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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// $Id: XPathFactory.java 888889 2009-12-09 17:43:18Z mrglavas $
package javax.xml.xpath;
/**
* An XPathFactory instance can be used to create
* {@link javax.xml.xpath.XPath} objects.
*
*See {@link #newInstance(String uri)} for lookup mechanism.
*
* @author Norman Walsh
* @author Jeff Suttor
* @version $Revision: 888889 $, $Date: 2009-12-09 09:43:18 -0800 (Wed, 09 Dec 2009) $
* @since 1.5
*/
public abstract class XPathFactory {
/**
* The default property name according to the JAXP spec.
*/
public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory";
/**
* Default Object Model URI.
*/
public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom";
/**
* Protected constructor as {@link #newInstance()}, {@link #newInstance(String uri)}
* or {@link #newInstance(String uri, String factoryClassName, ClassLoader classLoader)}
* should be used to create a new instance of an XPathFactory.
*/
protected XPathFactory() {
}
/**
* Get a new XPathFactory instance using the default object model,
* {@link #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.
*
* @return Instance of an XPathFactory.
*/
public static final XPathFactory newInstance() {
try {
return newInstance(DEFAULT_OBJECT_MODEL_URI);
}
catch (XPathFactoryConfigurationException xpathFactoryConfigurationException) {
throw new RuntimeException(
"XPathFactory#newInstance() failed to create an XPathFactory for the default object model: "
+ DEFAULT_OBJECT_MODEL_URI
+ " with the XPathFactoryConfigurationException: "
+ xpathFactoryConfigurationException.toString()
);
}
}
/**
* 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:
*
* -
* If the system property {@link #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.
*
* -
* ${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.
*
* -
* 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:
*
* {@link #isObjectModelSupported(String objectModel)}
*
* The first service provider found in class loader order that supports the specified object model is returned.
*
* -
* Platform default
XPathFactory is located in a platform specific way.
* There must be a platform default XPathFactory for the W3C DOM, i.e. {@link #DEFAULT_OBJECT_MODEL_URI}.
*
*
* If everything fails, an XPathFactoryConfigurationException will be thrown.
*
* Tip for Trouble-shooting:
* See {@link java.util.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
*
*
* @param uri Identifies the underlying object model.
* The specification only defines the URI {@link #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.
*
* @return Instance of an XPathFactory.
*
* @throws XPathFactoryConfigurationException If the specified object model is unavailable.
* @throws NullPointerException If uri is null.
* @throws IllegalArgumentException If uri.length() == 0.
*/
public static final XPathFactory newInstance(final String uri)
throws XPathFactoryConfigurationException {
if (uri == null) {
throw new NullPointerException("uri == null");
}
if (uri.length() == 0) {
throw new IllegalArgumentException(
"XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
);
}
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader == null) {
//use the current class loader
classLoader = XPathFactory.class.getClassLoader();
}
XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri);
if (xpathFactory == null) {
throw new XPathFactoryConfigurationException(
"No XPathFactory implementation found for the object model: "
+ uri
);
}
return xpathFactory;
}
/**
* @return Instance of an XPathFactory.
*
* @throws XPathFactoryConfigurationException If the specified object model is unavailable.
* @throws NullPointerException If uri is null.
* @throws IllegalArgumentException If uri.length() == 0.
*/
public static XPathFactory newInstance(String uri, String factoryClassName,
ClassLoader classLoader) throws XPathFactoryConfigurationException {
if (uri == null) {
throw new NullPointerException("uri == null");
}
if (uri.length() == 0) {
throw new IllegalArgumentException(
"XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
);
}
if (factoryClassName == null) {
throw new XPathFactoryConfigurationException("factoryClassName cannot be null.");
}
if (classLoader == null) {
classLoader = Thread.currentThread().getContextClassLoader();
}
XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).createInstance(factoryClassName);
if (xpathFactory == null || !xpathFactory.isObjectModelSupported(uri)) {
throw new XPathFactoryConfigurationException(
"No XPathFactory implementation found for the object model: "
+ uri
);
}
return xpathFactory;
}
/**
* Is specified object model supported by this XPathFactory?
*
* @param objectModel Specifies the object model which the returned XPathFactory will understand.
*
* @return true if XPathFactory supports objectModel, else false.
*
* @throws NullPointerException If objectModel is null.
* @throws IllegalArgumentException If objectModel.length() == 0.
*/
public abstract boolean isObjectModelSupported(String objectModel);
/**
* Set a feature for this XPathFactory and XPaths created by this factory.
*
*
* Feature names are fully qualified {@link java.net.URI}s.
* Implementations may define their own features.
* An {@link 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.
*
*
*
* All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature.
* When the feature is true, any reference to an external function is an error.
* Under these conditions, the implementation must not call the {@link XPathFunctionResolver}
* and must throw an {@link XPathFunctionException}.
*
*
* @param name Feature name.
* @param value Is feature state true or false.
*
* @throws XPathFactoryConfigurationException if this XPathFactory or the XPaths
* it creates cannot support this feature.
* @throws NullPointerException if name is null.
*/
public abstract void setFeature(String name, boolean value)
throws XPathFactoryConfigurationException;
/**
* Get the state of the named feature.
*
*
* Feature names are fully qualified {@link java.net.URI}s.
* Implementations may define their own features.
* An {@link 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.
*
*
* @param name Feature name.
*
* @return State of the named feature.
*
* @throws XPathFactoryConfigurationException if this XPathFactory or the XPaths
* it creates cannot support this feature.
* @throws NullPointerException if name is null.
*/
public abstract boolean getFeature(String name)
throws XPathFactoryConfigurationException;
/**
* 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.
*
* @param resolver Variable resolver.
*
* @throws NullPointerException If resolver is null.
*/
public abstract void setXPathVariableResolver(XPathVariableResolver 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.
*
* @param resolver XPath function resolver.
*
* @throws NullPointerException If resolver is null.
*/
public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver);
/**
* Return a new XPath using the underlying object
* model determined when the XPathFactory was instantiated.
*
* @return New instance of an XPath.
*/
public abstract XPath newXPath();
}