thinkphp5源码解析(1)数据库

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：

<?php
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();
        
    }
    
}

这就很明确了，Connection定义了query()，它调用connect()执行pdo驱动连接数据库，然后进行数据绑定，最后获取查询结果

结论

Db并没有实现query()，它只负责实例化对应的数据库驱动，通过__callStatic()魔术方法调用Connection的query()，UML类图表示：

 

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think\db\Query对象（构造函数传入当前think\db\connector\Mysql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think\db\connector\Mysql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think\db\builder\Mysql->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think\db\builder\Mysql是怎么拼装sql的呢？

namespace think\db\builder;

class Mysql extends Builder
{
    protected function parseRand()
    {
        return ‘rand()‘;
    }
}

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：

thinkphp5源码解析(1)数据库

标签：驱动   结束   没有   serial   sele   ons   类图   fetch   field