
,
XPathVariableResolver
or
NamespaceContext
Object
s, e.g.
Object.equals(Object obj)
.
It is guaranteed to have a functionally equal
XPathFunctionResolver
,
XPathVariableResolver
and
NamespaceContext
.
setNamespaceContext
public void setNamespaceContext(NamespaceContext nsContext)
Establish a namespace context.
A
NullPointerException
is thrown if
nsContext
is
null
.
nsContext
- Namespace context to use.
setXPathFunctionResolver
public void setXPathFunctionResolver(XPathFunctionResolver resolver)
Establish a function resolver.
A
NullPointerException
is thrown if
resolver
is
null
.
resolver
- XPath function resolver.
setXPathVariableResolver
public void setXPathVariableResolver(XPathVariableResolver resolver)
Establish a variable resolver.
A
NullPointerException
is thrown if
resolver
is
null
.
resolver
- Variable resolver.