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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.handler.codec.marshalling;
  
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.util.Attribute;
  import io.netty.util.AttributeKey;
  import org.jboss.marshalling.MarshallerFactory;
  import org.jboss.marshalling.MarshallingConfiguration;
  import org.jboss.marshalling.Unmarshaller;
  
  /**
   * {@link UnmarshallerProvider} which store a reference to the {@link Unmarshaller} in the
   * {@link ChannelHandlerContext} via the {@link ChannelHandlerContext#attr(AttributeKey)}
   * method. So the same {@link Unmarshaller} will be used during the life-time of a {@link Channel}
   * for the {@link ChannelHandler}'s {@link ChannelHandlerContext}.
   *
   *
   */
  public class ContextBoundUnmarshallerProvider extends DefaultUnmarshallerProvider {
  
      private static final AttributeKey<Unmarshaller> UNMARSHALLER = AttributeKey.valueOf(
              ContextBoundUnmarshallerProvider.class, "UNMARSHALLER");
  
      public ContextBoundUnmarshallerProvider(MarshallerFactory factory, MarshallingConfiguration config) {
          super(factory, config);
      }
  
      @Override
      public Unmarshaller getUnmarshaller(ChannelHandlerContext ctx) throws Exception {
          Attribute<Unmarshaller> attr = ctx.channel().attr(UNMARSHALLER);
          Unmarshaller unmarshaller = attr.get();
          if (unmarshaller == null) {
              unmarshaller = super.getUnmarshaller(ctx);
              attr.set(unmarshaller);
          }
          return unmarshaller;
      }
  }