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    1   /*
    2    * Copyright 2009 Red Hat, Inc.
    3    *
    4    * Red Hat licenses this file to you under the Apache License, version 2.0
    5    * (the "License"); you may not use this file except in compliance with the
    6    * License.  You may obtain a copy of the License at:
    7    *
    8    *    http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
    13   * License for the specific language governing permissions and limitations
    14   * under the License.
    15   */
    16  package org.jboss.netty.handler.codec.string;
    17
    18  import static org.jboss.netty.buffer.ChannelBuffers.*;
    19
    20  import java.nio.charset.Charset;
    21
    22  import org.jboss.netty.buffer.ChannelBuffer;
    23  import org.jboss.netty.channel.Channel;
    24  import org.jboss.netty.channel.ChannelHandlerContext;
    25  import org.jboss.netty.channel.ChannelPipeline;
    26  import org.jboss.netty.channel.MessageEvent;
    27  import org.jboss.netty.channel.ChannelHandler.Sharable;
    28  import org.jboss.netty.handler.codec.frame.DelimiterBasedFrameDecoder;
    29  import org.jboss.netty.handler.codec.frame.Delimiters;
    30  import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
    31
    32  /**
    33   * Encodes the requested {@link String} into a {@link ChannelBuffer}.
    34   * A typical setup for a text-based line protocol in a TCP/IP socket would be:
    35   * <pre>
    36   * {@link ChannelPipeline} pipeline = ...;
    37   *
    38   * // Decoders
    39   * pipeline.addLast("frameDecoder", new {@link DelimiterBasedFrameDecoder}({@link Delimiters#lineDelimiter()}));
    40   * pipeline.addLast("stringDecoder", new {@link StringDecoder}(CharsetUtil.UTF_8));
    41   *
    42   * // Encoder
    43   * pipeline.addLast("stringEncoder", new {@link StringEncoder}(CharsetUtil.UTF_8));
    44   * </pre>
    45   * and then you can use a {@link String} instead of a {@link ChannelBuffer}
    46   * as a message:
    47   * <pre>
    48   * void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
    49   *     String msg = (String) e.getMessage();
    50   *     ch.write("Did you say '" + msg + "'?\n");
    51   * }
    52   * </pre>
    53   *
    54   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    55   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    56   *
    57   * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
    58   *
    59   * @apiviz.landmark
    60   */
    61  @Sharable
    62  public class StringEncoder extends OneToOneEncoder {
    63
    64      // TODO Use CharsetEncoder instead.
    65      private final Charset charset;
    66
    67      /**
    68       * Creates a new instance with the current system character set.
    69       */
    70      public StringEncoder() {
    71          this(Charset.defaultCharset());
    72      }
    73
    74      /**
    75       * Creates a new instance with the specified character set.
    76       */
    77      public StringEncoder(Charset charset) {
    78          if (charset == null) {
    79              throw new NullPointerException("charset");
    80          }
    81          this.charset = charset;
    82      }
    83
    84      /**
    85       * @deprecated Use {@link #StringEncoder(Charset)} instead.
    86       */
    87      @Deprecated
    88      public StringEncoder(String charsetName) {
    89          this(Charset.forName(charsetName));
    90      }
    91
    92      @Override
    93      protected Object encode(
    94              ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
    95          if (!(msg instanceof String)) {
    96              return msg;
    97          }
    98          return copiedBuffer((String) msg, charset);
    99      }
    100 }