javax.xml.xpath

Class XPathFactory

Contents

  • public abstract class XPathFactory
extends Object

    An XPathFactory instance can be used to create XPath objects.

    See newInstance(String uri) for lookup mechanism.

    The XPathFactory class is not thread-safe. In other words, it is the application's responsibility to ensure that at most one thread is using a XPathFactory object at any given moment. Implementations are encouraged to mark methods as synchronized to protect themselves from broken clients.

    XPathFactory is not re-entrant. While one of the newInstance methods is being invoked, applications may not attempt to recursively invoke a newInstance method, even from the same thread.

    Since:
    1.5

    • Field Detail

      • DEFAULT_PROPERTY_NAME

        public static final String DEFAULT_PROPERTY_NAME

        The default property name according to the JAXP spec.

        See Also:
        Constant Field Values

      • DEFAULT_OBJECT_MODEL_URI

        public static final String DEFAULT_OBJECT_MODEL_URI

        Default Object Model URI.

        See Also:
        Constant Field Values

    • Method Detail

      • newInstance

        public static final XPathFactory newInstance()

        Get a new XPathFactory instance using the default object model, DEFAULT_OBJECT_MODEL_URI, the W3C DOM.

        This method is functionally equivalent to:

           newInstance(DEFAULT_OBJECT_MODEL_URI)

        Since the implementation for the W3C DOM is always available, this method will never fail.

        Returns:
        Instance of an XPathFactory.
        Throws:
        RuntimeException - When there is a failure in creating an XPathFactory for the default object model.

      • newInstance

        public static final XPathFactory newInstance(String uri)
                                      throws XPathFactoryConfigurationException

        Get a new XPathFactory instance using the specified object model.

        To find a XPathFactory object, this method looks the following places in the following order where "the class loader" refers to the context class loader:

        1. If the system property DEFAULT_PROPERTY_NAME + ":uri" is present, where uri is the parameter to this method, then its value is read as a class name. The method will try to create a new instance of this class by using the class loader, and returns it if it is successfully created.
        2. ${java.home}/lib/jaxp.properties is read and the value associated with the key being the system property above is looked for. If present, the value is processed just like above.
        3. The class loader is asked for service provider provider-configuration files matching javax.xml.xpath.XPathFactory in the resource directory META-INF/services. See the JAR File Specification for file format and parsing rules. Each potential service provider is required to implement the method: 
                 isObjectModelSupported(String objectModel)
          The first service provider found in class loader order that supports the specified object model is returned.
        4. Platform default XPathFactory is located in a platform specific way. There must be a platform default XPathFactory for the W3C DOM, i.e. DEFAULT_OBJECT_MODEL_URI.

        If everything fails, an XPathFactoryConfigurationException will be thrown.

        Tip for Trouble-shooting:

        See Properties.load(java.io.InputStream) for exactly how a property file is parsed. In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it. For example:

           http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
        Parameters:
        uri - Identifies the underlying object model. The specification only defines the URI DEFAULT_OBJECT_MODEL_URI, http://java.sun.com/jaxp/xpath/dom for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
        Returns:
        Instance of an XPathFactory.
        Throws:
        XPathFactoryConfigurationException - If the specified object model is unavailable.
        NullPointerException - If uri is null.
        IllegalArgumentException - If uri is null or uri.length() == 0.

      • newInstance

        public static XPathFactory newInstance(String uri,
                       String factoryClassName,
                       ClassLoader classLoader)
                                throws XPathFactoryConfigurationException

        Obtain a new instance of a XPathFactory from a factory class name. XPathFactory is returned if specified factory class supports the specified object model. This function is useful when there are multiple providers in the classpath. It gives more control to the application as it can specify which provider should be loaded.

        Tip for Trouble-shooting

        Setting the jaxp.debug system property will cause this method to print a lot of debug messages to System.err about what it is doing and where it is looking at.

        If you have problems try:

         java -Djaxp.debug=1 YourProgram ....
        Parameters:
        uri - Identifies the underlying object model. The specification only defines the URI DEFAULT_OBJECT_MODEL_URI,http://java.sun.com/jaxp/xpath/dom for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
        factoryClassName - fully qualified factory class name that provides implementation of javax.xml.xpath.XPathFactory.
        classLoader - ClassLoader used to load the factory class. If null current Thread's context classLoader is used to load the factory class.
        Returns:
        New instance of a XPathFactory
        Throws:
        XPathFactoryConfigurationException - if factoryClassName is null, or the factory class cannot be loaded, instantiated or the factory class does not support the object model specified in the uri parameter.
        NullPointerException - If uri is null.
        IllegalArgumentException - If uri is null or uri.length() == 0.
        Since:
        1.6
        See Also:
        newInstance(), newInstance(String uri)

      • isObjectModelSupported

        public abstract boolean isObjectModelSupported(String objectModel)

        Is specified object model supported by this XPathFactory?

        Parameters:
        objectModel - Specifies the object model which the returned XPathFactory will understand.
        Returns:
        true if XPathFactory supports objectModel, else false.
        Throws:
        NullPointerException - If objectModel is null.
        IllegalArgumentException - If objectModel.length() == 0.

      • getFeature

        public abstract boolean getFeature(String name)
                            throws XPathFactoryConfigurationException

        Get the state of the named feature.

        Feature names are fully qualified URIs. Implementations may define their own features. An XPathFactoryConfigurationException is thrown if this XPathFactory or the XPaths it creates cannot support the feature. It is possible for an XPathFactory to expose a feature value but be unable to change its state.

        Parameters:
        name - Feature name.
        Returns:
        State of the named feature.
        Throws:
        XPathFactoryConfigurationException - if this XPathFactory or the XPaths it creates cannot support this feature.
        NullPointerException - if name is null.

      • setXPathVariableResolver

        public abstract void setXPathVariableResolver(XPathVariableResolver resolver)

        Establish a default variable resolver.

        Any XPath objects constructed from this factory will use the specified resolver by default.

        A NullPointerException is thrown if resolver is null.

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

      • setXPathFunctionResolver

        public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver)

        Establish a default function resolver.

        Any XPath objects constructed from this factory will use the specified resolver by default.

        A NullPointerException is thrown if resolver is null.

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

      • newXPath

        public abstract XPath newXPath()

        Return a new XPath using the underlying object model determined when the XPathFactory was instantiated.

        Returns:
        New instance of an XPath.

Document created the 11/06/2005, last modified the 04/03/2020
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