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.
   */
  package org.apache.commons.io.output;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.Serializable;
  import java.util.UUID;
  
  import org.apache.commons.io.TaggedIOException;
  
  /**
   * An output stream decorator that tags potential exceptions so that the
   * stream that caused the exception can easily be identified. This is
   * done by using the {@link TaggedIOException} class to wrap all thrown
   * {@link IOException}s. See below for an example of using this class.
   * <pre>
   * TaggedOutputStream stream = new TaggedOutputStream(...);
   * try {
   *     // Processing that may throw an IOException either from this stream
   *     // or from some other IO activity like temporary files, etc.
   *     writeToStream(stream);
   * } catch (IOException e) {
   *     if (stream.isCauseOf(e)) {
   *         // The exception was caused by this stream.
   *         // Use e.getCause() to get the original exception.
   *     } else {
   *         // The exception was caused by something else.
   *     }
   * }
   * </pre>
   * <p>
   * Alternatively, the {@link #throwIfCauseOf(Exception)} method can be
   * used to let higher levels of code handle the exception caused by this
   * stream while other processing errors are being taken care of at this
   * lower level.
   * <pre>
   * TaggedOutputStream stream = new TaggedOutputStream(...);
   * try {
   *     writeToStream(stream);
   * } catch (IOException e) {
   *     stream.throwIfCauseOf(e);
   *     // ... or process the exception that was caused by something else
   * }
   * </pre>
   *
   * @see TaggedIOException
   * @since Commons IO 2.0
   */
  public class TaggedOutputStream extends ProxyOutputStream {
  
      /**
       * The unique tag associated with exceptions from stream.
       */
      private final Serializable tag = UUID.randomUUID();
  
      /**
       * Creates a tagging decorator for the given output stream.
       *
       * @param proxy output stream to be decorated
       */
      public TaggedOutputStream(OutputStream proxy) {
          super(proxy);
      }
  
      /**
       * Tests if the given exception was caused by this stream.
       *
       * @param exception an exception
       * @return <code>true</code> if the exception was thrown by this stream,
       *         <code>false</code> otherwise
       */
      public boolean isCauseOf(Exception exception) {
          return TaggedIOException.isTaggedWith(exception, tag);
      }
  
      /**
       * Re-throws the original exception thrown by this stream. This method
       * first checks whether the given exception is a {@link TaggedIOException}
       * wrapper created by this decorator, and then unwraps and throws the
       * original wrapped exception. Returns normally if the exception was
       * not thrown by this stream.
       *
       * @param exception an exception
       * @throws IOException original exception, if any, thrown by this stream
       */
      public void throwIfCauseOf(Exception exception) throws IOException {
          TaggedIOException.throwCauseIfTaggedWith(exception, tag);
      }
  
      /**
       * Tags any IOExceptions thrown, wrapping and re-throwing.
       *
       * @param e The IOException thrown
       * @throws IOException if an I/O error occurs
       */
      @Override
      protected void handleIOException(IOException e) throws IOException {
          throw new TaggedIOException(e, tag);
      }
  
  }
  