Linux MySQL Connector/C++ 编程实例

本篇文章介绍如何在Linux平台使用Connector/C++ 连接数据库，假定MySQL已经安装完成。如果还没有安装MySQL，请先安装。MySQL版本：8.0.19

1. 安装Connector/C++

2. 编写代码

3. 创建数据库

4. 可能遇到的编译问题解决方案

参考文档：

示例是一个图书馆管理系统，拥有添加、删除、修改、查询功能。先看下实现效果图：

在看具体代码之前，先看下示例的设计文档：

下面进入正式教程：

1. 安装Connector/C++

下载地址（https://dev.mysql.com/downloads/connector/cpp/）。

下载解压完成后，如下图：

lib64存放库文件，include存放头文件。

2. 编写代码

新建library目录。然后在该目录下新建三个文件。library_main.cpp, library_sql.h， library_book.h Makefile 。代码如下：

library_main.cpp

/**  Desc: Linux c++ MySQL 示例，图书馆管理系统，主程序*  Author: mason*  Date: 20200203*/#include "library_book.h"
#include "library_sql.h"#define LIBRARY_ADD_BOOK    1   // 添加
#define LIBRARY_DELETE_BOOK 2   // 删除
#define LIBRARY_UPDATE_BOOK 3   // 修改
#define LIBRARY_QUERY_BOOK  4   // 查询
#define LIBRARY_QUIT        5   // 退出// MySQL单例类静态变量初始化
sql::Driver* sql_loader::driver = nullptr;
sql::Connection* sql_loader::con = nullptr;
sql::Statement* sql_loader::stmt = nullptr;
sql::ResultSet* sql_loader::res = nullptr;
bool sql_loader::init = false;// 系统使用说明
void Usage()
{cout<<"\n欢迎使用图书管理系统\n""1:添加图书\n""2:删除图书\n""3:修改图书\n""4:查询图书\n""5:退出系统\n"<<endl;return ;
}// 读取图书信息
void ReadBook(Book &new_book)
{cout<<"请输入添加的书名：";cin>>new_book.book_name;cout<<"请输入作者：";cin>>new_book.author;//cout<<"[DEBUG]"<<author<<endl;cout<<"请输入价格：";cin>>new_book.price;cout<<"请输入数量：";cin>>new_book.quantity;return ;
}int main()
{bool is_quit = false;int op_code = -1, book_id;string book_name, author;unsigned int price, quantity;Book new_book;vector<Book> book_list;// 主循环while (!is_quit){Usage();cout<<"请输入你的选择:";cin>>op_code;switch (op_code){// 添加操作case LIBRARY_ADD_BOOK:// 读取图书信息ReadBook(new_book);sql_loader::add(new_book);break;// 删除操作case LIBRARY_DELETE_BOOK:    sql_loader::delete_book();break;// 修改操作case LIBRARY_UPDATE_BOOK:    cout<<"请输入待修改的编号：";cin>>new_book.id;ReadBook(new_book);sql_loader::update(new_book);break;        // 查询操作case LIBRARY_QUERY_BOOK:            sql_loader::query(book_list);// 打印查询结果cout << "------------- 查询开始 ----------------" <<endl;for (auto &iter : book_list){   cout <<"编号： "<< iter.id << endl;cout <<"书名： "<< iter.book_name << endl;cout <<"作者： "<< iter.author << endl;cout <<"数量： "<< iter.quantity << endl;cout <<"价格： "<< iter.price << endl;cout << "-----------------------------" <<endl;}            cout << "------------- 查询结束 ----------------" <<endl;// 清空上次查询结果book_list.erase(book_list.begin(), book_list.end());break;// 退出系统        case LIBRARY_QUIT:is_quit = true;break;      default:cout<<"未识别的操作："<<op_code<<endl;break;}}cout<<"感谢使用"<<endl;return 0;
}

library_book.h

 /**  Desc: Linux c++ MySQL 示例，图书馆管理系统，图书类*  Author: mason*  Date: 20200203*/#pragma once
#include <string>
#include <iostream>using namespace std;class Book
{public:int id;                      // 图书编号string book_name;            // 书名string author;               // 作者unsigned int price;          // 价格unsigned int quantity;       // 数量public:// 默认构造函数Book(){}// 含参构造函数Book(string book_name, string author, int price, int quantity, int book_id = 0):book_name(book_name),author(author),price(price),quantity(quantity), id(book_id){}// 析构函数    ~Book(){}
};

library_sql.h

/**  Desc: Linux c++ MySQL 示例，图书馆管理系统，MySQL单例*  Author: mason*  Date: 20200203*/#pragma once#include <vector>
#include "library_book.h"
#include <mysql_connection.h>#include <cppconn/driver.h>
#include <cppconn/exception.h>
#include <cppconn/resultset.h>
#include <cppconn/statement.h>#define SQL_QUERY_ALL           0   // 查询所有
#define SQL_QUERY_BY_AUTHOR     1   // 查询作者
#define SQL_QUERY_BY_ID         2   // 查询编号
#define SQL_QUERY_BY_BOOK_NAME  3   // 查询书名#define SQL_DELETE_ALL           0   // 删除所有
#define SQL_DELETE_BY_AUTHOR     1   // 删除作者
#define SQL_DELETE_BY_ID         2   // 删除编号
#define SQL_DELETE_BY_BOOK_NAME  3   // 删除书名using namespace std;class sql_loader
{public:static sql::Driver *driver;static sql::Connection *con;static sql::Statement *stmt;static sql::ResultSet *res;static bool init;// sql 初始化static void sql_loader_init(){if (sql_loader::init){cout<<"sql 已经完成初始化"<<endl;return ;}/* Create a connection */driver = get_driver_instance();// 密码和用户名con = driver->connect("tcp://127.0.0.1:3306", "root", "123456");/* Connect to the MySQL test database ，数据库名*/con->setSchema("library");init = true;cout<<"sql 初始化成功"<<endl;return ;}// 添加图书static void add(Book &new_book){// SQL初始化sql_loader_init();// 创建并构造sql语句，用完后手动删除stmt = con->createStatement();string sql_cmd = "INSERT INTO books(name, author, price, quantity) VALUES ('";sql_cmd.append(new_book.book_name);sql_cmd.append("','");sql_cmd.append(new_book.author);sql_cmd.append("', ");sql_cmd.append(to_string(new_book.price));sql_cmd.append(", ");sql_cmd.append(to_string(new_book.quantity));sql_cmd.append(")");cout<<"insert cmd : "<<sql_cmd<<endl;try{stmt->execute(sql_cmd);} catch (sql::SQLException &e) {cout << "# ERR: SQLException in " << __FILE__;cout << "(" << __FUNCTION__ << ") on line "<< __LINE__ << endl;cout << "# ERR: " << e.what();cout << " (MySQL error code: " << e.getErrorCode();cout << ", SQLState: " << e.getSQLState() << " )" << endl;}// 删除资源delete stmt;return ;}// 修改图书static void update(Book& new_book){// SQL初始化sql_loader_init();// 创建并构造sql语句，用完后手动删除            stmt = con->createStatement();string sql_cmd = "update books set name='";sql_cmd.append(new_book.book_name);sql_cmd.append("', author='");sql_cmd.append(new_book.author);sql_cmd.append("', price=");sql_cmd.append(to_string(new_book.price));sql_cmd.append(", quantity=");sql_cmd.append(to_string(new_book.quantity));sql_cmd.append(" where id=");sql_cmd.append(to_string(new_book.id));cout<<"update cmd : "<<sql_cmd<<endl;try{stmt->execute(sql_cmd);} catch (sql::SQLException &e) {cout << "# ERR: SQLException in " << __FILE__;cout << "(" << __FUNCTION__ << ") on line "<< __LINE__ << endl;cout << "# ERR: " << e.what();cout << " (MySQL error code: " << e.getErrorCode();cout << ", SQLState: " << e.getSQLState() << " )" << endl;}// 释放资源delete stmt;return ;            }// 删除图书static void delete_book(){int op_code = -1, book_id;string author, book_name;string sql_cmd = "delete from books";cout<<"请输入删除方式：\n""0: 删除所有图书\n""1: 删除指定作者\n""2: 删除指定编号\n""3: 删除指定图书"<<endl;cin>>op_code;switch (op_code){case SQL_DELETE_ALL:break;case SQL_DELETE_BY_AUTHOR:cout<<"请输入要删除的作者：";cin>>author;sql_cmd.append(" where author='");sql_cmd.append(author);sql_cmd.append("'");break;case SQL_DELETE_BY_ID:cout<<"请输入要删除的编号：";cin>>book_id;sql_cmd.append(" where id=");sql_cmd.append(to_string(book_id));             break;case SQL_DELETE_BY_BOOK_NAME:cout<<"请输入要删除的书名：";cin>>book_name;sql_cmd.append(" where name='");sql_cmd.append(book_name);sql_cmd.append("'");                break;default:cout<<"不存在 "<<op_code<<" 对应的删除方式，删除失败"<<endl;return ;}cout<<"delete cmd : "<<sql_cmd<<endl;// 初始化SQLsql_loader_init();// 创建并构造sql语句，用完后手动删除            stmt = con->createStatement();try{// 执行SQL语句stmt->execute(sql_cmd);// 释放资源delete stmt;} catch (sql::SQLException &e) {cout << "# ERR: SQLException in " << __FILE__;cout << "(" << __FUNCTION__ << ") on line "<< __LINE__ << endl;cout << "# ERR: " << e.what();cout << " (MySQL error code: " << e.getErrorCode();cout << ", SQLState: " << e.getSQLState() << " )" << endl;}return ;            }// 查询图书static void query(vector<Book>& book_list){int op_code = -1, book_id;string author, book_name;string sql_cmd = "select id, name, author, quantity, price from books";cout<<"请输入查询方式：\n""0: 查询所有\n""1: 查询作者\n""2: 查询编号\n""3: 查询书名"<<endl;cin>>op_code;switch (op_code){case SQL_QUERY_ALL:break;case SQL_QUERY_BY_AUTHOR:cout<<"请输入要查询的作者：";cin>>author;sql_cmd.append(" where author='");sql_cmd.append(author);sql_cmd.append("'");break;case SQL_QUERY_BY_ID:cout<<"请输入要查询的编号：";cin>>book_id;sql_cmd.append(" where id=");sql_cmd.append(to_string(book_id));             break;case SQL_QUERY_BY_BOOK_NAME:cout<<"请输入要查询的书名：";cin>>book_name;sql_cmd.append(" where name='");sql_cmd.append(book_name);sql_cmd.append("'");                break;default:cout<<"不存在 "<<op_code<<" 对应的查询方式，查询失败"<<endl;return ;}cout<<"query cmd : "<<sql_cmd<<endl;// 初始化SQL            sql_loader_init();// 创建并构造sql语句，用完后手动删除             stmt = con->createStatement();try{// 执行查询res = stmt->executeQuery(sql_cmd);while (res->next()) {/* Access column data by alias or column name */cout << res->getInt("id") << res->getString("name") << res->getString("author") << res->getInt("quantity") << endl;book_list.push_back(Book(res->getString("name"), res->getString("author"), res->getInt("price"), res->getInt("quantity"), res->getInt("id")));/* Access column data by numeric offset, 1 is the first column *///cout << res->getString(1) << endl;}// 资源释放delete res;delete stmt;} catch (sql::SQLException &e) {cout << "# ERR: SQLException in " << __FILE__;cout << "(" << __FUNCTION__ << ") on line "<< __LINE__ << endl;cout << "# ERR: " << e.what();cout << " (MySQL error code: " << e.getErrorCode();cout << ", SQLState: " << e.getSQLState() << " )" << endl;}return ;}private:sql_loader(){}
};

Makefile，编译路径根据实际路径做调整。

default:g++ -std=c++11 -I /data/home/code/github/cpp-test/mysql/include/jdbc -L /data/home/code/github/cpp-test/mysql/lib64   library_main.cpp -o app  -lmysqlcppconn
clean:rm -rf app

3. 创建数据库

// 创建数据库
create database library;    // 创建图书表
create table books (id int not null auto_increment,name varchar(1024) not null,author   varchar(1024) not null,price int not null default 0,quantity int not null default 1,primary key(id)
)DEFAULT CHARACTER SET = utf8;

4. 可能遇到的编译问题解决方案

1. jdbc/mysql_connection.h:37:32: fatal error: boost/shared_ptr.hpp: No such file or directory

解决方式是安装boost-devel，yum安装命令如下，ubuntu或者其它平台请自行搜索。

yum install boost-devel

2. # ERR: Host '127.0.0.1' is not allowed to connect to this MySQL server (MySQL error code: 1130, SQLState: HY000 )

无法连接MySQL，先查看本地msyqld是否允许以及能否登陆，都正常可能是权限问题，参考这篇博客：

https://blog.csdn.net/eric_sunah/article/details/18567091

参考文档：

1. https://docs.oracle.com/cd/E17952_01/connector-cpp-1.1-en