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Basic Connection Example
The following source code is an example of how stale connections are automatically re-connected.
The code demonstrates the the use of the connection ping parameter.
Note that an automatic reconnect will occur once the ping timeout has lapsed if the connection is stale.
/*
* basic_connection application showing the basic generic usage of the dbConnect API
* Copyright (C) 2002 Johnathan Ingram, jingram@rogueware.org
*
* 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 2.1 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 US
*
*/
#include <iostream>
#include <map>
#include <string>
#include <time.h>
#include <stdio.h>
#include "dbconn/dbconnect.h"
#include "dbconn/simpleThreads.h"
using namespace std;
char *tf[] = {"false", "true"};
void
showTableData(
DbQueryVar &conn)
throw(
BaseException)
{
// Execute the same query on both connections
string sqlQuery =
"SELECT "
" id, description "
"FROM "
" TypeTest ";
conn->command(sqlQuery);
conn->execute();
// List the contents of the table
cout << "TypeTest table data: " << endl;
cout << "----------------------------------------- " << endl;
cout << "id\tdescription" << endl;
cout << "--\t-----------" << endl;
if (conn->eof())
cout << "No rows in result set for this query" << endl;
else
{
while (!conn->eof())
{
conn->fetchNext();
cout << conn->getFieldByName("id")->asString() << "\t" << conn->getFieldByName("description")->asString() << endl;
}
}
cout << endl;
}
int
main(
int argc, char** argv)
{
char sql[2048];
map<string, DbConnection::Driver> drivers;
drivers["MYSQL"] = DbConnection::MYSQL;
drivers["MSQL"] = DbConnection::MSQL;
drivers["POSTGRESQL"] = DbConnection::POSTGRESQL;
drivers["DB2"] = DbConnection::DB2;
if (argc == 2)
{
// Use smart pointers. Must be declared outside of the try
// as if an exception is caught it will loose scope and free.
DbConnectionVar driver;
DbQueryVar conn;
try
{
driver = new DbConnection(drivers[argv[1]]);
// Print out the driver information.
DbConnectionDriverInfo* info = driver->getDriverInformation();
cout << "Author : " << info->author << endl;
cout << "Vendor : " << info->vendor << endl;
cout << "Copyright : " << info->copyright << endl;
cout << "Driver Type : " << info->driverType << endl;
cout << "Driver Name : " << info->driverName << endl;
cout << "Description : " << info->driverDescription << endl;
cout << "DbConnect Ver : " << info->dbConnectVersion << endl;
cout << endl;
// Connect to the database. (DB2 takes different conn string)
if (drivers[argv[1]] == DbConnection::DB2)
driver->connect("dbconn", "letmein", "dbConnDB", "", 5, 2);
else
driver->connect("dbconnect", "letmein", "dbConnectDB", "localhost", 5, 2);
// Get a query connection object
conn = driver->requestQueryConnection();
// Set the ping interval on the connection to 1 hour
// Note: This is defaulted to 5 min. So in the event that a connection
// becomes stale, you will receeve errors on the connection for 5 min
// until it is pinged and a new connection to the server established.
// If 5 min is too long, then set it to an acceptable ping interval.
// The more the connection is pinged, the more overhead is introduced.
// The minimum is can be set to is 10 seconds
driver->setPingInterval(1 * 60 * 60);
// Test 1: Connection by doing a query on the TypeTest table
cout << "Test 1: Querying on connection. " << endl;
showTableData(conn);
cout << endl << endl;
// Test 2: Stop the database to make the existing connection stale
cout << "Test 2: Stop and start the database this application is connected to. " << endl;
// Sleep for 10 seconds to make sure the ping interval is exceeded
SimpleThread::sleep(10000);
cout << "Press any key to continue..." << endl;
getchar();
cout << endl << endl;
// Test 3: Do the query again but with the ping interval at one hour forcing an error
cout << "Test 3: Doing query on 'stale' connection. Ping Interval 1 hour" << endl;
cout << " This will generate an error as the ping interval has not been exceeded" << endl;
try
{
showTableData(conn);
cout << "You did not stop / start the database or took more that 1 hour to do so ????" << endl;
exit(1);
}
catch(BaseException &ex)
{
cout << "Expected Error trapped: " << ex.name << " " << ex.code << " : " << ex.description << endl;
}
cout << endl << endl;
// Test 4: Do the query again to make sure the ping establishes a new connection
cout << "Test 4: Doing query on 'stale' connection. Ping interval 10 seconds" << endl;
cout << " This will automatically connect as the ping interval has exceeded..." << endl;
// Set the ping interval on the connection to 10 seconds
driver->setPingInterval(10);
showTableData(conn);
cout << "The reconnection test completed OK" << endl;
cout << endl << endl;
}
catch(BaseException &ex)
{
// Only need to catch a single exception. Can use name etc to determine the actual exception
cout << "DbConnect Exception: " << ex.name << endl
<< " " << ex.code << " : " << ex.description << endl;
}
catch(...)
{
cout << "An Unknown exception has been trapped!\n" << endl;
}
cout << endl;
// The 'conn' and 'driver' objects are smart pointers and will cleanup as soon as they go out of scope
}
else
{
cout << "Syntax: basic_connection DRIVER" << endl;
cout << "Drivers: MYSQL" << endl;
cout << " : MSQL" << endl;
cout << " : POSTGRESQL" << endl;
cout << " : DB2" << endl;
return 1;
}
return 0;
}
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