PHP object-oriented work unit example explanation

namespace woo\domain;

//标识映射
class ObjectWatcher{
  
  private $all = array();        //存放对象的小仓库
  private $dirty = array();      //存放需要在数据库中修改的对象
  private $new = array();        //存放需要在数据库中新增的对象
  private $delete = array();      //存放需要在数据库中删除的对象
  private static $instance;      //单例
  
  
  private function __construct (){}
  
  static function instance(){
    if(!self::$instance){
      self::$instance = new ObjectWatcher();
    }
    return self::$instance;
  }
  
  //获取一个唯一的标识,这里采用了领域类类名+ID的方式创建一个唯一标识，避免多个数据库表调用这个类时出现ID重复的问题
  function globalKey(DomainObject $obj){
    $key = get_class($obj) . "." . $obj->getId();
    return $key;
  }
  
  //添加对象
  static function add(DomainObject $obj){
    $inst = self::instance();
    $inst->all[$inst->globalKey($obj)] = $obj;
  }
  
  //获取对象
  static function exists($classname,$id){
    $inst = self::instance();
    $key = "$classname.$id";
    if(isset($inst->all[$key]){
      return $inst->all[$key];
    }
    return null;
  }
  
  //标记为需要删除的对象
  static function addDelete(DomainObject $obj){
    $self = self::instance();
    $self->delete[$self->globalKey($obj)] = $obj;
  }
  
  //标记为需要修改的对象
  static function addDirty(DomainObject $obj){
    $inst = self::instance();
    if(!in_array($obj,$inst->new,true)){
      $inst->dirty[$inst->globalKey($obj)] = $obj;
    }
  }
  
  //标记为需要新增的对象
  static function addNew(DomainObject $obj){
    $inst = self::instance();
    $inst->new[] = $obj;
  }
  
  //标记为干净的对象
  static function addClean(DomainObject $obj){
    $self = self::instance();
    unset($self->delete[$self->globalKey($obj)]);
    unset($self->dirty[$self->globalKey($obj)]);
    $self->new = array_filter($self->new,function($a) use($obj) {return !($a === $obj);});
  }
    
  //将上述需要增删改的对象与数据库交互进行处理  
  function performOperations(){
    foreach($this->dirty as $key=>$obj){
      $obj->finder()->update($obj);    //$obj->finder()获取一个数据映射器
    }
    foreach($this->new as $key=>$obj){
      $obj->finder()->insert($obj);
    }
    $this->dirty = array();
    $this->new = array();
  }
}


//领域模型
abstract class DomainObject{      //抽象基类
  
  private $id = -1;
  
  function __construct ($id=null){
    if(is_null($id)){
      $this->markNew();      //初始化时即被标记为需要新增的对象了
    } else {
      $this->id = $id;
    }  
  }
  
  //调用了标识映射的标记对象的方法
  function markNew(){
    ObjectWatcher::addNew($this);
  }
  
  function markDeleted(){
    ObjectWatcher::addDelete($this);
  }
  
  function markDirty(){
    ObjectWatcher::addDirty($this);
  }
  
  function markClean(){
    ObjectWatcher::addClean($this);
  }
  
  function setId($id){
    $this->id = $id;
  }
  
  function getId(){
    return $this->id;
  }
  
  
  function finder(){
    return self::getFinder(get_class($this));
  }
  
  //通过工厂类来实例化一个特定类型的数据映射器对象，例如VenueMapper
  //这个对象将被标识映射器中的performOperations方法调用用于与数据库交互进行增删改的操作
  static function getFinder($type){
    return HelperFactory::getFinder($type);
  }
  
}


class Venue extends DomainObject {
  private $name;
  private $spaces;
  
  function __construct ($id = null,$name=null){
    $this->name= $name;
    $this->spaces = self::getCollection('\\woo\\domain\\space'); 
    parent::__construct($id);
  }
  
  function setSpaces(SpaceCollection $spaces){
    $this->spaces = $spaces;
    $this->markDirty();            //标记为需要修改的对象
  }
  
  function addSpace(Space $space){
    $this->spaces->add($space);
    $space->setVenue($this);
    $this->markDirty();            //标记为需要修改的对象
  }
  
  function setName($name_s){
    $this->name = $name_s;
    $this->markDirty();            //标记为需要修改的对象
  }
  
  function getName(){
    return $this->name;
  }
}


//领域模型
class Space extends DomainObject{
  //.........
  function setName($name_s){
    $this->name = $name_s;
    $this->markDirty();
  }
  
  function setVenue(Venue $venue){
    $this->venue = $venue;
    $this->markDirty();
  }
}


//数据映射器
abstract class Mapper{
  
  abstract static $PDO;    //操作数据库的pdo对象
  function __construct (){
    if(!isset(self::$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);
    }
  }
  
  //获取标记的对象
  private function getFroMap($id){
    return \woo\domain\ObjectWatcher::exists($this->targetClass(),$id);
  }
  
  
  //新增标记的对象
  private function addToMap(\woo\domain\DomainObject $obj){//////
    return \woo\domain\ObjectWatcher::add($obj);
  }
  
  
  //将数据库数据映射为对象
  function createObject($array){
    $old = $this->getFromMap($array['id']);
    if($old){return $old;}
    $obj = $this->doCreateObject($array);
    $this->addToMap($obj);
    $obj->markClean();
    return $obj;
  }

  
  function find($id){                //通过ID从数据库中获取一条数据并创建为对象  
    $old = $this->getFromMap($id);        
    if($old){return $old}            
    
    $this->selectStmt()->execute(array($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);          
    return $object;  
  }
  
  
  function insert(\woo\domain\DomainObject $obj){      //将对象数据插入数据库
    $this->doInsert($obj);
    $this->addToMap($obj);            
  }
  
  //需要在子类中实现的各个抽象方法
  abstract function targetClass();                    //获取类的类型
  abstract function update(\woo\domain\DomainObject $objet);        //修改操作
  protected abstract function doCreateObject(array $array);        //创建对象
  protected abstract function selectStmt();                //查询操作
  protected abstract function doInsert(\woo\domain\DomainObject $object);  //插入操作
  
}

class VenueMapper extends Mapper {
  function __construct (){    
    parent::__construct();  
    //预处理对象
    $this->selectStmt = self::$PDO->prepare("select * from venue where id=?");
    $this->updateStmt = self::$PDO->prepare("update venue set name=?,id=? where id=?");
    $this->insertStmt = self::$PDO->prepare("insert into venue (name) values(?)");
  }
  
  protected function getCollection(array $raw){    //将Space数组转换成对象集合
    return new SpaceCollection($raw,$this);        
  }
  
  protected function doCreateObject (array $array){  //创建对象
    $obj = new \woo\domain\Venue($array['id']);
    $obj->setname($array['name']);
    return $obj;
  }
  
  protected function doInsert(\woo\domain\DomainObject $object){ //将对象插入数据库
    print 'inserting';
    debug_print_backtrace();
    $values = array($object->getName());
    $this->insertStmt->execute($values);
    $id = self::$PDO->lastInsertId();
    $object->setId($id);
  }
  
  function update(\woo\domain\DomainObject $object){    //修改数据库数据
    print "updation\n";
    $values = array($object->getName(),$object->getId(),$object->getId());
    $this->updateStmt->execute($values);
  }
  
  function selectStmt(){          //返回一个预处理对象
    return $this->selectStmt;
  }
  
}


//客户端
$venue = new \woo\domain\Venue(null,"The Green Tree");        //在初始化时就被标记为新增对象了
$venue->addSpace(new \woo\domain\Space(null,"The Space Upstairs"));  //这二行addSpace方法因为venue已经被标记新增所以不会再标记为修改对象,但是space在初始化的时候会被标记为新增对象
$venue->addSpace(new \woo\domain\Space(null,"The Bar Stage"));　　　　　　
\woo\domain\ObjectWatcher::instance()->performOperations();      //与数据库交互新增一条Venue数据,以及二条space数据