laravel框架model类查询实现：
User::where(['uid'=8])->get();
User类继承自Model类：IlluminateDatabaseEloquentModel
当User类静态调用where方法时，自动调用了Model里的魔术方法：
public static function __callStatic($method, $parameters){ $instance = new static; //这里的$instance就是User类的实例对象 return call_user_func_array([$instance, $method], $parameters);}相当于调用了user对象的where方法，这时就又调用了魔术方法：
public function __call($method, $parameters){ if (in_array($method, ['increment', 'decrement'])) { return call_user_func_array([$this, $method], $parameters); } $query = $this->newQuery(); //返回IlluminateDatabaseEloquentBuilder对象 return call_user_func_array([$query, $method], $parameters);}相当于调用IlluminateDatabaseEloquentBuilder对象里的where方法和get方法，这两个方法里其实
其实是封装调用了IlluminateDatabaseQueryBuilder对象里的where方法和get方法->get方法里调用了runselect方法
runSelect方法:
/** * Run the query as a "select" statement against the connection. * * @return array */protected function runSelect(){ return $this->connection->select($this->toSql(), $this->getBindings(), ! $this->useWritePdo); //调用connection 对象的select方法}再看connection对象是怎么传到IlluminateDatabaseEloquentBuilder类实例里的：
Model类的newQuery方法：
/** * Get a new query builder for the model's table. * * @return IlluminateDatabaseEloquentBuilder */public function newQuery(){ $builder = $this->newQueryWithoutScopes(); return $this->applyGlobalScopes($builder);}Model类的newQueryWithoutScopes方法：
/** * Get a new query builder that doesn't have any global scopes. * * @return IlluminateDatabaseEloquentBuilder|static */public function newQueryWithoutScopes(){ $builder = $this->newEloquentBuilder( $this->newBaseQueryBuilder() //这个方法返回 ); // Once we have the query builders, we will set the model instances so the // builder can easily access any information it may need from the model // while it is constructing and executing various queries against it. return $builder->setModel($this)->with($this->with);}Model类的newBaseQueryBuilder方法实现
/** * Get a new query builder instance for the connection. * * @return IlluminateDatabaseQueryBuilder */protected function newBaseQueryBuilder(){ $conn = $this->getConnection(); 连接数据库并返回connection对象 $grammar = $conn->getQueryGrammar(); return new QueryBuilder($conn, $grammar, $conn->getPostProcessor()); //IlluminateDatabaseQueryBuilder}Model类的$resolver属性(连接解析器)的设定是通过
IlluminateDatabaseDatabaseServiceProvider 里的boot方法设置的
这样Model类的getConnection方法实际调用的DatabaseManager类的connection方法，返回connection类实例
如何创建的数据库连接：
Model类getConnection方法->DatabaseManager类connection方法->
->ConnectionFactory类的createSingleConnection()
/** * Create a single database connection instance. * * @param array $config * @return IlluminateDatabaseConnection */protected function createSingleConnection(array $config){ //创建连接器对象并连接数据库返回pdo对象 $pdo = $this->createConnector($config)->connect($config); //传入PDO对象、并返回connection对象，connection对象负责查询数据库 return $this->createConnection($config['driver'], $pdo, $config['database'], $config['prefix'], $config); }
