ReplaceableFilter.java

/*
   Copyright (c) 2012 LinkedIn Corp.

   Licensed 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

       http://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.
 */

/* $Id$ */
package com.linkedin.r2.caprep;

import com.linkedin.r2.filter.NextFilter;
import com.linkedin.r2.filter.message.rest.RestFilter;
import com.linkedin.r2.filter.message.stream.StreamFilter;
import com.linkedin.r2.filter.message.stream.StreamFilterAdapters;
import com.linkedin.r2.message.RequestContext;
import com.linkedin.r2.message.rest.RestRequest;
import com.linkedin.r2.message.rest.RestResponse;
import com.linkedin.r2.message.stream.StreamRequest;
import com.linkedin.r2.message.stream.StreamResponse;
import com.linkedin.util.ArgumentUtil;

import java.util.Map;

/**
 * Filter which delegates all calls to a specified Filter. The delegate can be reset
 * ("replaced") after construction.
 *
 * @author Chris Pettitt
 * @author Zhenkai Zhu
 * @version $Revision$
 */
public class ReplaceableFilter implements RestFilter, StreamFilter
{
  private volatile RestFilter _filter;
  private volatile StreamFilter _adaptedFilter;

  /**
   * Construct a new instance with the specified filter.
   *
   * @param filter Filter to be used as delegate.
   */
  public ReplaceableFilter(RestFilter filter)
  {
    setFilter(filter);
  }

  /**
   * Set the delegate filter.
   *
   * @param filter Filter to be used as delegate.
   */
  public void setFilter(RestFilter filter)
  {
    ArgumentUtil.notNull(filter, "filter");
    _filter = filter;
    if (filter instanceof StreamFilter)
    {
      _adaptedFilter = (StreamFilter) filter;
    }
    else
    {
      _adaptedFilter = StreamFilterAdapters.adaptRestFilter(_filter);
    }
  }

  /**
   * Return the current delegate.
   *
   * @return Filter which is the current delegate.
   */
  public RestFilter getFilter()
  {
    return _filter;
  }

  @Override
  public void onRestRequest(RestRequest req,
                            RequestContext requestContext,
                            Map<String, String> wireAttrs,
                            NextFilter<RestRequest, RestResponse> nextFilter)
  {
    _filter.onRestRequest(req, requestContext, wireAttrs, nextFilter);
  }

  @Override
  public void onRestResponse(RestResponse res,
                             RequestContext requestContext,
                             Map<String, String> wireAttrs,
                             NextFilter<RestRequest, RestResponse> nextFilter)
  {
    _filter.onRestResponse(res, requestContext, wireAttrs, nextFilter);
  }

  @Override
  public void onRestError(Throwable ex,
                          RequestContext requestContext,
                          Map<String, String> wireAttrs,
                          NextFilter<RestRequest, RestResponse> nextFilter)
  {
    _filter.onRestError(ex, requestContext, wireAttrs, nextFilter);
  }

  @Override
  public void onStreamRequest(StreamRequest req, RequestContext requestContext,
                              Map<String, String> wireAttrs,
                              NextFilter<StreamRequest, StreamResponse> nextFilter)
  {
    _adaptedFilter.onStreamRequest(req, requestContext, wireAttrs, nextFilter);
  }

  @Override
  public void onStreamResponse(StreamResponse res, RequestContext requestContext,
                               Map<String, String> wireAttrs,
                               NextFilter<StreamRequest, StreamResponse> nextFilter)
  {
    _adaptedFilter.onStreamResponse(res, requestContext, wireAttrs, nextFilter);
  }

  @Override
  public void onStreamError(Throwable ex, RequestContext requestContext,
                            Map<String, String> wireAttrs,
                            NextFilter<StreamRequest, StreamResponse> nextFilter)
  {
    _adaptedFilter.onStreamError(ex, requestContext, wireAttrs, nextFilter);
  }
}