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;
  
  /**
   * It is unfortunate that java.io.Writer is a class rather than an interface.
   * The serializer has a number of classes that extend java.io.Writer
   * and which send their ouput to a yet another wrapped Writer or OutputStream.
   * 
   * The purpose of this interface is to force such classes to over-ride all of
   * the important methods defined on the java.io.Writer class, namely these:
   * <code>
   * write(int val)
   * write(char[] chars)
   * write(char[] chars, int start, int count)
   * write(String chars)
   * write(String chars, int start, int count)
   * flush()
   * close()
   * </code>
   * In this manner nothing will accidentally go directly to 
   * the base class rather than to the wrapped Writer or OutputStream. 
   * 
   * The purpose of this class is to have a uniform way of chaining the output of one writer to
   * the next writer in the chain. In addition there are methods to obtain the Writer or 
   * OutputStream that this object sends its output to.
   * 
   * This interface is only for internal use withing the serializer. 
   * @xsl.usage internal
   */
  interface WriterChain
  {
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void write(int val) throws IOException;
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void write(char[] chars) throws IOException;
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void write(char[] chars, int start, int count) throws IOException;
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void write(String chars) throws IOException;
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void write(String chars, int start, int count) throws IOException;
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void flush() throws IOException;
      /** This method forces us to over-ride the method defined in java.io.Writer */
      public void close() throws IOException;
  
      /**
       * If this method returns null, getOutputStream() must return non-null.
       * Get the writer that this writer sends its output to.
       * 
       * It is possible that the Writer returned by this method does not
       * implement the WriterChain interface.
       */
      public java.io.Writer getWriter();
      
      /**
       * If this method returns null, getWriter() must return non-null.
       * Get the OutputStream that this writer sends its output to.
       */
      public java.io.OutputStream getOutputStream();
  }
  