基于MySQL Connector/C++的数据库连接池
开源中国发表于 2014-08-20 23:02:04
之前发了基于MySQL c语言接口（libmysqlclinet）实现 /*
*File: connection_pool.h
*Author: csc
*/
#ifndef _CONNECTION_POOL_H
#define_CONNECTION_POOL_H
#include <mysql_connection.h>
#include <mysql_driver.h>
#include <cppconn/exception.h>
#include <cppconn/driver.h>
#include <cppconn/connection.h>
#include <cppconn/resultset.h>
#include <cppconn/prepared_statement.h>
#include <cppconn/statement.h>
#include <pthread.h>
#include <list>
using namespace std;
using namespace sql;
class ConnPool {
private:
int curSize; //当前已建立的数据库连接数量
int maxSize; //连接池中定义的最大数据库连接数
string username;
string password;
string url;
list<Connection*> connList; //连接池的容器队列
pthread_mutex_t lock; //线程锁
static ConnPool *connPool;
Driver*driver;
Connection*CreateConnection(); //创建一个连接
void InitConnection(int iInitialSize); //初始化数据库连接池
void DestoryConnection(Connection *conn); //销毁数据库连接对象
void DestoryConnPool(); //销毁数据库连接池
ConnPool(string url, string user, string password, int maxSize); //构造方法
public:
~ConnPool();
Connection*GetConnection(); //获得数据库连接
void ReleaseConnection(Connection *conn); //将数据库连接放回到连接池的容器中
static ConnPool *GetInstance(); //获取数据库连接池对象
};
#endif
/*
* connection_pool.cpp
*
* Created on: 2013-3-29
* Author: csc
*/
#include <stdexcept>
#include <exception>
#include <stdio.h>
#include"connection_pool.h"
using namespace std;
using namespace sql;
ConnPool *ConnPool::connPool = NULL;
//连接池的构造函数
ConnPool::ConnPool(string url, string userName, string password, int maxSize) {
this->maxSize = maxSize;
this->curSize = 0;
this->username = userName;
this->password = password;
this->url = url;
try {
this->driver = sql::mysql::get_driver_instance();
} catch (sql::SQLException&e) {
perror("驱动连接出错;n");
} catch (std::runtime_error&e) {
perror("运行出错了n");
}
this->InitConnection(maxSize / 2);
}
//获取连接池对象，单例模式
ConnPool*ConnPool::GetInstance() {
if (connPool == NULL) {
connPool = new ConnPool("tcp://127.0.0.1:3306","root","123456", 50);
}
return connPool;
}
//初始化连接池，创建最大连接数的一半连接数量
void ConnPool::InitConnection(int iInitialSize) {
Connection*conn;
pthread_mutex_lock(&lock);
for (int i = 0; i < iInitialSize; i++) {
conn = this->CreateConnection();
if (conn) {
connList.push_back(conn);
++(this->curSize);
} else {
perror("创建CONNECTION出错");
}
}
pthread_mutex_unlock(&lock);
}
//创建连接,返回一个Connection
Connection* ConnPool::CreateConnection() {
Connection*conn;
try {
conn = driver->connect(this->url, this->username, this->password); //建立连接
return conn;
} catch (sql::SQLException&e) {
perror("创建连接出错");
return NULL;
} catch (std::runtime_error&e) {
perror("运行时出错");
return NULL;
}
}
//在连接池中获得一个连接
Connection*ConnPool::GetConnection() {
Connection*con;
pthread_mutex_lock(&lock);
if (connList.size() > 0) {//连接池容器中还有连接
con = connList.front(); //得到第一个连接
connList.pop_front(); //移除第一个连接
if (con->isClosed()) {//如果连接已经被关闭，删除后重新建立一个
delete con;
con = this->CreateConnection();
}
//如果连接为空，则创建连接出错
if (con == NULL) {
--curSize;
}
pthread_mutex_unlock(&lock);
return con;
} else {
if (curSize < maxSize) { //还可以创建新的连接
con = this->CreateConnection();
if (con) {
++curSize;
pthread_mutex_unlock(&lock);
return con;
} else {
pthread_mutex_unlock(&lock);
return NULL;
}
} else { //建立的连接数已经达到maxSize
pthread_mutex_unlock(&lock);
return NULL;
}
}
}
//回收数据库连接
void ConnPool::ReleaseConnection(sql::Connection * conn) {
if (conn) {
pthread_mutex_lock(&lock);
connList.push_back(conn);
pthread_mutex_unlock(&lock);
}
}
//连接池的析构函数
ConnPool::~ConnPool() {
this->DestoryConnPool();
}
//销毁连接池,首先要先销毁连接池的中连接
void ConnPool::DestoryConnPool() {
list<Connection*>::iterator icon;
pthread_mutex_lock(&lock);
for (icon = connList.begin(); icon != connList.end(); ++icon) {
this->DestoryConnection(*icon); //销毁连接池中的连接
}
curSize = 0;
connList.clear(); //清空连接池中的连接
pthread_mutex_unlock(&lock);
}
//销毁一个连接
void ConnPool::DestoryConnection(Connection* conn) {
if (conn) {
try {
conn->close();
} catch (sql::SQLException&e) {
perror(e.what());
} catch (std::exception&e) {
perror(e.what());
}
delete conn;
}
}
/*
* main.cpp
*
* Created on: 2013-3-26
* Author: holy
*/
#include"connection_pool.h"
namespace ConnectMySQL {
//初始化连接池
ConnPool *connpool = ConnPool::GetInstance();
void run() {
Connection *con;
Statement *state;
ResultSet *result;
// 从连接池中获取mysql连接
con = connpool->GetConnection();
state = con->createStatement();
state->execute("use holy");
// 查询
result = state->executeQuery("select * from student where id < 1002");
// 输出查询
while (result->next()) {
int id = result->getInt("id");
string name = result->getString("name");
cout << id <<":"<< name << endl;
}
delete state;
connpool->ReleaseConnection(con);
}
}
int main(int argc, char* argv[]) {
ConnectMySQL::run();
return 0;
}
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