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StatementInterceptor.java

/*
 Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 

  The MySQL Connector/J is licensed under the terms of the GPLv2
  <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most MySQL Connectors.
  There are special exceptions to the terms and conditions of the GPLv2 as it is applied to
  this software, see the FLOSS License Exception
  <http://www.mysql.com/about/legal/licensing/foss-exception.html>.

  This program is free software; you can redistribute it and/or modify it under the terms
  of the GNU General Public License as published by the Free Software Foundation; version 2
  of the License.

  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 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.jdbc;

import java.sql.SQLException;
import java.util.Properties;

/**
 * Implement this interface to be placed "in between" query execution, so that
 * you can influence it. (currently experimental).
 * 
 * StatementInterceptors 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 
 * JDBC configuration property "statementInterceptors".
 * 
 * @version $Id: $
 */

00042 public interface StatementInterceptor extends Extension {

      /**
       * 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. StatementInterceptor properties are not exposed via 
       * accessor/mutator methods on DataSources.
       * 
       * @throws SQLException should be thrown if the the StatementInterceptor
       * can not initialize itself.
       */
      
      public abstract void init(Connection conn, Properties props) throws SQLException;

      /**
       * Called before the given statement is going to be sent to the
       * server for processing.
       * 
       * Interceptors are free to return a result set (which must implement the
       * interface com.mysql.jdbc.ResultSetInternalMethods), 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 SQL representation of the statement
       * @param interceptedStatement the actual statement instance being intercepted
       * @param connection the connection the statement is using (passed in to make
       * thread-safe implementations straightforward)
       * 
       * @return a result set that should be returned to the application instead
       * of results that are created from actual execution of the intercepted 
       * statement.
       * 
       * @throws SQLException if an error occurs during execution
       * 
       * @see com.mysql.jdbc.ResultSetInternalMethods
       */

      public abstract ResultSetInternalMethods preProcess(String sql,
                  Statement interceptedStatement, Connection connection)
                  throws SQLException;

      /**
       * Called after the given statement 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. (the result set returned by the interceptor
       * must implement the interface
       * com.mysql.jdbc.ResultSetInternalMethods).
       * 
       * 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 SQL representation of the statement
       * @param interceptedStatement the actual statement instance being intercepted
       * @param connection the connection the statement is using (passed in to make
       * thread-safe implementations straightforward)
       * 
       * @return a result set that should be returned to the application instead
       * of results that are created from actual execution of the intercepted 
       * statement.
       * 
       * @throws SQLException if an error occurs during execution
       * 
       * @see com.mysql.jdbc.ResultSetInternalMethods
       */
      public abstract ResultSetInternalMethods postProcess(String sql,
                  Statement interceptedStatement,
                  ResultSetInternalMethods originalResultSet,
                  Connection connection) throws SQLException;
      
      /**
       * 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.
       */
      public abstract boolean executeTopLevelOnly();

      /**
       * Called by the driver when this extension should release any resources
       * it is holding and cleanup internally before the connection is
       * closed.
       */
      public abstract void destroy();
}

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