content: /*
   * Copyright (c) 2009, 2020, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify it under
   * the terms of the GNU General Public License, version 2.0, as published by the
   * Free Software Foundation.
   *
   * This program is also distributed with certain software (including but not
   * limited to OpenSSL) that is licensed under separate terms, as designated in a
   * particular file or component or in included license documentation. The
   * authors of MySQL hereby grant you an additional permission to link the
   * program and your derivative works with the separately licensed software that
   * they have included with MySQL.
   *
   * Without limiting anything contained in the foregoing, this file, which is
   * part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
   * version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
   * for more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
   */
  
  package com.mysql.cj.interceptors;
  
  import java.util.Properties;
  import java.util.function.Supplier;
  
  import com.mysql.cj.MysqlConnection;
  import com.mysql.cj.Query;
  import com.mysql.cj.log.Log;
  import com.mysql.cj.protocol.Message;
  import com.mysql.cj.protocol.Resultset;
  import com.mysql.cj.protocol.ServerSession;
  
  /**
   * Implement this interface to be placed "in between" query execution, so that you can influence it.
   * 
   * QueryInterceptors are "chainable" when configured by the user, the results returned by the "current" interceptor will be passed on to the next on in the
   * chain, from left-to-right order, as specified by the user in the driver configuration property "queryInterceptors".
   */
  public interface QueryInterceptor {
  
      /**
       * Called once per connection that wants to use the interceptor
       * 
       * The properties are the same ones passed in in the URL or arguments to
       * Driver.connect() or DriverManager.getConnection().
       * 
       * @param conn
       *            the connection for which this interceptor is being created
       * @param props
       *            configuration values as passed to the connection. Note that
       *            in order to support javax.sql.DataSources, configuration properties specific
       *            to an interceptor <strong>must</strong> be passed via setURL() on the
       *            DataSource. QueryInterceptor properties are not exposed via
       *            accessor/mutator methods on DataSources.
       * @param log
       *            logger
       * @return {@link QueryInterceptor}
       */
      QueryInterceptor init(MysqlConnection conn, Properties props, Log log);
  
      /**
       * Called before the given query is going to be sent to the server for processing.
       * 
       * Interceptors are free to return a result set (which must implement the
       * interface {@link Resultset}), and if so,
       * the server will not execute the query, and the given result set will be
       * returned to the application instead.
       * 
       * This method will be called while the connection-level mutex is held, so
       * it will only be called from one thread at a time.
       * 
       * @param sql
       *            the Supplier for SQL representation of the query
       * @param interceptedQuery
       *            the actual {@link Query} instance being intercepted
       * @param <T>
       *            {@link Resultset} object
       * 
       * @return a {@link Resultset} that should be returned to the application instead
       *         of results that are created from actual execution of the intercepted
       *         query.
       */
      <T extends Resultset> T preProcess(Supplier<String> sql, Query interceptedQuery);
  
      /**
       * Called before the given query packet is going to be sent to the server for processing.
       * 
       * Interceptors are free to return a PacketPayload, and if so,
       * the server will not execute the query, and the given PacketPayload will be
       * returned to the application instead.
       * 
       * This method will be called while the connection-level mutex is held, so
       * it will only be called from one thread at a time.
       * 
       * @param queryPacket
       *            original {@link Message}
       * @param <M>
       *            {@link Message} object
       * @return processed {@link Message}
       */
      default <M extends Message> M preProcess(M queryPacket) {
          return null;
      }
  
      /**
       * Should the driver execute this interceptor only for the
       * "original" top-level query, and not put it in the execution
       * path for queries that may be executed from other interceptors?
       * 
       * If an interceptor issues queries using the connection it was created for,
       * and does not return <code>true</code> for this method, it must ensure
       * that it does not cause infinite recursion.
       * 
       * @return true if the driver should ensure that this interceptor is only
       *         executed for the top-level "original" query.
       */
      boolean executeTopLevelOnly();
  
      /**
       * Called by the driver when this extension should release any resources
       * it is holding and cleanup internally before the connection is
       * closed.
       */
      void destroy();
  
      /**
       * Called after the given query has been sent to the server for processing.
       * 
       * Interceptors are free to inspect the "original" result set, and if a
       * different result set is returned by the interceptor, it is used in place
       * of the "original" result set.
       * 
       * This method will be called while the connection-level mutex is held, so
       * it will only be called from one thread at a time.
       * 
       * @param sql
       *            the Supplier for SQL representation of the query
       * @param interceptedQuery
       *            the actual {@link Query} instance being intercepted
       * @param originalResultSet
       *            a {@link Resultset} created from query execution
       * @param serverSession
       *            {@link ServerSession} object after the query execution
       * @param <T>
       *            {@link Resultset} object
       * 
       * @return a {@link Resultset} that should be returned to the application instead
       *         of results that are created from actual execution of the intercepted
       *         query.
       */
      <T extends Resultset> T postProcess(Supplier<String> sql, Query interceptedQuery, T originalResultSet, ServerSession serverSession);
  
      /**
       * Called after the given query packet has been sent to the server for processing.
       * 
       * Interceptors are free to return either a different PacketPayload than the originalResponsePacket or null.
       * 
       * This method will be called while the connection-level mutex is held, so
       * it will only be called from one thread at a time.
       * 
       * @param queryPacket
       *            query {@link Message}
       * @param originalResponsePacket
       *            response {@link Message}
       * @param <M>
       *            {@link Message} object
       * @return {@link Message}
       */
      default <M extends Message> M postProcess(M queryPacket, M originalResponsePacket) {
          return null;
      }
  }
  