介绍一个针对C++程序的MySQL访问库soci

Home

Database

Mysql Tutorial

介绍一个针对C++程序的MySQL访问库soci_MySQL

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 01, 2016 pm 01:00 PM

mysql

一直以来，笔者都在不停寻找一种更人性化的数据库访问方式（并不是说默认的方式不好，而是有时候的确在模块化设计中不太方便）。
后来有幸在php中找到codeigniter的ActiveReord，详细参考这篇文章: 抽离CodeIgniter的数据库访问类！
然而c++却始终用着最原始的方式，昨天趁着项目要用的机会，在网上搜索了好久，总算让我找到两套c++的数据库访问框架:

soci
litesql

两套代码我都拿下来看了一下，litesql实现了一套完整的代码自动生成，功能强大，但是也很重；soci相对要轻量，但是同样也实现了数据结构到数据库表的映射。本人还是比较喜欢轻量的东西，所以最终选择了soci。经过这两天的试用，感觉非常不错。

官方的文档也很详细，所以这里就用我写的单元测试代码来做一下简单的讲解:
首先创建库表:

create database soci;
CREATE TABLE `tb_test` (
 `id` int(11) NOT NULL auto_increment,
 `name` varchar(32) default "",
 `sex` int(11) default 0,
 PRIMARY KEY (`id`),
 UNIQUE KEY `name` (`name`)
);
 
create database soci;
CREATE TABLE `tb_test` (
 `id` int(11) NOT NULL auto_increment,
 `name` varchar(32) default "",
 `sex` int(11) default 0,
 PRIMARY KEY (`id`),
 UNIQUE KEY `name` (`name`)
);

1.简单的select单条记录

TEST(soci,select_one)
{
  try
  {
    session sql(mysql, "host=localhost db=soci user=dantezhu");
    indicator ind;

    string name = "dandan";
    int sex;
    sql << "select sex from tb_test where name = :name",
      into(sex, ind), use(name);

    ASSERT_EQ(ind, i_ok) << name;
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}
 
TEST(soci,select_one)
{
  try
  {
    session sql(mysql, "host=localhost db=soci user=dantezhu");
    indicator ind;
 
    string name = "dandan";
    int sex;
    sql << "select sex from tb_test where name = :name",
      into(sex, ind), use(name);
 
    ASSERT_EQ(ind, i_ok) << name;
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}

select的结果，如果成功则ind会为i_ok，同值sex被赋值；如果失败则反之

2.简单的select多条记录

TEST(soci,select_multi2)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");
    indicator ind;

    int count;
    sql << "select count(*) from tb_test", into(count, ind);
    ASSERT_EQ(ind, i_ok) << count;

    if (count == 0)
    {
      SUCCEED();
      return;
    }

    int sex = 1;
    vector<string> vec_name(count);
    vector<int> vec_sex(count);
    sql << "select name,sex from tb_test where sex = :sex",
      into(vec_name), into(vec_sex), use(sex);
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}
 
TEST(soci,select_multi2)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");
    indicator ind;
 
    int count;
    sql << "select count(*) from tb_test", into(count, ind);
    ASSERT_EQ(ind, i_ok) << count;
 
    if (count == 0)
    {
      SUCCEED();
      return;
    }
 
    int sex = 1;
    vector<string> vec_name(count);
    vector<int> vec_sex(count);
    sql << "select name,sex from tb_test where sex = :sex",
      into(vec_name), into(vec_sex), use(sex);
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}

与select单条记录唯一的区别即，into()的参数是一个vector。其实用多个vector这种方式并不是一个很好的选择，后面会介绍基于数据结构的方式。

3.简单的insert

TEST(soci,insert_exist)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");

    string name = "dandan";
    int sex = 1;

    sql << "insert into tb_test(name, sex) values(:name, :sex)",
      use(name), use(sex);
  }
  catch (exception const &e)
  {
    SUCCEED()<<e.what();
  }
}
 
TEST(soci,insert_exist)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");
 
    string name = "dandan";
    int sex = 1;
 
    sql << "insert into tb_test(name, sex) values(:name, :sex)",
      use(name), use(sex);
  }
  catch (exception const &e)
  {
    SUCCEED()<<e.what();
  }
}

insert，update，delete都有两个同样的问题:
a)affect_rows(操作的行数)没有办法返回
b)操作的id无法知道，尤其对于insert的主键是自增的情况下，无法知道插入的主键的值是多少。

update和delete都与insert相似，这里就不再多说。

接下来是这个框架的很重要的一个特性，即数据库表与数据结构绑定：

首先我们需要定义一个结构体，并告知soci怎么让列名和数据结构的字段对应起来:

struct Person
{
  int id;
  std::string name;
  int sex;
};

namespace soci
{
  template<> struct type_conversion<Person>
  {
    typedef values base_type;
    static void from_base(values const & v, indicator /* ind */, Person & p)
    {
      p.id = v.get<int>("id");
      p.name = v.get<std::string>("name");
      p.sex = v.get<int>("sex");
    }
    static void to_base(const Person & p, values & v, indicator & ind)
    {
      v.set("id", p.id);
      v.set("name", p.name);
      v.set("sex", p.sex);
      ind = i_ok;
    }
  };
}
 
struct Person
{
  int id;
  std::string name;
  int sex;
};
 
namespace soci
{
  template<> struct type_conversion<Person>
  {
    typedef values base_type;
    static void from_base(values const & v, indicator /* ind */, Person & p)
    {
      p.id = v.get<int>("id");
      p.name = v.get<std::string>("name");
      p.sex = v.get<int>("sex");
    }
    static void to_base(const Person & p, values & v, indicator & ind)
    {
      v.set("id", p.id);
      v.set("name", p.name);
      v.set("sex", p.sex);
      ind = i_ok;
    }
  };
}

关于

template<> struct type_conversion<Person>
 
template<> struct type_conversion<Person>

这里，官方的文档是是有误的，我查了好长时间，按照上面的写法来写即可。

1.用数据结构来select

TEST(soci,select_obj_one)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");
    indicator ind;

    int count;
    sql << "select count(*) from tb_test", into(count, ind);
    ASSERT_EQ(ind, i_ok) << count;

    string name = "dandan";
    Person p;
    sql << "select id,name,sex from tb_test where name = :name",
      into(p, ind), use(name);

    ASSERT_EQ(ind, i_ok) << name;

    if (sql.got_data())
    {
      cout<< p.id 
        << "," 
        << p.name 
        << "," 
        << p.sex 
        << endl;
    }

  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}
 
TEST(soci,select_obj_one)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");
    indicator ind;
 
    int count;
    sql << "select count(*) from tb_test", into(count, ind);
    ASSERT_EQ(ind, i_ok) << count;
 
    string name = "dandan";
    Person p;
    sql << "select id,name,sex from tb_test where name = :name",
      into(p, ind), use(name);
 
    ASSERT_EQ(ind, i_ok) << name;
 
    if (sql.got_data())
    {
      cout<< p.id 
        << "," 
        << p.name 
        << "," 
        << p.sex 
        << endl;
    }
 
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}

2.用数据结构来进行insert

TEST(soci,insert_obj_noexist)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");

    Person p = {
      0,
      "niuniu",
      2
    };

    sql << "insert into tb_test(name, sex) values(:name, :sex)",
      use(p);
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}
 
TEST(soci,insert_obj_noexist)
{
  try
  {
    session sql(mysql, "db=soci user=dantezhu");
 
    Person p = {
      0,
      "niuniu",
      2
    };
 
    sql << "insert into tb_test(name, sex) values(:name, :sex)",
      use(p);
  }
  catch (exception const &e)
  {
    FAIL()<<e.what();
  }
}

整个就是这样~~下面是文中代码文件的下载路径：
http://code.google.com/p/vimercode/source/browse/#svn%2Ftrunk%2Fsoci_test

另外，虽然python下的mysql访问也算比较简单，但还是想知道是否有更Pythonic的库或接口，如果有朋友知道，欢迎不吝告知。

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn