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  package org.apache.cayenne;
  
  import org.apache.cayenne.query.Query;
  
  /**
   * An interface of a filter that allows to intercept DataChannel query operations.
   * Query filters allow to implement chains of custom processors around a DataChannel.
   * <p>
   * Example: <pre>{@code
   * public class MyQueryFilter implements DataChannelQueryFilter {
   *     public QueryResponse onQuery(ObjectContext originatingContext, Query query,
   *                                  DataChannelQueryFilterChain filterChain) {
   *         System.out.println("Do something before query");
   *         // process query or return some custom response
   *         QueryResponse response = filterChain.onQuery(originatingContext, query);
   *         System.out.println("Do something after query");
   *         return response;
   *     }
   * }}</pre>
   *
   * @see DataChannelSyncFilter
   * @see org.apache.cayenne.configuration.runtime.CoreModuleExtender#addQueryFilter(DataChannelQueryFilter)
   *
   * @since 4.1
   */
  @FunctionalInterface
  public interface DataChannelQueryFilter {
  
      /**
       * @param originatingContext originating context of query
       * @param query that is processed
       * @param filterChain chain of query filters to invoke after this filter
       * @return query response
       */
      QueryResponse onQuery(ObjectContext originatingContext, Query query, DataChannelQueryFilterChain filterChain);
  
  }
  