vos/metaobjects/property/db_property.cc

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/* $Id: db_property.cc,v 1.7 2002/08/01 07:16:08 tetron Exp $ */

/**
    @file db_property.cc
    
    Implements general interface for property with database backend. This class
    is intended to be subclassed in order to implement MOS-database
    bridges with various SQL-based database systems. Subclasses will
    have to implement the actual updateToDB() and updateFromDB(), and
    methods, and extend the init() method to connect to the database,
    (but call DBProperty::init() to set up query strings)
    as well as any dynamic update when the database changes.

    @author Reed Hedges <reed@zerohour.net>


    This file is part of the Virtual Object System of
    the Interreality project (http://interreality.org).

    Copyright (C) 2001, 2002 Reed Hedges

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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 library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA

*/

#include "db_property.hh"





/* Set up query strings, for getting or changing just data, with constant data type.  */

void DBProperty::init(const string& select_query, const string& update_query, const string& type) {
    select_data_query = select_query;
    update_data_query = update_query;
    force_type = type;
}

/* Set up query strings, for getting or changing both data value and data type.  */
void DBProperty::init(const string& select_all_q, const string& select_data_q, const string& select_type_q, const string& update_all_q, const string& update_data_q, const string& update_type_q) {
    select_all_query = select_all_q;
    select_data_query = select_data_q;
    select_type_query = select_type_q;
    update_all_query = update_all_q;
    update_data_query = update_data_q;
    update_type_query = update_type_q;  // eventually will be removed.
}

/* Use given values to construct standard (I think) SQL query strings. 
*/
void DBProperty::init_components(const string& table, const string& name_col, const string& val_col, const string& type_col, const string& name_val) {
    select_all_query = "SELECT "+val_col+", "+type_col+" FROM "+table+" WHERE "+name_col+" = "+name_val;
    select_data_query = "SELECT "+val_col+" FROM "+table+" WHERE "+name_col+" = "+name_val;
    select_type_query = "SELECT "+type_col+" FROM "+table+" WHERE "+name_col+" = "+name_val;
    update_all_query = "UPDATE "+table+" SET "+val_col+" = \"%d\", "+type_col+" = \"%t\" WHERE "+name_col+" = "+name_val;
    update_data_query = "UPDATE "+table+" SET "+val_col+" = \"%d\" WHERE "+name_col+" = "+name_val;
}

/* fetch stuff from database and change cached variables. */
void DBProperty::updateFromDB() throw(DBAccessError) {
    LOG("DBProperty", 9, "updateFromDB(): querying...");
    string data, type;
    data = queryDB(select_data_query);
    if (force_type == "") {
        // TODO: use select_all_query, then get each part
        type = queryDB(select_type_query);
        if( (data != readRaw()) || (type != getDataType()) ) 
            LocalProperty::replace(queryDB(select_data_query), queryDB(select_type_query));
    } else {
        if(data != readRaw())
            LocalProperty::replace( queryDB(select_data_query), force_type);
    }
}
            
        

/* write data and type to DB. */
void DBProperty::updateToDB() throw(DBAccessError) {

    LOG("DBProperty", 9, "updateToDB(): querying...");
    if(force_type == "") {
        queryDB( sreplace( sreplace(update_all_query, "%d", data), "%t", datatype) );
    } else {
        queryDB( sreplace( update_data_query, "%d", data) );
    }
}



/** replaces substrings. 
    @bug does it replace multiple occurances of key?
*/
string DBProperty::sreplace( const string& s, const string& key, const string& value) throw (range_error) {
    string tmp(s);
    unsigned int k;
    k = s.find(key);
    if(k == s.npos) throw range_error("substring not found.");
    return tmp.replace( k, key.length(), value);
}

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