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 = $dbh->prepare('SELECT name, colour, caloriesFROM fruitWHERE calories < ? AND colour = ?');$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 $sql = 'SELECT name, colour, caloriesFROM fruitWHERE calories < :calories AND colour = :colour';$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 $this->_dbh->lastInsertId();}}?>
数据映相关类射类，使用__call达到动态生成getter 和setter方法.
<?php/*** 抽象数据映射**/abstractclass Table{public function __call($method, $args) {if (preg_match('/^(get|set)(\w+)/', strtolower($method), $match)&& $attribute = $this->validateAttribute($match)) {if ('get' == $match) {return $this->$attribute;} else {$this->$attribute = $args;}}else {throw new Exception('Call to undefined method ' . __CLASS__. '::'.$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';publicstatic $tablefileds = array('uid','username','level','exp','ctime','mtime',);/*** 对象生成数组** @return array*/function toArray(){$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 userWHERE uid=:uid ";const DELETE_SQL = "delete from userWHERE 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) : $userTable;}}?>
实际客户测试：
<?php/*** 数据库配置文件**/define('BACKEND_DBHOST', 'localhost');define('BACKEND_DBUSER', 'root');define('BACKEND_DBPW', '123456');define('BACKEND_DBNAME', 'sample');define('BACKEND_DBCHARSET', 'utf-8');//sql/*CREATE TABLE IF NOT EXISTS `user` (`uid` int(11) NOT NULL AUTO_INCREMENT,`username` varchar(64) NOT NULL,`level` int(11) NOT NULL DEFAULT '0',`exp` int(11) NOT NULL DEFAULT '0',`ctime` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',`mtime` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',PRIMARY KEY (`uid`),KEY `username` (`username`)) ENGINE=InnoDBDEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ;*/class client{static function main(){$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
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