php 设计模式数据映射模式（应用程序与数据库交互模式）

前面提到的设计模式大大提高了代码的可读性与可维护性。然而，在WEB应用设计与开发中一个基本的需求与挑战：数据库应用，这些设计模式都没有涉及到。数据映射模式使您能更好的组织你的应用程序与数据库进行交互。

下面我将用实际代码说明，如果一个表发生变动。我们要修改客户端代码就可以了。特别是游戏项目，需求经常可能会经常变动。修改表结构，可能引起大片代码的改动。

首先我们使用pdo进行数据库访问：

<?php
/**
 * Filename:db.class.php
 * 
 * db class ,use PDO lib
 * 
 * @author guisu.huang
 * @version 1.0
 * 
 */
class Db {
	public static $db = null;
	private $_dbh = null;
	public static function getInstance()
	{
		if( self::$db == null ){
			self::$db = new self(BACKEND_DBHOST ,BACKEND_DBUSER ,BACKEND_DBPW ,BACKEND_DBNAME);
		}
		return self::$db;

	}

	private function __construct( $host ,$user ,$pass ,$dbname ){
		try {
			$this->_dbh = new PDO('mysql:dbname='.$dbname.';host='.$host,$user,$pass);
			$this->_dbh->query('SET NAMES '. BACKEND_DBCHARSET);
			$this->_dbh->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
			$this->_dbh->setAttribute(PDO::ATTR_ERRMODE, true);
		} catch (PDOException $e) {
			throw new Exception('Can not connect db');
		}
	}

	private function getExecuteResult($sql, $sth){
		$type = strtolower(substr(trim($sql), 0,6));
		switch ($type) {
			case 'update': case 'delete':
				$result = $sth->rowcount();//返回影响的行数
			break;
			case 'insert':
				$result = $this->getLastId();
				break;
			case 'select':
				$result = $sth->fetchAll(PDO::FETCH_ASSOC);
				break;
			default:
				break;
		}
		return $result;
	}
	
	/**************************************sql ************************/
	
	public function getOne($sql){
		try {
			$rs = $this->_dbh->query($sql);
			$result = $rs->fetch(PDO::FETCH_ASSOC);
			if(!empty($result)) {
				return $result;
			}
		} catch (PDOException $e) {
			throw new Exception($this->_dbh->errorInfo());
		}
		return false;
	}

	public function getAll($sql){
		try {
			$rs = $this->_dbh->query($sql);
			$result = $rs->fetchAll(PDO::FETCH_ASSOC);
			if(!empty($result)) {
				return $result;
			}
		} catch (PDOException $e) {
			throw new Exception($this->_dbh->errorInfo());
		}
		return false;
	}

	public function exec($sql){
		try {
			$exec = $this->_dbh->exec($sql);
		} catch (PDOException $e){
			throw new Exception($this->_dbh->errorInfo());
		}
		return $exec;

	}
	/**
	 * 不关注键值
	 *  Execute a prepared statement by passing an array of values 
		$sth = $dbh->prepare('SELECT name, colour, calories
		    FROM fruit
		    WHERE calories < ? AND colour = ?');
		$sth->execute(array(150, 'red'));
		$red = $sth->fetchAll();
		$sth->execute(array(175, 'yellow'));
		$yellow = $sth->fetchAll();

	 * @param unknown_type $sql
	 * @param unknown_type $arr
	 * @return unknown
	 */
	public function executeArr($sql, $arr){
		try {
			$sth = $this->_dbh->prepare($sql);
			$r = $sth->execute($arr);
			if ($r) {
				return  $this->getExecuteResult($sql, $sth);
			}
		} catch (PDOException $e){
			throw new Exception($e->getMessage() . $this->_dbh->errorInfo());
		}	
	}
	/**
	 * 关联数组:
	 *  Execute a prepared statement by passing an array of values 
			$sql = 'SELECT name, colour, calories
		    FROM fruit
		    WHERE calories < :calories AND colour = :colour';
		$sth = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY));
		$sth->execute(array(':calories' => 150, ':colour' => 'red'));
		$red = $sth->fetchAll();
	 *
	 * @param unknown_type $sql
	 * @param unknown_type $arr
	 * @return unknown
	 */
	public function executeAsoc($sql, $arr){
		try {
			$array = array();
			if ($arr) {
				foreach ($arr as $key=>$v) {
					if (strpos($sql, ':' . $key )!==false) {
						$array[':' . $key] = $v;
					}
				}
			}
			$sth = $this->_dbh->prepare($sql);
			$r = $sth->execute($array);
			if ($r) {
				return  $this->getExecuteResult($sql, $sth);
			}
		} catch (PDOException $e){
			throw new Exception($e->getMessage() . $this->_dbh->errorInfo());
		}	
	}
	
	public function beginTransaction(){
		return $this->_dbh->beginTransaction();
	}

	public function commit(){
		return $this->_dbh->commit();
	}

	public function rollBack(){
		return $this->_dbh->rollBack();
	}

	public function getLastId()
	{
		return $this->_dbh->lastInsertId();
	}

	
	
}

?>

数据映相关类射类，使用__call达到动态生成getter 和setter方法.

<?php
/**
 * 抽象数据映射
 *
 */
abstract  class Table{

	public function __call($method, $args) {
		if (preg_match('/^(get|set)(\w+)/', strtolower($method), $match)
		&& $attribute = $this->validateAttribute($match[2])) {
			if ('get' == $match[1]) {
				return $this->$attribute;
			} else {
				$this->$attribute = $args[0];
			}
		}else {
			throw new Exception(
			'Call to undefined method ' . __CLASS__  . '::'.$method.'()');
		}
	}

	protected function validateAttribute($method) {
		if ( in_array(strtolower($method), array_keys(get_class_vars(get_class($this))))) {
			return strtolower($method);
		}

	}
	
	
}

/**
 * 数据映射到表
 * 一般根据表的结构由工具自动生成，
 * 要不然程序员经常得copy和修改这个类
 *
 */
class UserTable extends Table {
	/**
	 * fields
	 *
	 * @var unknown_type
	 */
	protected $uid = null;

	protected $username = null ;

	protected $level = null;

	protected $exp = null;

	protected $ctime = null;

	protected $mtime = null;
	/**
	 * table 
	 *
	 * @var unknown_type
	 */
	public   $tableName = 'user';

	public  $primaryKey = 'uid';
	
	public  static $tablefileds = array(
						'uid',
						'username',
						'level',
						'exp',
						'ctime',
						'mtime',
	);
	
	/**
	 * 对象生成数组
	 *
	 * @return array
	 */
	function toArray(){
		$arr = array();
		foreach (UserTable::$tablefileds as $filed) {
			$getMethod  = 'get' .ucwords($filed);
			$value = $this->$getMethod();
			if ($value !== null) {
				$arr[$filed] = $value;
			}
		}
		return $arr;
	}
	
	/**
	 * 数组生成对象
	 *
	 * @return array
	 */
	function toObj($arr){
		if (!$arr) {
			return $this;
		}
		foreach (UserTable::$tablefileds as $filed) {
			$setMethod  = 'set' .ucwords($filed);
			$this->$setMethod($arr[$filed]);
		}
		return $this;
	}
}

/**
 * 
 *
 */
class Mapper{
	
	protected  $conn = null;
	
	/**
	 * 自动插入
	 * 不想对某一列插入，把对应的属性设置成null就ok
	 *
	 * @param Table $table
	 * @return unknown
	 */
	function save(Table $table){
		$arr  =  $table->toArray();
		$set = '';
		if ($arr) {
			foreach ($arr as $field=> $v) {
				if ($set) $set .=',';
				$set .= $field . "='" . $v ."'";
			}
		}
		if ($set) {
			$this->conn->exec( 'insert into ' . $table->tableName . ' SET ' . $set);
			return $this->conn->getLastId();
		}
		
		
	}
	
	/**
	 * 更新
	 * 不想对某一列更新，把对应的属性设置成null就ok
	 *
	 * @param Table $table
	 * @return unknown
	 */
	function update(Table $table){
		$arr  =  $table->toArray();
		$set = '';
		if ($arr) {
			foreach ($arr as $field=> $v) {
				if ($set) $set .=',';
				$set .= $field . "='" . $v ."'";
			}
		}
		$primayGet = 'get'.ucwords($table->primaryKey);
		if ($set) {
			return $this->conn->exec( 'update ' . $table->tableName . ' SET ' . $set . ' where ' . $table->primaryKey ."='" . $table->$primayGet() . "'" );
		}
	}

	
}
class UserMapper extends Mapper {
	
	const INSERT_SQL = "insert into user (username, level,exp, ctime, mtime) values (:username, :level, :exp, now(), now())";
	const UPDATE_SQL = "update user SET username=:username, level=:level, exp=:exp WHERE uid=:uid ";
	const SELECT_SQL = "select * from user  WHERE uid=:uid ";
	const DELETE_SQL = "delete from user  WHERE uid=:uid ";
	
	function __construct(){
		$this->conn =  Db::getInstance();
	}
	/**
	 * 我们可以实现覆盖save
	 *
	 * @param unknown_type $userTable
	 */
	public function save2($userTable) {
		$rs =  Db::getInstance()->executeArr( self::INSERT_SQL, $userTable->toArray());
		return $rs;
	}
	
	/**
	 * Enter description here...
	 *
	 * @param unknown_type $userTable
	 */
	public function update2($userTable) {
		return $this->conn->execute(self::UPDATE_SQL, $userTable->toArray());
	}
	
	/**
	 * Enter description here...
	 *
	 * @param unknown_type $arr
	 */
	public function find($userTable) {
		$rs = $this->conn->executeAsoc( self::SELECT_SQL, $userTable->toArray());
		return $rs ? $userTable->toObj($rs[0]) : $userTable;
	}
}


?>

实际客户测试：

<?php

/**
 * 数据库配置文件
 *
 */
define('BACKEND_DBHOST', 'localhost');
define('BACKEND_DBUSER', 'root');
define('BACKEND_DBPW', '123456');
define('BACKEND_DBNAME', 'sample');
define('BACKEND_DBCHARSET', 'utf-8');

//sql
/*
CREATE TABLE IF NOT EXISTS `user` (
  `uid` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(64) NOT NULL,
  `level` int(11) NOT NULL DEFAULT '0',
  `exp` int(11) NOT NULL DEFAULT '0',
  `ctime` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  `mtime` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`uid`),
  KEY `username` (`username`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ;
*/

class client{
	static function main(){
		$userMapper = new UserMapper();
		$user = new UserTable();
		//插入
		//$user->setUserName('guisu');
		//$user->setLevel(1);
		//$user->setExp(10);
		//
		//$userMapper = new UserMapper();
		//$r = $userMapper->save($user);
		
		//查找
		$user->setUid(10);
		$user = $userMapper->find($user);
		var_dump($user);
		//更新
		$user->setUserName('guisu2');
		$r = $userMapper->update($user);
		var_dump($r);
	}
	
}

一般，client是业务逻辑层，UserMapper是数据访问层。UserTable底层数据结构。

我们尽量做到如果表User修改了：

1）工具重新自动生成UserTable类

2）只修改client代码和少量的UserMapper代码，一般修改UserMapper的常量const的内容就可以了。

说明转载最好说明出处：php 设计模式-数据映射模式（应用程序与数据库交互模式）http://blog.csdn.net/hguisu/article/details/7569968