code: /*
   * 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.
   */
  /*
   * $Id$
   */
  package org.apache.xml.serializer;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.Writer;
  import java.util.Properties;
  
  import org.xml.sax.ContentHandler;
  
  /**
   * The Serializer interface is implemented by a serializer to enable users to:
   * <ul>
   * <li>get and set streams or writers
   * <li>configure the serializer with key/value properties
   * <li>get an org.xml.sax.ContentHandler or a DOMSerializer to provide input to
   * </ul>
   *
   * <p>
   * Here is an example using the asContentHandler() method:
   * <pre>
   * java.util.Properties props = 
   *   OutputPropertiesFactory.getDefaultMethodProperties(Method.TEXT);
   * Serializer ser = SerializerFactory.getSerializer(props);
   * java.io.PrintStream ostream = System.out; 
   * ser.setOutputStream(ostream);
   * 
   * // Provide the SAX input events
   * ContentHandler handler = ser.asContentHandler();
   * handler.startDocument();
   * char[] chars = { 'a', 'b', 'c' };
   * handler.characters(chars, 0, chars.length);
   * handler.endDocument();
   * 
   * ser.reset(); // get ready to use the serializer for another document
   *              // of the same output method (TEXT).
   * </pre>
   * 
   * <p>
   * As an alternate to supplying a series of SAX events as input through the 
   * ContentHandler interface, the input to serialize may be given as a DOM. 
   * <p>
   * For example:
   * <pre>
   * org.w3c.dom.Document     inputDoc;
   * org.apache.xml.serializer.Serializer   ser;
   * java.io.Writer owriter;
   * 
   * java.util.Properties props = 
   *   OutputPropertiesFactory.getDefaultMethodProperties(Method.XML);
   * Serializer ser = SerializerFactory.getSerializer(props);
   * owriter = ...;  // create a writer to serialize the document to
   * ser.setWriter( owriter );
   * 
   * inputDoc = ...; // create the DOM document to be serialized
   * DOMSerializer dser = ser.asDOMSerializer(); // a DOM will be serialized
   * dser.serialize(inputDoc); // serialize the DOM, sending output to owriter
   * 
   * ser.reset(); // get ready to use the serializer for another document
   *              // of the same output method.
   * </pre>
   * 
   * This interface is a public API.
   * 
   * @see Method
   * @see OutputPropertiesFactory
   * @see SerializerFactory
   * @see DOMSerializer
   * @see ContentHandler
   * 
   * @xsl.usage general
   */
  public interface Serializer {
  
      /**
       * Specifies an output stream to which the document should be
       * serialized. This method should not be called while the
       * serializer is in the process of serializing a document.
       * <p>
       * The encoding specified in the output {@link Properties} is used, or
       * if no encoding was specified, the default for the selected
       * output method.
       * <p>
       * Only one of setWriter() or setOutputStream() should be called.
       *
       * @param output The output stream
       */
      public void setOutputStream(OutputStream output);
  
      /**
       * Get the output stream where the events will be serialized to.
       *
       * @return reference to the result stream, or null if only a writer was
       * set.
       */
      public OutputStream getOutputStream();
  
      /**
       * Specifies a writer to which the document should be serialized.
       * This method should not be called while the serializer is in
       * the process of serializing a document.
       * <p>
       * The encoding specified for the output {@link Properties} must be
       * identical to the output format used with the writer.
       * 
       * <p>
       * Only one of setWriter() or setOutputStream() should be called.
       *
       * @param writer The output writer stream
       */
      public void setWriter(Writer writer);
  
      /**
       * Get the character stream where the events will be serialized to.
       *
       * @return Reference to the result Writer, or null.
       */
      public Writer getWriter();
  
      /**
       * Specifies an output format for this serializer. It the
       * serializer has already been associated with an output format,
       * it will switch to the new format. This method should not be
       * called while the serializer is in the process of serializing
       * a document.
       * <p>
       * The standard property keys supported are: "method", "version", "encoding",
       * "omit-xml-declaration", "standalone", doctype-public",
       * "doctype-system", "cdata-section-elements", "indent", "media-type". 
       * These property keys and their values are described in the XSLT recommendation,
       * see {@link <a href="http://www.w3.org/TR/1999/REC-xslt-19991116"> XSLT 1.0 recommendation</a>}
       * <p>
       * The non-standard property keys supported are defined in {@link OutputPropertiesFactory}.
       *
       * <p>
       * This method can be called multiple times before a document is serialized. Each 
       * time it is called more, or over-riding property values, can be specified. One 
       * property value that can not be changed is that of the "method" property key.
       * <p>
       * The value of the "cdata-section-elements" property key is a whitespace
       * separated list of elements. If the element is in a namespace then 
       * value is passed in this format: {uri}localName 
       * <p>
       * If the "cdata-section-elements" key is specified on multiple calls
       * to this method the set of elements specified in the value
       * is not replaced from one call to the
       * next, but it is cumulative across the calls.
       *
       * @param format The output format to use, as a set of key/value pairs.
       */
      public void setOutputFormat(Properties format);
  
      /**
       * Returns the output format properties for this serializer.
       *
       * @return The output format key/value pairs in use.
       */
      public Properties getOutputFormat();
  
      /**
       * Return a {@link ContentHandler} interface to provide SAX input to.
       * Through the returned object the document to be serailized,
       * as a series of SAX events, can be provided to the serialzier.
       * If the serializer does not support the {@link ContentHandler}
       * interface, it will return null.
       * <p>
       * In principle only one of asDOMSerializer() or asContentHander() 
       * should be called.
       *
       * @return A {@link ContentHandler} interface into this serializer,
       *  or null if the serializer is not SAX 2 capable
       * @throws IOException An I/O exception occured
       */
      public ContentHandler asContentHandler() throws IOException;
  
      /**
       * Return a {@link DOMSerializer} interface into this serializer.
       * Through the returned object the document to be serialized,
       * a DOM, can be provided to the serializer.
       * If the serializer does not support the {@link DOMSerializer}
       * interface, it should return null.
       * <p>
       * In principle only one of asDOMSerializer() or asContentHander() 
       * should be called.
       *
       * @return A {@link DOMSerializer} interface into this serializer,
       *  or null if the serializer is not DOM capable
       * @throws IOException An I/O exception occured
       */
      public DOMSerializer asDOMSerializer() throws IOException;
  
      /**
       * This method resets the serializer. 
       * If this method returns true, the
       * serializer may be used for subsequent serialization of new
       * documents. It is possible to change the output format and
       * output stream prior to serializing, or to reuse the existing
       * output format and output stream or writer.
       *
       * @return True if serializer has been reset and can be reused
       */
      public boolean reset();
  
      /**
       * Return an Object into this serializer to be cast to a DOM3Serializer.
       * Through the returned object the document to be serialized,
       * a DOM (Level 3), can be provided to the serializer.
       * If the serializer does not support casting to a {@link DOM3Serializer}
       * interface, it should return null.
       * <p>
       * In principle only one of asDOM3Serializer() or asContentHander() 
       * should be called.
       *
       * @return An Object to be cast to a DOM3Serializer interface into this serializer,
       *  or null if the serializer is not DOM capable
       * @throws IOException An I/O exception occured
       */
      public Object asDOM3Serializer() throws IOException;
  }
  
  