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。