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Added in API level 8

XPathExpression

public interface XPathExpression

javax.xml.xpath.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.

See also:

Summary

Public methods

abstract String evaluate(Object item)

Evaluate the compiled XPath expression in the specified context and return the result as a String.

abstract String evaluate(InputSource source)

Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as a String.

abstract Object evaluate(InputSource source, QName returnType)

Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as the specified type.

abstract Object evaluate(Object item, QName returnType)

Evaluate the compiled XPath expression in the specified context and return the result as the specified type.

Public methods

evaluate

Added in API level 8
String evaluate (Object item)

Evaluate the compiled XPath expression in the specified context and return the result as a String.

This method calls evaluate(Object, QName) with a returnType of 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.

Parameters
item Object: The starting context (node or node list, for example).
Returns
String The String that is the result of evaluating the expression and converting the result to a String.
Throws
XPathExpressionException If the expression cannot be evaluated.

evaluate

Added in API level 8
String evaluate (InputSource source)

Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as a String.

This method calls evaluate(InputSource, QName) with a returnType of 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.

Parameters
source InputSource: The InputSource of the document to evaluate over.
Returns
String The String that is the result of evaluating the expression and converting the result to a String.
Throws
XPathExpressionException If the expression cannot be evaluated.
NullPointerException If source is null.

evaluate

Added in API level 8
Object evaluate (InputSource source, 
                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 InputSource and calls evaluate(Object, QName) 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.

Parameters
source InputSource: The InputSource of the document to evaluate over.
returnType QName: The desired return type.
Returns
Object The Object that is the result of evaluating the expression and converting the result to returnType.
Throws
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.

evaluate

Added in API level 8
Object evaluate (Object item, 
                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 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.

Parameters
item Object: The starting context (node or node list, for example).
returnType QName: The desired return type.
Returns
Object The Object that is the result of evaluating the expression and converting the result to returnType.
Throws
XPathExpressionException If the expression cannot be evaluated.
IllegalArgumentException If returnType is not one of the types defined in XPathConstants.
NullPointerException If returnType is null.
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