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    1   /*
    2    * Copyright 2012 The Netty Project
    3    *
    4    * The Netty Project licenses this file to you under the Apache License,
    5    * version 2.0 (the "License"); you may not use this file except in compliance
    6    * with the 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.ChannelHandler.Sharable;
    25  import org.jboss.netty.channel.ChannelHandlerContext;
    26  import org.jboss.netty.channel.ChannelPipeline;
    27  import org.jboss.netty.channel.MessageEvent;
    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   * @apiviz.landmark
    55   */
    56  @Sharable
    57  public class StringEncoder extends OneToOneEncoder {
    58
    59      // TODO Use CharsetEncoder instead.
    60      private final Charset charset;
    61
    62      /**
    63       * Creates a new instance with the current system character set.
    64       */
    65      public StringEncoder() {
    66          this(Charset.defaultCharset());
    67      }
    68
    69      /**
    70       * Creates a new instance with the specified character set.
    71       */
    72      public StringEncoder(Charset charset) {
    73          if (charset == null) {
    74              throw new NullPointerException("charset");
    75          }
    76          this.charset = charset;
    77      }
    78
    79      /**
    80       * @deprecated Use {@link #StringEncoder(Charset)} instead.
    81       */
    82      @Deprecated
    83      public StringEncoder(String charsetName) {
    84          this(Charset.forName(charsetName));
    85      }
    86
    87      @Override
    88      protected Object encode(
    89              ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
    90          if (!(msg instanceof String)) {
    91              return msg;
    92          }
    93          return copiedBuffer(ctx.getChannel().getConfig().getBufferFactory().getDefaultOrder(), (String) msg, charset);
    94      }
    95  }