大家好，我是考100分的小小码 ，祝大家学习进步，加薪顺利呀。今天说一说MySQL预处理「建议收藏」,希望您对编程的造诣更进一步.
C++预处理接口:
preparable_stmt 语句中的? 是个占位符，字符串类型需要加上单引号。
创建预处理对象sql::PreparedStatement* tPreStmt = db_conn->prepareStatement(“update user_table set user_level=? where user_id=?”);
参数设置接口：setBigInt，setBlob，setBoolean，setDateTime，setDouble，setInt，setUInt，setInt64，setUInt64，setNull，setString。
每次调用结束之后需要调用clearParameters接口清空参数，方便下次调用。
实例代码：
#pragma once
#include <iostream>
#include <string>
#include <map>
#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>
int main()
{
std::string url = "127.0.0.1:3306";
std::string user = "test";
std::string passwd = "123";
sql::Driver* driver = sql::mysql::get_driver_instance();
if (driver)
{
sql::Connection* conn = driver->connect(url, user, passwd);
if (conn == nullptr)
{
return -1;
}
std::string stmt_str = "update user_table set user_level=? where user_id=?";
sql::PreparedStatement* preStmt = m_conn->prepareStatement(stmt_str);
preStmt->setUInt(0,1);
preStmt->setUInt64(1,132129938);
preStmt->executeUpdate();
}
else
{
return -1;
}
return 0;
}代码100分
项目实践中不会有这么简单的逻辑，通常需要在每个连接中初始化好预处理语句，甚至还需要建立MySql连接池，下面给出一个示例代码：
代码100分#pragma once
#include <iostream>
#include <string>
#include <map>
#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>
class MysqlConn
{
public:
MysqlConn();
~MysqlConn();
bool ConnectDb(const std::string& url, const std::string& user, const std::string& passwd);
bool AddPreStatement(int id, const std::string& stmts);
sql::Connection* GetConn() { return m_conn; }
sql::PreparedStatement* GetPreStatement(int id);
private:
std::string m_url;
std::string m_user;
std::string m_passwd;
sql::Driver* m_driver = nullptr;
sql::Connection* m_conn = nullptr;
std::map<int, sql::PreparedStatement*> m_stmts;
};
MysqlConn::MysqlConn()
{
}
MysqlConn::~MysqlConn()
{
std::map<int, sql::PreparedStatement*>::iterator it = m_stmts.begin();
while (it != m_stmts.end())
{
delete it->second;
it->second = nullptr;
it++;
}
m_stmts.clear();
if (m_conn)
{
m_conn->close();
delete m_conn;
m_conn = nullptr;
}
}
bool MysqlConn::ConnectDb(const std::string& url, const std::string& user, const std::string& passwd)
{
m_url = url;
m_user = user;
m_passwd = passwd;
m_driver = sql::mysql::get_driver_instance();
if (m_driver)
{
m_conn = m_driver->connect(m_url, m_user, m_passwd);
if (m_conn == nullptr)
{
return false;
}
}
else
{
return false;
}
return true;
}
bool MysqlConn::AddPreStatement(int id, const std::string& stmts)
{
sql::PreparedStatement* tVal = m_conn->prepareStatement(stmts);
if (!tVal)
{
return false;
}
std::map<int, sql::PreparedStatement*>::iterator it = m_stmts.find(id);
if (it != m_stmts.end())
{
delete it->second;
it->second = tVal;
}
else
{
m_stmts[id] = tVal;
}
return true;
}
sql::PreparedStatement* MysqlConn::GetPreStatement(int id)
{
std::map<int, sql::PreparedStatement*>::iterator it = m_stmts.find(id);
if (it != m_stmts.end())
{
it->second->clearParameters();
return it->second;
}
return nullptr;
}
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