thinkphp5源码解析(1)数据库
前言
tp5的数据库操作全部通过Db类完成,比较符合国人的习惯,比如简单的Db::query()、Db::execute(),还有复杂的链式操作Db::table('user')->where('id=1')->select(),下面就通过源码来了解其工作流程
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看代码之前,先看看涉及到的类都有哪些,tp5的数据库相关的类有以下几个:
Db(用户接口)
Connection(连接器)
Query(查询器)
Builder(SQL生成器)
Db::query()发生了什么?
假定配置文件设置驱动为MySQL,当执行以下代码时,tp5的数据库类是怎么工作的?
Db::query("select * from user where id=?", [1]);
为了节省篇章以及更好地理解流程,下面只展示核心代码,部分代码被简化或改造,我们来看看Db类:
class Db { private static $instance = []; private static function parseConfig($config) { if (empty($config)) { $config = Config::get('database'); } else { $config = Config::get($config); } return $config; } public static function connect($config = []) { $name = md5(serialize($config)); if (!isset(self::$instance[$name])) { $options = self::parseConfig($config); self::$instance[$name] = new \think\db\connector\Mysql($options); } return self::$instance[$name]; } public static function __callStatic($method, $params) { return call_user_func_array([self::connect(), $method], $params); } }
因为Db类没有定义query(),所以触发了__callStatic(),__callStatic()又调用自身的connect(),connect()实例化Mysql连接器(传入数据库配置$options),然后保存到$instance(数据库连接实例数组),再来看看Mysql连接器:
namespace think\db\connector; class Mysql extends Connection { protected $builder = '\\think\\db\\builder\\Mysql'; }
Mysql连接器也没有定义query()呀,它继承了Connection,看看Connection有没有:
abstract class Connection { protected $PDOStatement; protected $linkID; protected $config = []; public function __construct(array $config = []) { if (!empty($config)) { $this->config = array_merge($this->config, $config); } } protected function getResult() { return $this->PDOStatement->fetchAll(PDO::FETCH_ASSOC); } protected function bindValue(array $bind = []) { foreach ($bind as $key => $val) { $param = is_numeric($key) ? $key + 1 : ':' . $key; if (is_array($val)) { if (PDO::PARAM_INT == $val[1] && '' === $val[0]) { $val[0] = 0; } $result = $this->PDOStatement->bindValue($param, $val[0], $val[1]); } else { $result = $this->PDOStatement->bindValue($param, $val); } } } public function connect() { if (!$this->linkID) { $config = $this->config; $this->linkID = new PDO($config['dsn'], $config['username'], $config['password']); } return $this->linkID; } public function query($sql, $bind = []) { $this->connect(); if (empty($this->PDOStatement)) { $this->PDOStatement = $this->linkID->prepare($sql); } $this->bindValue($bind); $this->PDOStatement->execute(); return $this->getResult(); } }
结论
Db::query()触发Db::__callStatic(),实例化Mysql连接器并调用Mysql->query(),而Mysql连接器继承了Connection,所以实际上是调用了Connection->query()
Db::table('user')->where('id=1')->select()发生了什么?
Db和Mysql连接器都没有定义table()方法,发现Connection也有个__call():
protected function getQuery() { return new \think\db\Query($this); } public function __call($method, $args) { return call_user_func_array([$this->getQuery(), $method], $args); }
所以Db::table('user')实际上是触发了__call()魔术方法,然后实例化了一个Query对象(构造函数传入当前Mysql连接器对象),看看Query里面做了什么:
namespace think\db; class Query { protected $connection; protected $builder; public function __construct(Connection $connection) { $this->connection = $connection; $this->setBuilder(); } protected function setBuilder() { $this->builder = new \think\db\builder\Mysql($this->connection, $this); } public function table($table) { $this->options['table'] = $table; return $this; } public function where($where) { $this->options['where'] = $where; return $this; } public function query($sql) { return $this->connection->query($sql); } public function select() { $options = $this->options; $this->options = []; $sql = $this->builder->select($options);return $this->query($sql); } }
首先构造函数保存了当前的Mysql连接器对象,并实例化think\db\builder\Mysql
Query->table()把表名保存到$options数组,然后返回$this(当前实例)从而实现链式操作,where()同样,重点看看select(),它拿到$options之后把它清空以便下次使用,然后调用了Builder->select()拿到拼装好的sql,交由Connection->query()查询数据库获得结果集,整个流程到此结束,那么Builder是怎么拼装sql的呢?
namespace think\db\builder; class Mysql extends Builder { protected function parseRand() { return 'rand()'; } }
think\db\builder\Mysql并没有定义select(),不过它继承了Builder,看看Builder代码:
namespace think\db; abstract class Builder { protected $connection; protected $query; protected $selectSql = 'SELECT %FIELD% FROM %TABLE% %WHERE%'; public function select($options = []) { $sql = str_replace( ['%TABLE%', '%FIELD%', '%WHERE%'], [ $options['table'], $options['field'] ?: '*', $options['where'] ? 'WHERE'.$options['where'] : '', ], $this->selectSql); return $sql; } }
Builder通过$options替换sql模板拿到sql
结论
Db::table()触发了__callStatic()实例化Connection并调用table(),由于Connection也没有定义table(),又触发了自身的__call()实例化Query并调用table(),table()返回$this实现链式操作DB::table()->where()->select(),而select又调用Builder->select()拿到sql,最终调用Connection->query()获取查询结果,固完整的类图表示如下:
名称栏目:thinkphp5源码解析(1)数据库
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