Examples of org.apache.nutch.io.Writable

org.apache.nutch.io.Writable
A simple, efficient, serialization protocol, based on {@link DataInput} and{@link DataOutput}.
Implementations typically implement a static read(DataInput) method which constructs a new instance, calls {@link #readFields(DataInput)}, and returns the instance. @author Doug Cutting

  /** Called for each call. */
  public abstract Writable call(Writable param) throws IOException;


  
  private Writable makeParam() {
    Writable param;                               // construct param
    try {
      param = (Writable)paramClass.newInstance();
    } catch (InstantiationException e) {
      throw new RuntimeException(e.toString());
    } catch (IllegalAccessException e) {

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          }
        
          if (LOG.isLoggable(Level.FINE))
            LOG.fine(getName() + " got #" + id);
        
          Writable param = makeParam();           // read param
          param.readFields(in);        
        
          Call call = new Call(id, param, this);
        
          synchronized (callQueue) {
            callQueue.addLast(call);              // queue the call

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          if (LOG.isLoggable(Level.FINE))
            LOG.fine(getName() + ": has #" + call.id + " from " +
                     call.connection.socket.getInetAddress().getHostAddress());
          
          String error = null;
          Writable value = null;
          try {
            value = call(call.param);             // make the call
          } catch (IOException e) {
            LOG.log(Level.INFO, getName() + " call error: " + e, e);
            error = e.getMessage();
          } catch (Exception e) {
            LOG.log(Level.INFO, getName() + " call error: " + e, e);
            error = e.toString();
          }
            
          DataOutputStream out = call.connection.out;
          synchronized (out) {
            out.writeInt(call.id);                // write call id
            out.writeBoolean(error!=null);        // write error flag
            if (error != null)
              value = new UTF8(error);
            value.write(out);                     // write value
            out.flush();
          }


        } catch (Exception e) {
          LOG.log(Level.INFO, getName() + " caught: " + e, e);

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    }
    return connection;
  }


  private Writable makeValue() {
    Writable value;                             // construct value
    try {
      value = (Writable)valueClass.newInstance();
    } catch (InstantiationException e) {
      throw new RuntimeException(e.toString());
    } catch (IllegalAccessException e) {

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            UTF8 utf8 = new UTF8();
            utf8.readFields(in);                  // read error string
            call.error = utf8.toString();
            call.value = null;
          } else {
            Writable value = makeValue();
            value.readFields(in);                 // read value
            call.value = value;
            call.error = null;
          }
          call.callComplete();                   // deliver result to caller
        }

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Related Classes of org.apache.nutch.io.Writable

org.apache.nutch.ipc.Client

org.apache.nutch.ipc.Client$Connection

org.apache.nutch.ipc.Server

org.apache.nutch.ipc.Server$Connection

org.apache.nutch.ipc.Server$Handler

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