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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.example.factorial;
    17
    18  import java.math.BigInteger;
    19  import java.util.Formatter;
    20  import java.util.logging.Level;
    21  import java.util.logging.Logger;
    22
    23  import org.jboss.netty.channel.ChannelEvent;
    24  import org.jboss.netty.channel.ChannelHandlerContext;
    25  import org.jboss.netty.channel.ChannelStateEvent;
    26  import org.jboss.netty.channel.ExceptionEvent;
    27  import org.jboss.netty.channel.MessageEvent;
    28  import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
    29
    30  /**
    31   * Handler for a server-side channel.  This handler maintains stateful
    32   * information which is specific to a certain channel using member variables.
    33   * Therefore, an instance of this handler can cover only one channel.  You have
    34   * to create a new handler instance whenever you create a new channel and insert
    35   * this handler  to avoid a race condition.
    36   */
    37  public class FactorialServerHandler extends SimpleChannelUpstreamHandler {
    38
    39      private static final Logger logger = Logger.getLogger(
    40              FactorialServerHandler.class.getName());
    41
    42      // Stateful properties.
    43      private int lastMultiplier = 1;
    44      private BigInteger factorial = new BigInteger(new byte[] { 1 });
    45
    46      @Override
    47      public void handleUpstream(
    48              ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
    49          if (e instanceof ChannelStateEvent) {
    50              logger.info(e.toString());
    51          }
    52          super.handleUpstream(ctx, e);
    53      }
    54
    55      @Override
    56      public void messageReceived(
    57              ChannelHandlerContext ctx, MessageEvent e) {
    58
    59          // Calculate the cumulative factorial and send it to the client.
    60          BigInteger number;
    61          if (e.getMessage() instanceof BigInteger) {
    62              number = (BigInteger) e.getMessage();
    63          } else {
    64              number = new BigInteger(e.getMessage().toString());
    65          }
    66          lastMultiplier = number.intValue();
    67          factorial = factorial.multiply(number);
    68          e.getChannel().write(factorial);
    69      }
    70
    71      @Override
    72      public void channelDisconnected(ChannelHandlerContext ctx,
    73              ChannelStateEvent e) throws Exception {
    74          logger.info(new Formatter().format(
    75                  "Factorial of %,d is: %,d", lastMultiplier, factorial).toString());
    76      }
    77
    78      @Override
    79      public void exceptionCaught(
    80              ChannelHandlerContext ctx, ExceptionEvent e) {
    81          logger.log(
    82                  Level.WARNING,
    83                  "Unexpected exception from downstream.",
    84                  e.getCause());
    85          e.getChannel().close();
    86      }
    87  }