valueidentitystatementcachekey.java

c3p0数据库连接池实现源码

/*
 * Distributed as part of c3p0 v.0.9.1-pre6
 *
 * Copyright (C) 2005 Machinery For Change, Inc.
 *
 * Author: Steve Waldman <[e-mail]>
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2.1, as 
 * published by the Free Software Foundation.
 *
 * This software 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this software; see the file LICENSE.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */


package com.mchange.v2.c3p0.stmt;

import java.sql.Connection;
import java.sql.ResultSet;
import java.lang.reflect.Method;
import com.mchange.v2.coalesce.*;

import java.sql.Connection;
import java.sql.ResultSet;
import java.lang.reflect.Method;
import com.mchange.v2.coalesce.*;

final class ValueIdentityStatementCacheKey extends StatementCacheKey
{
    //MT: not thread-safe, but protected within the find() method
    //    by StatementCacheKey.class lock
    final static Coalescer keyCoalescer;

    //MT: modified only within StatementCacheKey.class-locked find() method
    static ValueIdentityStatementCacheKey spare = new ValueIdentityStatementCacheKey();

    static 
    {
	CoalesceChecker cc = new CoalesceChecker()
	    {
		public boolean checkCoalesce( Object a, Object b )
		{ return StatementCacheKey.equals( (StatementCacheKey) a, b ); }

		public int coalesceHash( Object a )
		{ return ((ValueIdentityStatementCacheKey) a).cached_hash; }
	    }; 
	
	//make weak, unsync'ed coalescer
	keyCoalescer = CoalescerFactory.createCoalescer( cc, true, false );
    }

    static StatementCacheKey _find( Connection pcon, Method stmtProducingMethod, Object[] args )
    {
	///BEGIN FIND LOGIC///
	String stmtText = (String) args[0];
	boolean is_callable = stmtProducingMethod.getName().equals("prepareCall");
	int result_set_type;
	int result_set_concurrency;

	int[] columnIndexes;
	String[] columnNames;
	Integer autogeneratedKeys;
	Integer resultSetHoldability;

	if (args.length == 1)
	    {
		result_set_type        = ResultSet.TYPE_FORWARD_ONLY;
		result_set_concurrency = ResultSet.CONCUR_READ_ONLY;
		columnIndexes          = null;
		columnNames            = null;
		autogeneratedKeys      = null;
		resultSetHoldability   = null;
	    }
	else if (args.length == 2)
	    {
		Class[] argTypes = stmtProducingMethod.getParameterTypes();
		if (argTypes[1].isArray())
		    {
			Class baseType = argTypes[1].getComponentType();
			if (baseType == int.class) //second arg is columnIndexes
			    {
				result_set_type        = ResultSet.TYPE_FORWARD_ONLY;
				result_set_concurrency = ResultSet.CONCUR_READ_ONLY;
				columnIndexes          = (int[]) args[1];
				columnNames            = null;
				autogeneratedKeys      = null;
				resultSetHoldability   = null;
			    }
			else if (baseType == String.class)
			    {
				result_set_type        = ResultSet.TYPE_FORWARD_ONLY;
				result_set_concurrency = ResultSet.CONCUR_READ_ONLY;
				columnIndexes          = null;
				columnNames            = (String[]) args[1];
				autogeneratedKeys      = null;
				resultSetHoldability   = null;
			    }
			else
			    throw new IllegalArgumentException("c3p0 probably needs to be updated for some new " +
							       "JDBC spec! As of JDBC3, we expect two arg statement " +
							       "producing methods where the second arg is either " +
							       "an int, int array, or String array.");
		    }
		else //it should be a boxed int, autogeneratedKeys
		    {
			result_set_type        = ResultSet.TYPE_FORWARD_ONLY;
			result_set_concurrency = ResultSet.CONCUR_READ_ONLY;
			columnIndexes          = null;
			columnNames            = null;
			autogeneratedKeys      = (Integer) args[1];
			resultSetHoldability   = null;
		    }
	    }
	else if (args.length == 3)
	    {
		result_set_type        = ((Integer) args[1]).intValue();
		result_set_concurrency = ((Integer) args[2]).intValue();
		columnIndexes          = null;
		columnNames            = null;
		autogeneratedKeys      = null;
		resultSetHoldability   = null;
	    }
	else if (args.length == 4)
	    {
		result_set_type        = ((Integer) args[1]).intValue();
		result_set_concurrency = ((Integer) args[2]).intValue();
		columnIndexes          = null;
		columnNames            = null;
		autogeneratedKeys      = null;
		resultSetHoldability   = (Integer) args[3];
	    }
	else
	    throw new IllegalArgumentException("Unexpected number of args to " + 
					       stmtProducingMethod.getName() );
	///END FIND LOGIC///


	// we keep around a "spare" and initialize it over and over again
	// rather than allocating, because usually we'll find the statement we're
	// looking for is already in the coalescer, and we can avoid the
	// allocation altogether.
  	spare.init( pcon, 
		    stmtText, 
		    is_callable, 
		    result_set_type, 
		    result_set_concurrency,
		    columnIndexes,
		    columnNames,
		    autogeneratedKeys,
		    resultSetHoldability );

  	StatementCacheKey out = (StatementCacheKey) keyCoalescer.coalesce( spare );

//   	System.err.println( "StatementCacheKey -> " + out );
//   	System.err.println( "Key is coalesced already? " + (out != spare) );
//   	System.err.println( "Keys in coalescer: " + keyCoalescer.countCoalesced() );

	if (out == spare)
	    spare = new ValueIdentityStatementCacheKey();
	return out;
    }

    void init( Connection physicalConnection,
	       String stmtText,
	       boolean is_callable,
	       int result_set_type,
	       int result_set_concurrency,
	       int[] columnIndexes,
	       String[] columnNames,
	       Integer autogeneratedKeys,
	       Integer resultSetHoldability )
    {
	super.init( physicalConnection,
		    stmtText,
		    is_callable,
		    result_set_type,
		    result_set_concurrency,
		    columnIndexes,
		    columnNames,
		    autogeneratedKeys,
		    resultSetHoldability );
	this.cached_hash = StatementCacheKey.hashCode( this );
    }

    // extra instance varieable
    int cached_hash;

    // Note that we DON'T override equals() or hashCode() here -- each instance let the coalescer guarantee a
    // single instance exists that would equals() it (that is, itself), and we rely on Object's default equals() and
    // hashCode methods do their thangs.
}