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package javax.xml.xpath;
import javax.xml.namespace.QName;
import org.xml.sax.InputSource;
XPathExpression
provides access to compiled XPath expressions. The XPath evaluation is affected by the factors described in the following table.
Evaluation of XPath Expressions
Factor
Behavior
context
The type of the context is implementation-dependent. If the value is
null, the operation must have no dependency on the context, otherwise
an XPathExpressionException will be thrown.
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.
Author: Norman Walsh, Jeff Suttor See Also: Since: 1.5
/**
* {@code XPathExpression} provides access to compiled XPath expressions.
* The XPath evaluation is affected by the factors described in the following table.
*
* <a id="XPathExpression-evaluation"></a>
* <table class="striped">
* <caption>Evaluation of XPath Expressions</caption>
* <thead>
* <tr>
* <th scope="col">Factor</th>
* <th scope="col">Behavior</th>
* </tr>
* </thead>
* <tbody>
* <tr>
* <th scope="row">context</th>
* <td>
* The type of the context is implementation-dependent. If the value is
* null, the operation must have no dependency on the context, otherwise
* an XPathExpressionException will be thrown.
*
* For the purposes of evaluating XPath expressions, a DocumentFragment
* is treated like a Document node.
* </td>
* </tr>
* <tr>
* <th scope="row">variables</th>
* <td>
* 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 {@code null} for the variable.
* The value of a variable must be immutable through the course of any single evaluation.
* </td>
* </tr>
* <tr>
* <th scope="row">functions</th>
* <td>
* 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 {@code null} for the function.
* </td>
* </tr>
* <tr>
* <th scope="row">QNames</th>
* <td>
* QNames in the expression are resolved against the XPath namespace context.
* </td>
* </tr>
* <tr>
* <th scope="row">result</th>
* <td>
* 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.
* </td>
* </tr>
* </tbody>
* </table>
*
* <p>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 {@code evaluate}
* method is invoked, applications may not recursively call
* the {@code evaluate} method.
*
* @author Norman Walsh
* @author Jeff Suttor
* @see <a href="http://www.w3.org/TR/xpath#section-Expressions">XML Path Language (XPath) Version 1.0, Expressions</a>
* @since 1.5
*/
public interface XPathExpression {
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.
The parameter item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value is null
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.
Params: - item – The context the XPath expression will be evaluated in.
- returnType – The result type expected to be returned by the XPath expression.
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
.
Implementation Note: The type of the context is usually Node
. Returns: The Object
that is the result of evaluating the expression and converting the result to returnType
.
/**
* Evaluate the compiled XPath expression in the specified context and return the result as the specified type.
*
* <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* <p>
* The parameter {@code item} represents the context the XPath expression
* will be operated on. The type of the context is implementation-dependent.
* If the value is {@code null}, the operation must have no dependency on
* the context, otherwise an XPathExpressionException will be thrown.
*
* @implNote
* The type of the context is usually {@link org.w3c.dom.Node}.
*
* @param item The context the XPath expression will be evaluated in.
* @param returnType The result type expected to be returned by the XPath expression.
*
* @return The {@code Object} that is the result of evaluating the expression and converting the result to
* {@code returnType}.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.
* @throws NullPointerException If {@code returnType} is {@code null}.
*/
public Object evaluate(Object item, QName returnType)
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.
The parameter item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value is null
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.
Params: - item – The context the XPath expression will be evaluated in.
Throws: - XPathExpressionException – If the expression cannot be evaluated.
Implementation Note: The type of the context is usually Node
. Returns: The result of evaluating an XPath expression as a String
.
/**
* Evaluate the compiled XPath expression in the specified context and return the result as a {@code String}.
*
* <p>This method calls {@link #evaluate(Object item, QName returnType)} with a {@code returnType} of
* {@link XPathConstants#STRING}.
*
* <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* <p>
* The parameter {@code item} represents the context the XPath expression
* will be operated on. The type of the context is implementation-dependent.
* If the value is {@code null}, the operation must have no dependency on
* the context, otherwise an XPathExpressionException will be thrown.
*
* @implNote
* The type of the context is usually {@link org.w3c.dom.Node}.
*
* @param item The context the XPath expression will be evaluated in.
*
* @return The result of evaluating an XPath expression as a {@code String}.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
*/
public String evaluate(Object item)
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.
Params: - source – The
InputSource
of the document to evaluate over. - returnType – The desired return type.
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
.
Returns: The Object
that is the result of evaluating the expression and converting the result to returnType
.
/**
* Evaluate the compiled XPath expression in the context
* of the specified {@code InputSource} and return the result as the
* specified type.
*
* <p>This method builds a data model for the {@link InputSource} and calls
* {@link #evaluate(Object item, QName returnType)} on the resulting document object.
*
* <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* <p>If {@code returnType} is not one of the types defined in {@link XPathConstants},
* then an {@code IllegalArgumentException} is thrown.
*
* <p>If {@code source} or {@code returnType} is {@code null},
* then a {@code NullPointerException} is thrown.
*
* @param source The {@code InputSource} of the document to evaluate over.
* @param returnType The desired return type.
*
* @return The {@code Object} that is the result of evaluating the expression and converting the result to
* {@code returnType}.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.
* @throws NullPointerException If {@code source or returnType} is {@code null}.
*/
public 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 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.
Params: - source – The
InputSource
of the document to evaluate over.
Throws: - XPathExpressionException – If the expression cannot be evaluated.
- NullPointerException – If
source
is null
.
Returns: The String
that is the result of evaluating the expression and converting the result to a String
.
/**
* Evaluate the compiled XPath expression in the context
* of the specified {@code InputSource} and return the result as a
* {@code String}.
*
* <p>This method calls {@link #evaluate(InputSource source, QName returnType)} with a {@code returnType} of
* {@link XPathConstants#STRING}.
*
* <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
* variable, function and QName resolution and return type conversion.
*
* <p>If {@code source} is {@code null}, then a {@code NullPointerException} is thrown.
*
* @param source The {@code InputSource} of the document to evaluate over.
*
* @return The {@code String} that is the result of evaluating the expression and converting the result to a
* {@code String}.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws NullPointerException If {@code source} is {@code null}.
*/
public String evaluate(InputSource source)
throws XPathExpressionException;
Evaluate the compiled XPath expression in the specified context, and return the result with the type specified through the class type
. The parameter item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value is null
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.
Params: - item – The context the XPath expression will be evaluated in.
- type – The class type expected to be returned by the XPath expression.
Type parameters: - <T> – The class type that will be returned by the XPath expression.
Throws: - XPathExpressionException – If the expression cannot be evaluated.
- IllegalArgumentException – If
type
is not of the types corresponding to the types defined in the
XPathResultType
, or XPathEvaluationResult is specified as the type but an implementation supporting the ANY
type is not available. - NullPointerException – If
type
is null
.
Implementation Note: The type of the context is usually Node
. Implementation Requirements:
The default implementation in the XPath API is equivalent to:
(T)evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type));
Since the evaluate
method does not support the ANY
type, specifying XPathEvaluationResult as the type will result in IllegalArgumentException. Any implementation supporting the ANY
type must override this method. Returns: The result of evaluating the expression. Since: 9
/**
* Evaluate the compiled XPath expression in the specified context, and return
* the result with the type specified through the {@code class type}.
*
* <p>
* The parameter {@code item} represents the context the XPath expression
* will be operated on. The type of the context is implementation-dependent.
* If the value is {@code null}, the operation must have no dependency on
* the context, otherwise an XPathExpressionException will be thrown.
*
* @implNote
* The type of the context is usually {@link org.w3c.dom.Node}.
*
* @implSpec
* The default implementation in the XPath API is equivalent to:
* <pre> {@code
* (T)evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type));
* }</pre>
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
* XPathEvaluationResult as the type will result in IllegalArgumentException.
* Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
* this method.
*
* @param <T> The class type that will be returned by the XPath expression.
* @param item The context the XPath expression will be evaluated in.
* @param type The class type expected to be returned by the XPath expression.
*
* @return The result of evaluating the expression.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If {@code type} is not of the types
* corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType
* XPathResultType}, or XPathEvaluationResult is specified as the type but an
* implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type is not available.
* @throws NullPointerException If {@code type} is {@code null}.
*
* @since 9
*/
default <T>T evaluateExpression(Object item, Class<T> type)
throws XPathExpressionException
{
return type.cast(evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type)));
}
Evaluate the compiled XPath expression in the specified context. This is equivalent to calling evaluateExpression(Object item, Class<Object> type)
with type XPathEvaluationResult
:
evaluateExpression(item, XPathEvaluationResult.class);
The parameter item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value is null
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.
Params: - item – The context the XPath expression will be evaluated in.
Throws: - XPathExpressionException – If the expression cannot be evaluated.
- IllegalArgumentException – If the implementation of this method does not support the
ANY
type.
Implementation Note: The type of the context is usually Node
. Implementation Requirements:
The default implementation in the XPath API is equivalent to:
evaluateExpression(item, XPathEvaluationResult.class);
Since the evaluate
method does not support the ANY
type, the default implementation of this method will always throw an IllegalArgumentException. Any implementation supporting the ANY
type must therefore override this method. Returns: The result of evaluating the expression. Since: 9
/**
* Evaluate the compiled XPath expression in the specified context. This is
* equivalent to calling {@link #evaluateExpression(Object item, Class type)}
* with type {@link XPathEvaluationResult}:
* <pre> {@code
* evaluateExpression(item, XPathEvaluationResult.class);
* }</pre>
* <p>
* The parameter {@code item} represents the context the XPath expression
* will be operated on. The type of the context is implementation-dependent.
* If the value is {@code null}, the operation must have no dependency on
* the context, otherwise an XPathExpressionException will be thrown.
*
* @implNote
* The type of the context is usually {@link org.w3c.dom.Node}.
*
* @implSpec
* The default implementation in the XPath API is equivalent to:
* <pre> {@code
* evaluateExpression(item, XPathEvaluationResult.class);
* }</pre>
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY}
* type, the default implementation of this method will always throw an
* IllegalArgumentException. Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
* override this method.
*
* @param item The context the XPath expression will be evaluated in.
*
* @return The result of evaluating the expression.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If the implementation of this method
* does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
*
* @since 9
*/
default XPathEvaluationResult<?> evaluateExpression(Object item)
throws XPathExpressionException
{
return evaluateExpression(item, XPathEvaluationResult.class);
}
Evaluate the compiled XPath expression in the specified context, and return the result with the type specified through the class type
This method builds a data model for the InputSource
and calls evaluateExpression(Object item, Class<Object> type)
on the resulting document object.
By default, the JDK's data model is Document
.
Params: - source – The
InputSource
of the document to evaluate over. - type – The class type expected to be returned by the XPath expression.
Type parameters: - <T> – The class type that will be returned by the XPath expression.
Throws: - XPathExpressionException – If the expression cannot be evaluated.
- IllegalArgumentException – If
type
is not of the types corresponding to the types defined in the
XPathResultType
, or XPathEvaluationResult is specified as the type but an implementation supporting the ANY
type is not available. - NullPointerException – If
source or type
is null
.
Implementation Requirements:
The default implementation in the XPath API is equivalent to:
(T)evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type));
Since the evaluate
method does not support the ANY
type, specifying XPathEvaluationResult as the type will result in IllegalArgumentException. Any implementation supporting the ANY
type must override this method. Returns: The result of evaluating the expression. Since: 9
/**
* Evaluate the compiled XPath expression in the specified context,
* and return the result with the type specified through the {@code class type}
* <p>
* This method builds a data model for the {@link InputSource} and calls
* {@link #evaluateExpression(Object item, Class type)} on the resulting
* document object.
* <P>
* By default, the JDK's data model is {@link org.w3c.dom.Document}.
*
* @implSpec
* The default implementation in the XPath API is equivalent to:
* <pre> {@code
(T)evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type));
* }</pre>
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
* XPathEvaluationResult as the type will result in IllegalArgumentException.
* Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
* this method.
*
* @param <T> The class type that will be returned by the XPath expression.
* @param source The {@code InputSource} of the document to evaluate over.
* @param type The class type expected to be returned by the XPath expression.
*
* @return The result of evaluating the expression.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If {@code type} is not of the types
* corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType
* XPathResultType}, or XPathEvaluationResult is specified as the type but an
* implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type
* is not available.
* @throws NullPointerException If {@code source or type} is {@code null}.
*
* @since 9
*/
default <T>T evaluateExpression(InputSource source, Class<T> type)
throws XPathExpressionException
{
return type.cast(evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type)));
}
Evaluate the compiled XPath expression in the specified context. This is equivalent to calling evaluateExpression(InputSource source, Class<Object> type)
with type XPathEvaluationResult
:
evaluateExpression(source, XPathEvaluationResult.class);
Params: - source – The
InputSource
of the document to evaluate over.
Throws: - XPathExpressionException – If the expression cannot be evaluated.
- IllegalArgumentException – If the implementation of this method does not support the
ANY
type. - NullPointerException – If
source
is null
.
Implementation Requirements:
The default implementation in the XPath API is equivalent to:
(XPathEvaluationResult)evaluateExpression(source, XPathEvaluationResult.class);
Since the evaluate
method does not support the ANY
type, the default implementation of this method will always throw an IllegalArgumentException. Any implementation supporting the ANY
type must therefore override this method. Returns: The result of evaluating the expression. Since: 9
/**
* Evaluate the compiled XPath expression in the specified context. This is
* equivalent to calling {@link #evaluateExpression(InputSource source, Class type)}
* with type {@link XPathEvaluationResult}:
* <pre> {@code
* evaluateExpression(source, XPathEvaluationResult.class);
* }</pre>
*
* @implSpec
* The default implementation in the XPath API is equivalent to:
* <pre> {@code
* (XPathEvaluationResult)evaluateExpression(source, XPathEvaluationResult.class);
* }</pre>
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY}
* type, the default implementation of this method will always throw an
* IllegalArgumentException. Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
* override this method.
*
* @param source The {@code InputSource} of the document to evaluate over.
*
* @return The result of evaluating the expression.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If the implementation of this method
* does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
* @throws NullPointerException If {@code source} is {@code null}.
*
* @since 9
*/
default XPathEvaluationResult<?> evaluateExpression(InputSource source)
throws XPathExpressionException
{
return evaluateExpression(source, XPathEvaluationResult.class);
}
}