适配器模式

将某个对象的接口适配为另一个对象所期望的接口,例如某个操作数据库的有多种不同的数据库操作方法,通过适配器统一成一个接口

目录结构

|adpater  #项目根目录
|--Think  #核心类库
|----Database  #数据库操作类
|------MySQLAdapter.php  #MySQL类
|------MySQLiAdapter.php  #MySQLi类
|------PDOAdapter.php  #PDO类
|----Loder.php  #自动加载类
|----Target.php  #数据库适配器接口类
|----DataBase.php  #统一的数据库类
|--index.php #单一的入口文件

代码实现

数据库适配器接口类 Think/Target.php

<?php
namespace Think;

//定义一个数据库的适配器接口类
interface Target{
    function connect($host, $user, $passwd, $dbname);
    function query($sql);
    function close();
}

MySQLAdapter类 Think/Database/MySQLAdapter.php

<?php
namespace Think\Database;
use Think\Target;

class MySQLAdapter implements Target{
    protected $conn;  //用于存放连接数据库句柄

    //实现连接方法
    public function connect($host, $user, $passwd, $dbname) {
        $conn = mysql_connect($host, $user, $passwd);
        mysql_select_db($dbname, $conn);
        $this->conn = $conn;
    }

    //查询方法
    public function query($sql) {
        $res = mysql_query($sql, $this->conn);
        return $res;
    }

    //关闭方法
    public function close() {
        mysql_close($this->conn);
    }
}

MySQLiAdapter类 Think/Database/MySQLiAdapter.php

<?php
namespace Think\Database;
use Think\Target;

class MySQLiAdapter implements Target{
    protected $conn; //用于存放连接数据库句柄

    //实现连接方法
    public function connect($host, $user, $passwd, $dbname) {
        $conn = mysqli_connect($host, $user, $passwd, $dbname);
        $this->conn = $conn;
    }

    //查询方法
    public function query($sql) {
        $res = mysqli_query($this->conn , $sql);
        return $res;
    }

    //关闭方法
    public function close() {
        mysqli_close($this->conn);
    }
}

PDOAdapter类 Think/Database/PDOAdapter.php

<?php
namespace Think\Database;
use Think\Target;

class PDOAdapter implements Target{
    protected $conn;  //用于存放连接数据库句柄

    //实现连接方法
    public function connect($host, $user, $passwd, $dbname) {
        $conn = new \PDO("mysql:host={$host}; dbname={$dbname}", $user, $passwd);
        $this->conn = $conn;
    }

    //查询方法
    public function query($sql) {
        return $this->conn->query($sql);
    }

    //关闭方法
    public function close() {
        unset($this->conn);
    }
}

统一的数据库类 Think/DataBase.php

<?php
namespace Think;

class DataBase implements Target{
    protected $db;  //存放数据库对象

    //设置数据库类
    public function __construct($type = '') {
        $type = "\\Think\\Database\\".$type;
        $this->db = new $type;
    }

    //链接数据库
    public function connect($host, $user, $passwd, $dbname) {
        $this->db->connect($host, $user, $passwd, $dbname);
    }

    //查询方法
    public function query($sql) {
        return $this->db->query($sql);
    }

    //关闭连接
    public function close() {
        $this->db->close();
    }
}

自动加载 Think/Loder.php

<?php
namespace Think;

class Loder{
    static function autoload($class){
        require BASEDIR . '/' .str_replace('\\','/',$class) . '.php';
    }
}

入口文件 index.php

<?php
define('BASEDIR',__DIR__);
include BASEDIR . '/Think/Loder.php';
spl_autoload_register('\\Think\\Loder::autoload');

$db = new \Think\DataBase('MySQLiAdapter');
$db->connect('localhost','root','123456','test');

print_r($db);