Module java.xml
Package javax.xml.xpath

Interface XPath

public interface XPath
XPath provides access to the XPath evaluation environment and 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 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.

An XPath object is not thread-safe and not reentrant. In other words, it is the application's responsibility to make sure that one XPath 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

  • Method Details

    • reset

      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 XPaths thus saving resources associated with the creation of new XPaths.

      The reset XPath is not guaranteed to have the same XPathFunctionResolver, XPathVariableResolver or NamespaceContext Objects, e.g. Object.equals(Object obj). It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver and NamespaceContext.

    • setXPathVariableResolver

      void setXPathVariableResolver​(XPathVariableResolver resolver)
      Establish a variable resolver.

      A NullPointerException is thrown if resolver is null.

      Parameters:
      resolver - Variable resolver.
      Throws:
      NullPointerException - If resolver is null.

    • getXPathVariableResolver

      XPathVariableResolver getXPathVariableResolver()
      Return the current variable resolver.

      null is returned in no variable resolver is in effect.

      Returns:
      Current variable resolver.

    • setXPathFunctionResolver

      void setXPathFunctionResolver​(XPathFunctionResolver resolver)
      Establish a function resolver.

      A NullPointerException is thrown if resolver is null.

      Parameters:
      resolver - XPath function resolver.
      Throws:
      NullPointerException - If resolver is null.

    • getXPathFunctionResolver

      XPathFunctionResolver getXPathFunctionResolver()
      Return the current function resolver.

      null is returned in no function resolver is in effect.

      Returns:
      Current function resolver.

    • setNamespaceContext

      void setNamespaceContext​(NamespaceContext nsContext)
      Establish a namespace context.

      A NullPointerException is thrown if nsContext is null.

      Parameters:
      nsContext - Namespace context to use.
      Throws:
      NullPointerException - If nsContext is null.

    • getNamespaceContext

      NamespaceContext getNamespaceContext()
      Return the current namespace context.

      null is returned in no namespace context is in effect.

      Returns:
      Current Namespace context.

    • compile

      XPathExpression compile​(String expression) throws XPathExpressionException
      Compile an XPath expression for later evaluation.

      If expression contains any XPathFunctions, they must be available via the XPathFunctionResolver. An XPathExpressionException will be thrown if the XPathFunction cannot be resovled with the XPathFunctionResolver.

      If expression contains any variables, the XPathVariableResolver in effect at compile time will be used to resolve them.

      Parameters:
      expression - The XPath expression.
      Returns:
      Compiled XPath expression.
      Throws:
      XPathExpressionException - If expression cannot be compiled.
      NullPointerException - If expression is null.

    • evaluate

      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.

      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:
      expression - The XPath expression.
      item - The context the XPath expression will be evaluated in.
      returnType - The result type expected to be returned by the XPath expression.
      Returns:
      The result of evaluating an XPath expression as an Object of returnType.
      Throws:
      XPathExpressionException - If expression cannot be evaluated.
      IllegalArgumentException - If returnType is not one of the types defined in XPathConstants ( NUMBER, STRING, BOOLEAN, NODE or NODESET).
      NullPointerException - If expression or returnType is null.

    • evaluate

      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.

      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:
      expression - The XPath expression.
      item - The context the XPath expression will be evaluated in.
      Returns:
      The result of evaluating an XPath expression as a String.
      Throws:
      XPathExpressionException - If expression cannot be evaluated.
      NullPointerException - If expression is null.

    • evaluate

      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.

      Parameters:
      expression - The XPath expression.
      source - The input source of the document to evaluate over.
      returnType - The desired return type.
      Returns:
      The Object that encapsulates the result of evaluating the expression.
      Throws:
      XPathExpressionException - If expression cannot be evaluated.
      IllegalArgumentException - If returnType is not one of the types defined in XPathConstants.
      NullPointerException - If expression, source or returnType is null.

    • evaluate

      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.

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

    • evaluateExpression

      default <T> T evaluateExpression​(String expression, Object item, Class<T> type) throws XPathExpressionException
      Evaluate an 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(expression, 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:
      expression - The XPath expression.
      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 XPathEvaluationResult.XPathResultType, or XPathEvaluationResult is specified as the type but an implementation supporting the ANY type is not available.
      NullPointerException - If expression or type is null.
      Since:
      9

    • evaluateExpression

      default XPathEvaluationResult<?> evaluateExpression​(String expression, Object item) throws XPathExpressionException
      Evaluate an XPath expression in the specified context. This is equivalent to calling evaluateExpression(String expression, Object item, Class type) with type XPathEvaluationResult: 
       
     evaluateExpression(expression, 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(expression, 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:
      expression - The XPath expression.
      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.
      NullPointerException - If expression is null.
      Since:
      9

    • evaluateExpression

      default <T> T evaluateExpression​(String expression, InputSource source, Class<T> type) throws XPathExpressionException
      Evaluate an XPath expression in the context of the specified source and return the result as specified.

      This method builds a data model for the InputSource and calls evaluateExpression(String expression, Object item, Class type) on the resulting document object. The data model is usually Document

      Implementation Requirements:
      The default implementation in the XPath API is equivalent to: 
       
           (T)evaluate(expression, 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:
      expression - The XPath expression.
      source - The input source 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 expression, source or typeis null.
      Since:
      9

    • evaluateExpression

      default XPathEvaluationResult<?> evaluateExpression​(String expression, InputSource source) throws XPathExpressionException
      Evaluate an XPath expression in the specified context. This is equivalent to calling evaluateExpression(String expression, Object item, Class type) with type XPathEvaluationResult: 
       
     evaluateExpression(expression, item, XPathEvaluationResult.class);
      Implementation Requirements:
      The default implementation in the XPath API is equivalent to: 
       
     evaluateExpression(expression, 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:
      expression - The XPath expression.
      source - The input source 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 expression or source is null.
      Since:
      9