PHP學(xué)習(xí)
namespace woo\domain;
//標(biāo)識(shí)映射類
class ObjectWatcher{
  
  private $all = array();        //存放對象的小倉庫
  private static $instance;      //單例
  
  private function __construct (){}
  
  static function instance(){
    if(!self::$instance){
      self::$instance = new ObjectWatcher();
    }
    return self::$instance;
  }
  
  //獲取一個(gè)唯一的標(biāo)識(shí),這里采用了領(lǐng)域類類名+ID的方式創(chuàng)建一個(gè)唯一標(biāo)識(shí),避免多個(gè)數(shù)據(jù)庫表調(diào)用這個(gè)類時(shí)出現(xiàn)ID重復(fù)的問題
  function globalKey(DomainObject $obj){
    $key = get_class($obj) . "." . $obj->getId();
    return $key;
  }
  
  //添加對象
  static function add(DomainObject $obj){
    $inst = self::instance();
    $inst->all[$inst->globalKey($obj)] = $obj;
  }
  
  //獲取對象
  static function exists($classname,$id){
    $inst = self::instance();
    $key = "$classname.$id";
    if(isset($inst->all[$key]){
      return $inst->all[$key];
    }
    return null;
  }
}
namespace woo\mapper;
abstract class Mapper{      //抽象基類
  abstract static $PDO;    //操作數(shù)據(jù)庫的pdo對象
  function __construct (){
    if(!isset(self::$PDO){
      $dsn = \woo\base\ApplicationRegistry::getDSN();
      if(is_null($dsn)){
        throw new \woo\base\AppException("no dns");
      }
      self::$PDO = new \PDO($dsn);
      self::$PDO->setAttribute(\PDO::ATTR_ERRMODE,\PDO::ERRMODE_EXCEPTION);
    }
  }
  
  //數(shù)據(jù)映射器基礎(chǔ)上新增的方法以下會(huì)簡稱新增,這里的作用的是獲取對象而不是查詢數(shù)據(jù)庫并重復(fù)創(chuàng)建對象
  //(對比一下原數(shù)據(jù)映射器的相關(guān)代碼即可了解)
  private function getFroMap($id){
    return \woo\domain\ObjectWatcher::exists($this->targetClass(),$id);
  }
  
  //新增,這里的作用的是將創(chuàng)建的對象保存起來
  private function addToMap(\woo\domain\DomainObject $obj){//////
    return \woo\domain\ObjectWatcher::add($obj);
  }
  
  
  //對比原數(shù)據(jù)映射器的代碼,便發(fā)現(xiàn)它不是直接創(chuàng)建對象而是首先在標(biāo)識(shí)映射類中查找,找不到才調(diào)用的
  //子類的方法創(chuàng)建并插入到標(biāo)識(shí)映射類,下面的find方法也遵循了這一原則
  function createObject($array){          
    $old = $this->getFromMap($array['id']);  //新增
    if($old){return $old}          //新增
    $obj = $this->doCreateObject($array);  //在子類中實(shí)現(xiàn)
    $this->addToMap($obj);          //新增
    return $obj;
  }
  
  //
  function find($id){                //通過ID從數(shù)據(jù)庫中獲取一條數(shù)據(jù)并創(chuàng)建為對象  
    $old = $this->getFromMap($id);        //新增
    if($old){return $old}            //新增
    
    $this->selectStmt()->execute(array($id));
    $array= $this->selectStmt()->fetch();
    $this->selectStmt()->closeCursor();
    if(!is_array($array)){
      return null;
    }
    if(!isset($array['id'])){
      return null;
    }
    $object = $this->createObject($array);
    $this->addToMap($object);          //新增
    return $object;  
  }
  
  function insert(\woo\domain\DomainObject $obj){      //將對象數(shù)據(jù)插入數(shù)據(jù)庫
    $this->doInsert($obj);
    $this->addToMap($obj);            //新增
  }
  
  //需要在子類中實(shí)現(xiàn)的各抽象方法
  abstract function targetClass();//////
  abstract function update(\woo\domain\DomainObject $objet);
  protected abstract function doCreateObject(array $array);
  protected abstract function selectStmt();
  protected abstract function doInsert(\woo\domain\DomainObject $object);
}
class SpaceMapper extends Mapper {
  //其他代碼在數(shù)據(jù)映射器一文中已有實(shí)現(xiàn)這里略過
  //.............
  
  //類名,在標(biāo)識(shí)映射類中生成唯一標(biāo)識(shí)用的
  protected function targetClass(){
    return "woo\\domain\\Space";
  }
}