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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: TransformerFactory.java 884963 2009-11-27 19:11:59Z mrglavas $

package javax.xml.transform;

/**
 * A TransformerFactory instance can be used to create
 * {@link javax.xml.transform.Transformer} and
 * {@link javax.xml.transform.Templates} objects.
 *
 * The system property that determines which Factory implementation
 * to create is named "javax.xml.transform.TransformerFactory".
 * This property names a concrete subclass of the
 * TransformerFactory abstract class. If the property is not
 * defined, a platform default is be used.
 * 
 * @author Jeff Suttor
 */
public abstract class TransformerFactory {
    
    /**
     * Default constructor is protected on purpose.
     */
    protected TransformerFactory() { }


    /**
     * Get current state of canonicalization.
     * 
     * @return current state canonicalization control
     */
    /*
    public boolean getCanonicalization() {
        return canonicalState;
    }
    */
    
    /**
     * Set canonicalization control to true or
     * false.
     * 
     * @param state of canonicalization
     */
    /*
    public void setCanonicalization(boolean state) {
        canonicalState = state;
    }
    */

    /**
     * Obtain a new instance of a TransformerFactory.
     * This static method creates a new factory instance
     * This method uses the following ordered lookup procedure to determine
     * the TransformerFactory implementation class to
     * load:
     * 
     * 
     * Use the javax.xml.transform.TransformerFactory system
     * property.
     * 
     * 
     * Use the properties file "lib/jaxp.properties" in the JRE directory.
     * This configuration file is in standard java.util.Properties
     *  format and contains the fully qualified name of the
     * implementation class with the key being the system property defined
     * above.
     * 
     * The jaxp.properties file is read only once by the JAXP implementation
     * and it's values are then cached for future use.  If the file does not exist
     * when the first attempt is made to read from it, no further attempts are
     * made to check for its existence.  It is not possible to change the value
     * of any property in jaxp.properties after it has been read for the first time.
     * 
     * 
     * Use the Services API (as detailed in the JAR specification), if
     * available, to determine the classname. The Services API will look
     * for a classname in the file
     * META-INF/services/javax.xml.transform.TransformerFactory
     * in jars available to the runtime.
     * 
     * 
     * Platform default TransformerFactory instance.
     * 
     * 
     *
     * Once an application has obtained a reference to a 
     * TransformerFactory it can use the factory to configure
     * and obtain parser instances.
     *
     * @return new TransformerFactory instance, never null.
     *
     * @throws TransformerFactoryConfigurationError Thrown if the implementation
     *    is not available or cannot be instantiated.
     */
    public static TransformerFactory newInstance()
        throws TransformerFactoryConfigurationError {
        try {
            return (TransformerFactory) FactoryFinder.find(
            /* The default property name according to the JAXP spec */
            "javax.xml.transform.TransformerFactory",
            /* The fallback implementation class name */
            "org.apache.xalan.processor.TransformerFactoryImpl");
        } 
        catch (FactoryFinder.ConfigurationError e) {
            throw new TransformerFactoryConfigurationError(e.getException(), e.getMessage());
        }
    }
    
    /**
     * @return new TransformerFactory instance, never null.
     *
     * @throws TransformerFactoryConfigurationError Thrown if the implementation
     *    is not available or cannot be instantiated.
     */
    public static TransformerFactory newInstance(String factoryClassName,
            ClassLoader classLoader) throws TransformerFactoryConfigurationError {
        if (factoryClassName == null) {
            throw new TransformerFactoryConfigurationError("factoryClassName cannot be null.");
        }
        if (classLoader == null) {
            classLoader = SecuritySupport.getContextClassLoader();
        }
        try {
            return (TransformerFactory) FactoryFinder.newInstance(factoryClassName, classLoader, false);
        }
        catch (FactoryFinder.ConfigurationError e) {
            throw new TransformerFactoryConfigurationError(e.getException(), e.getMessage());
        }
    }

    /**
     * Process the Source into a Transformer
     * Object.  The Source is an XSLT document that
     * conforms to 
     * XSL Transformations (XSLT) Version 1.0.  Care must
     * be taken not to use this Transformer in multiple
     * Threads running concurrently.
     * Different TransformerFactories can be used concurrently by
     * different Threads.
     *
     * @param source Source  of XSLT document used to create
     *   Transformer.
     *   Examples of XML Sources include
     *   {@link javax.xml.transform.stream.StreamSource StreamSource},
     *   {@link javax.xml.transform.sax.SAXSource SAXSource},
     *   {@link javax.xml.transform.dom.DOMSource DOMSource} and
     *   {@link javax.xml.transform.stax.StAXSource StAXSource}.
     *
     * @return A Transformer object that may be used to perform
     *   a transformation in a single Thread, never
     *   null.
     *
     * @throws TransformerConfigurationException Thrown if there are errors when
     *    parsing the Source or it is not possible to create a
     *   Transformer instance.
     * 
     * @see 
     *   XSL Transformations (XSLT) Version 1.0
     */
    public abstract Transformer newTransformer(Source source)
        throws TransformerConfigurationException;

    /**
     * Create a new Transformer that performs a copy
     * of the Source to the Result.
     * i.e. the "identity transform".
     *
     * @return A Transformer object that may be used to perform a transformation
     * in a single thread, never null.
     *
     * @exception TransformerConfigurationException Thrown if it is not
     *   possible to create a Transformer instance.
     */
    public abstract Transformer newTransformer()
        throws TransformerConfigurationException;

    /**
     * Process the Source into a Templates object, which is a
     * a compiled representation of the source. This Templates object
     * may then be used concurrently across multiple threads.  Creating
     * a Templates object allows the TransformerFactory to do detailed
     * performance optimization of transformation instructions, without
     * penalizing runtime transformation.
     *
     * @param source An object that holds a URL, input stream, etc.
     *
     * @return A Templates object capable of being used for transformation
     * purposes, never null.
     *
     * @exception TransformerConfigurationException May throw this during the
     * parse when it is constructing the Templates object and fails.
     */
    public abstract Templates newTemplates(Source source)
        throws TransformerConfigurationException;

    /**
     * Get the stylesheet specification(s) associated with the
     * XML Source document via the
     * 
     * xml-stylesheet processing instruction that match the given criteria.
     * Note that it is possible to return several stylesheets, in which case
     * they are applied as if they were a list of imports or cascades in a
     * single stylesheet.
     *
     * @param source The XML source document.
     * @param media The media attribute to be matched.  May be null, in which
     *      case the preferred templates will be used (i.e. alternate = no).
     * @param title The value of the title attribute to match.  May be null.
     * @param charset The value of the charset attribute to match.  May be null.
     *
     * @return A Source Object suitable for passing
     *   to the TransformerFactory.
     * 
     * @throws TransformerConfigurationException An Exception
     *   is thrown if an error occurs during parsing of the
     *   source.
     * 
     * @see 
     *   Associating Style Sheets with XML documents Version 1.0
     */
    public abstract Source getAssociatedStylesheet(
        Source source,
        String media,
        String title,
        String charset)
        throws TransformerConfigurationException;

    /**
     * Set an object that is used by default during the transformation
     * to resolve URIs used in document(), xsl:import, or xsl:include.
     *
     * @param resolver An object that implements the URIResolver interface,
     * or null.
     */
    public abstract void setURIResolver(URIResolver resolver);

    /**
     * Get the object that is used by default during the transformation
     * to resolve URIs used in document(), xsl:import, or xsl:include.
     *
     * @return The URIResolver that was set with setURIResolver.
     */
    public abstract URIResolver getURIResolver();

    //======= CONFIGURATION METHODS =======

	/**
	 * Set a feature for this TransformerFactory and Transformers
	 * or Templates created by this factory.
	 * 
	 * 
	 * Feature names are fully qualified {@link java.net.URI}s.
	 * Implementations may define their own features.
	 * An {@link TransformerConfigurationException} is thrown if this TransformerFactory or the
	 * Transformers or Templates it creates cannot support the feature.
	 * It is possible for an TransformerFactory 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: the implementation will limit XML processing to conform to implementation limits
	 *     and behave in a secure fashion as defined by the implementation.
	 *     Examples include resolving user defined style sheets and functions.
	 *     If XML processing is limited for security reasons, it will be reported via a call to the registered
	 *     {@link ErrorListener#fatalError(TransformerException exception)}.
	 *     See {@link  #setErrorListener(ErrorListener listener)}.
	 *   
	 *   
	 *     false: the implementation will processing XML according to the XML specifications without
	 *     regard to possible implementation limits.
	 *   
	 * 
	 * 
	 * @param name Feature name.
	 * @param value Is feature state true or false.
	 *  
	 * @throws TransformerConfigurationException if this TransformerFactory
	 *   or the Transformers or Templates it creates cannot support this feature.
     * @throws NullPointerException If the name parameter is null.
	 */
	public abstract void setFeature(String name, boolean value)
		throws TransformerConfigurationException;

    /**
     * Look up the value of a feature.
     *
	 * 
	 * Feature names are fully qualified {@link java.net.URI}s.
	 * Implementations may define their own features.
	 * false is returned if this TransformerFactory or the
	 * Transformers or Templates it creates cannot support the feature.
	 * It is possible for an TransformerFactory to expose a feature value but be unable to change its state.
	 * 
	 * 
	 * @param name Feature name.
	 * 
     * @return The current state of the feature, true or false.
     * 
     * @throws NullPointerException If the name parameter is null.
     */
    public abstract boolean getFeature(String name);

    /**
     * Allows the user to set specific attributes on the underlying
     * implementation.  An attribute in this context is defined to
     * be an option that the implementation provides.
     * An IllegalArgumentException is thrown if the underlying
     * implementation doesn't recognize the attribute.
     *
     * @param name The name of the attribute.
     * @param value The value of the attribute.
     */
    public abstract void setAttribute(String name, Object value);

    /**
     * Allows the user to retrieve specific attributes on the underlying
     * implementation.
     * An IllegalArgumentException is thrown if the underlying
     * implementation doesn't recognize the attribute.
     * 
     * @param name The name of the attribute.
     * @return value The value of the attribute.
     */
    public abstract Object getAttribute(String name);

    /**
     * Set the error event listener for the TransformerFactory, which
     * is used for the processing of transformation instructions,
     * and not for the transformation itself.
     * An IllegalArgumentException is thrown if the
     * ErrorListener listener is null.
     *
     * @param listener The new error listener.
     */
    public abstract void setErrorListener(ErrorListener listener);

    /**
     * Get the error event handler for the TransformerFactory.
     *
     * @return The current error handler, which should never be null.
     */
    public abstract ErrorListener getErrorListener();

}