使用連接池管理連接.

在有大量節(jié)點(diǎn)訪問(wèn)的數(shù)據(jù)庫(kù)設(shè)計(jì)中,經(jīng)常要使用到連接池來(lái)管理所有的連接.

一般方法是:建立兩個(gè)連接句柄隊(duì)列,空閑的等待使用的隊(duì)列和正在使用的隊(duì)列.

當(dāng)要查詢時(shí)先從空閑隊(duì)列中獲取一個(gè)句柄,插入到正在使用的隊(duì)列,再用這個(gè)句柄做數(shù)據(jù)庫(kù)操作,完畢后一定要從使用隊(duì)列中刪除,再插入到空閑隊(duì)列.

設(shè)計(jì)代碼如下:

以下為引用的內(nèi)容：

//定義句柄隊(duì)列
typedef std::list<MYSQL *> CONNECTION_HANDLE_LIST;
typedef std::list<MYSQL *>::iterator CONNECTION_HANDLE_LIST_IT;

//連接數(shù)據(jù)庫(kù)的參數(shù)結(jié)構(gòu)
class CDBParameter

{
public:
char *host; ///<主機(jī)名
char *user; ///<用戶名
char *password; ///<密碼
char *database; ///<數(shù)據(jù)庫(kù)名
unsigned int port; ///<端口，一般為0
const char *unix_socket; ///<套接字，一般為NULL
unsigned int client_flag; ///<一般為0
};

//創(chuàng)建兩個(gè)隊(duì)列
CONNECTION_HANDLE_LIST m_lsBusyList; ///<正在使用的連接句柄
CONNECTION_HANDLE_LIST m_lsIdleList; ///<未使用的連接句柄

//所有的連接句柄先連上數(shù)據(jù)庫(kù),加入到空閑隊(duì)列中,等待使用.
bool CDBManager::Connect(char * host /* = "localhost" */, char * user /* = "chenmin" */, \
char * password /* = "chenmin" */, char * database /* = "HostCache" */)
{
CDBParameter * lpDBParam = new CDBParameter();
lpDBParam->host = host;
lpDBParam->user = user;
lpDBParam->password = password;
lpDBParam->database = database;
lpDBParam->port = 0;
lpDBParam->unix_socket = NULL;
lpDBParam->client_flag = 0;
try
{
//連接
for(int index = 0; index < CONNECTION_NUM; index++)
{
MYSQL * pConnectHandle = mysql_init((MYSQL*) 0); //初始化連接句柄
if(!mysql_real_connect(pConnectHandle, lpDBParam->host, lpDBParam->user, lpDBParam->password,\
lpDBParam->database,lpDBParam->port,lpDBParam->unix_socket,lpDBParam->client_fla))
return false;
//加入到空閑隊(duì)列中
m_lsIdleList.push_back(pConnectHandle);
}
}
catch(...)
{
return false;
}
return true;
}

//提取一個(gè)空閑句柄供使用
MYSQL * CDBManager::GetIdleConnectHandle()
{
MYSQL * pConnectHandle = NULL;
m_ListMutex.acquire();
if(m_lsIdleList.size())
{
pConnectHandle = m_lsIdleList.front();
m_lsIdleList.pop_front();
m_lsBusyList.push_back(pConnectHandle);
}
else //特殊情況,閑隊(duì)列中為空,返回為空
{
pConnectHandle = 0;
}
m_ListMutex.release();

return pConnectHandle;
}

//從使用隊(duì)列中釋放一個(gè)使用完畢的句柄,插入到空閑隊(duì)列
void CDBManager::SetIdleConnectHandle(MYSQL * connecthandle)
{
m_ListMutex.acquire();
m_lsBusyList.remove(connecthandle);
m_lsIdleList.push_back(connecthandle);
m_ListMutex.release();
}
//使用示例,首先獲取空閑句柄,利用這個(gè)句柄做真正的操作,然后再插回到空閑隊(duì)列
bool CDBManager::DeleteHostCacheBySessionID(char * sessionid)
{
MYSQL * pConnectHandle = GetIdleConnectHandle();
if(!pConnectHandle)
return 0;
bool bRet = DeleteHostCacheBySessionID(pConnectHandle, sessionid);
SetIdleConnectHandle(pConnectHandle);
return bRet;
}
//傳入空閑的句柄,做真正的刪除操作
bool CDBManager::DeleteHostCacheBySessionID(MYSQL * connecthandle, char * sessionid)
{
char deleteSQL[SQL_LENGTH];
memset(deleteSQL, 0, sizeof(deleteSQL));
sprintf(deleteSQL,"delete from HostCache where SessionID = '%s'", sessionid);
if(mysql_query(connecthandle,deleteSQL) != 0) //刪除
return false;
return true;
}

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