// $Id: XPathFactory.java,v 1.13.10.1.2.1 2004/09/16 09:25:15 nb131165 Exp $
/*
* @(#)XPathFactory.java 1.10 05/01/04
*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.xml.xpath;
/**
* <p>An <code>XPathFactory</code> instance can be used to create
* {@link javax.xml.xpath.XPath} objects.</p>
*
*<p>See {@link #newInstance(String uri)} for lookup mechanism.</p>
*
* @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
* @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
* @version $Revision: 1.13.10.1.2.1 $, $Date: 2004/09/16 09:25:15 $
* @since 1.5
*/
public abstract class XPathFactory {
/**
* <p>The default property name according to the JAXP spec.</p>
*/
public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory";
/**
* <p>Default Object Model URI.</p>
*/
public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom";
/**
*<p> Take care of restrictions imposed by java security model </p>
*/
private static SecuritySupport ss = new SecuritySupport() ;
/**
* <p>Protected constructor as {@link #newInstance()} or {@link #newInstance(String uri)}
* should be used to create a new instance of an <code>XPathFactory</code>.</p>
*/
protected XPathFactory() {
}
/**
* <p>Get a new <code>XPathFactory</code> instance using the default object model,
* {@link #DEFAULT_OBJECT_MODEL_URI},
* the W3C DOM.</p>
*
* <p>This method is functionally equivalent to:</p>
* <pre>
* newInstance(DEFAULT_OBJECT_MODEL_URI)
* </pre>
*
* <p>Since the implementation for the W3C DOM is always available, this method will never fail.</p>
*
* @return Instance of an <code>XPathFactory</code>.
*/
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()
);
}
}
/**
* <p>Get a new <code>XPathFactory</code> instance using the specified object model.</p>
*
* <p>To find a <code>XPathFactory</code> object,
* this method looks the following places in the following order where "the class loader" refers to the context class loader:</p>
* <ol>
* <li>
* 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.
* </li>
* <li>
* ${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.
* </li>
* <li>
* The class loader is asked for service provider provider-configuration files matching <code>javax.xml.xpath.XPathFactory</code>
* 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:
* <pre>
* {@link #isObjectModelSupported(String objectModel)}
* </pre>
* The first service provider found in class loader order that supports the specified object model is returned.
* </li>
* <li>
* Platform default <code>XPathFactory</code> 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}.
* </li>
* </ol>
* <p>If everything fails, an <code>XPathFactoryConfigurationException</code> will be thrown.</p>
*
* <p>Tip for Trouble-shooting:</p>
* <p>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:</p>
* <pre>
* http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
* </pre>
*
* @param uri Identifies the underlying object model.
* The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI},
* <code>http://java.sun.com/jaxp/xpath/dom</code> 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 <code>XPathFactory</code>.
*
* @throws XPathFactoryConfigurationException If the specified object model is unavailable.
* @throws NullPointerException If <code>uri</code> is <code>null</code>.
* @throws IllegalArgumentException If <code>uri.length() == 0</code>.
*/
public static final XPathFactory newInstance(final String uri)
throws XPathFactoryConfigurationException {
if (uri == null) {
throw new NullPointerException(
"XPathFactory#newInstance(String uri) cannot be called with uri == null"
);
}
if (uri.length() == 0) {
throw new IllegalArgumentException(
"XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
);
}
ClassLoader classLoader = ss.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 XPathFctory implementation found for the object model: "
+ uri
);
}
return xpathFactory;
}
/**
* <p>Is specified object model supported by this <code>XPathFactory</code>?</p>
*
* @param objectModel Specifies the object model which the returned <code>XPathFactory</code> will understand.
*
* @return <code>true</code> if <code>XPathFactory</code> supports <code>objectModel</code>, else <code>false</code>.
*
* @throws NullPointerException If <code>objectModel</code> is <code>null</code>.
* @throws IllegalArgumentException If <code>objectModel.length() == 0</code>.
*/
public abstract boolean isObjectModelSupported(String objectModel);
/**
* <p>Set a feature for this <code>XPathFactory</code> and <code>XPath</code>s created by this factory.</p>
*
* <p>
* Feature names are fully qualified {@link java.net.URI}s.
* Implementations may define their own features.
* An {@link XPathFactoryConfigurationException} is thrown if this <code>XPathFactory</code> or the <code>XPath</code>s
* it creates cannot support the feature.
* It is possible for an <code>XPathFactory</code> to expose a feature value but be unable to change its state.
* </p>
*
* <p>
* All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature.
* When the feature is <code>true</code>, 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}.
* </p>
*
* @param name Feature name.
* @param value Is feature state <code>true</code> or <code>false</code>.
*
* @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s
* it creates cannot support this feature.
* @throws NullPointerException if <code>name</code> is <code>null</code>.
*/
public abstract void setFeature(String name, boolean value)
throws XPathFactoryConfigurationException;
/**
* <p>Get the state of the named feature.</p>
*
* <p>
* Feature names are fully qualified {@link java.net.URI}s.
* Implementations may define their own features.
* An {@link XPathFactoryConfigurationException} is thrown if this <code>XPathFactory</code> or the <code>XPath</code>s
* it creates cannot support the feature.
* It is possible for an <code>XPathFactory</code> to expose a feature value but be unable to change its state.
* </p>
*
* @param name Feature name.
*
* @return State of the named feature.
*
* @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s
* it creates cannot support this feature.
* @throws NullPointerException if <code>name</code> is <code>null</code>.
*/
public abstract boolean getFeature(String name)
throws XPathFactoryConfigurationException;
/**
* <p>Establish a default variable resolver.</p>
*
* <p>Any <code>XPath</code> objects constructed from this factory will use
* the specified resolver by default.</p>
*
* <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
*
* @param resolver Variable resolver.
*
* @throws NullPointerException If <code>resolver</code> is <code>null</code>.
*/
public abstract void setXPathVariableResolver(XPathVariableResolver resolver);
/**
* <p>Establish a default function resolver.</p>
*
* <p>Any <code>XPath</code> objects constructed from this factory will use
* the specified resolver by default.</p>
*
* <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
*
* @param resolver XPath function resolver.
*
* @throws NullPointerException If <code>resolver</code> is <code>null</code>.
*/
public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver);
/**
* <p>Return a new <code>XPath</code> using the underlying object
* model determined when the <code>XPathFactory</code> was instantiated.</p>
*
* @return New instance of an <code>XPath</code>.
*/
public abstract XPath newXPath();
}
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