Module java.xml
Package javax.xml.xpath

Interface XPathExpression


  • public interface XPathExpression
    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.

    Since:
    1.5
    See Also:
    XML Path Language (XPath) Version 1.0, Expressions

    • Method Detail

      • evaluate

        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.

        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.

        Implementation Note:
        The type of the context is usually Node.
        Parameters:
        item - The context the XPath expression will be evaluated in.
        returnType - The result type expected to be returned by the XPath expression.
        Returns:
        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.

      • evaluate

        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.

        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.

        Implementation Note:
        The type of the context is usually Node.
        Parameters:
        item - The context the XPath expression will be evaluated in.
        Returns:
        The result of evaluating an XPath expression as a String.
        Throws:
        XPathExpressionException - If the expression cannot be evaluated.

      • evaluate

        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.

        Parameters:
        source - The InputSource of the document to evaluate over.
        returnType - The desired return type.
        Returns:
        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.

      • evaluateExpression

        default <T> T evaluateExpression​(Object item,
                                 Class<T> type)
                          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.

        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.
        Implementation Note:
        The type of the context is usually Node.
        Type Parameters:
        T - The class type that will be returned by the XPath expression.
        Parameters:
        item - The context the XPath expression will be evaluated in.
        type - The class type expected to be returned by the XPath expression.
        Returns:
        The result of evaluating the 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.
        Since:
        9

      • evaluateExpression

        default XPathEvaluationResult<?> evaluateExpression​(Object item)
                                             throws XPathExpressionException
        Evaluate the compiled XPath expression in the specified context. This is equivalent to calling evaluateExpression(Object item, Class 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.

        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.
        Implementation Note:
        The type of the context is usually Node.
        Parameters:
        item - The context the XPath expression will be evaluated in.
        Returns:
        The result of evaluating the expression.
        Throws:
        XPathExpressionException - If the expression cannot be evaluated.
        IllegalArgumentException - If the implementation of this method does not support the ANY type.
        Since:
        9

      • evaluateExpression

        default <T> T evaluateExpression​(InputSource source,
                                 Class<T> type)
                          throws XPathExpressionException
        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 type) on the resulting document object.

        By default, the JDK's data model is Document.

        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.
        Type Parameters:
        T - The class type that will be returned by the XPath expression.
        Parameters:
        source - The InputSource of the document to evaluate over.
        type - The class type expected to be returned by the XPath expression.
        Returns:
        The result of evaluating the 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.
        Since:
        9

      • evaluateExpression

        default XPathEvaluationResult<?> evaluateExpression​(InputSource source)
                                             throws XPathExpressionException
        Evaluate the compiled XPath expression in the specified context. This is equivalent to calling evaluateExpression(InputSource source, Class type) with type XPathEvaluationResult: 
         
     evaluateExpression(source, XPathEvaluationResult.class);
        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.
        Parameters:
        source - The InputSource of the document to evaluate over.
        Returns:
        The result of evaluating the expression.
        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.
        Since:
        9