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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:

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 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

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 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

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 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

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 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:

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 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

? 1 2 3 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

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 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

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 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。