【活动记录的意图】
一个对象，它包装数据表或视图中某一行，封装数据库访问，并在这些数据上增加了领域逻辑。
【活动记录的适用场景】
适用于不太复杂的领域逻辑，如CRUD操作等。
【活动记录的运行机制】
对象既有数据又有行为。其使用最直接的方法，将数据访问逻辑置于领域对象中。
活动记录的本质是一个领域模型，这个领域模型中的类和基数据库中的记录结构应该完全匹配，类的每个域对应表的每一列。
一般来说，活动记录包括如下一些方法：
1、由数据行构造一个活动记录实例;
2、为将来对表的插入构造一个新的实例;
3、用静态查找方法来包装常用的SQL查询和返回活动记录;
4、更新数据库并将活动记录中的数据插入数据库;
5、获取或设置域;
6、实现部分业务逻辑。
【活动记录的优点和缺点】
优点：
1、简单，容易创建并且容易理解。
2、在使用事务脚本时，减少代码复制。
3、可以在改变数据库结构时不改变领域逻辑。
4、基于单个活动记录的派生和测试验证会很有效。
缺点：
1、没有隐藏关系数据库的存在。
2、仅当活动记录对象和数据库中表直接对应时，活动记录才会有效。
3、要求对象的设计和数据库的设计紧耦合，这使得项目中的进一步重构很困难
【活动记录与其它模式】
数据源架构模式之行数据入口：活动记录与行数据入口十分类似。二者的主要差别是行数据入口 仅有数据库访问而活动记录既有数据源逻辑又有领域逻辑。
【活动记录的PHP示例】
<ol class="dp-c">
<li class="alt"><span><span><?php </span></span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="comment">/** </span> </li>
<li><span><span class="comment"> * 企业应用架构 数据源架构模式之活动记录 2010-10-17 sz </span> </span></li>
<li class="alt"><span><span class="comment"> * @author phppan.p#gmail.com http://www.phppan.com </span> </span></li>
<li><span><span class="comment"> * 哥学社成员（http://www.blog-brother.com/） </span> </span></li>
<li class="alt"><span><span class="comment"> * @package architecture </span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">/** </span> </li>
<li class="alt"><span><span class="comment"> * 定单类 </span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt">
<span class="keyword">class</span><span> Order { </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 定单ID </span> </span></li>
<li class="alt"><span><span class="comment"> * @var <type> </type></span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt">
<span> </span><span class="keyword">private</span><span> </span><span class="vars">$_order_id</span><span>; </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 客户ID </span> </span></li>
<li class="alt"><span><span class="comment"> * @var <type> </type></span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt">
<span> </span><span class="keyword">private</span><span> </span><span class="vars">$_customer_id</span><span>; </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 定单金额 </span> </span></li>
<li class="alt"><span><span class="comment"> * @var <type> </type></span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt">
<span> </span><span class="keyword">private</span><span> </span><span class="vars">$_amount</span><span>; </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> __construct(</span><span class="vars">$order_id</span><span>, </span><span class="vars">$customer_id</span><span>, </span><span class="vars">$amount</span><span>) { </span>
</li>
<li>
<span> </span><span class="vars">$this</span><span>->_order_id = </span><span class="vars">$order_id</span><span>; </span>
</li>
<li class="alt">
<span> </span><span class="vars">$this</span><span>->_customer_id = </span><span class="vars">$customer_id</span><span>; </span>
</li>
<li>
<span> </span><span class="vars">$this</span><span>->_amount = </span><span class="vars">$amount</span><span>; </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 实例的删除操作 </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> </span><span class="func">delete</span><span>() { </span>
</li>
<li class="alt">
<span> </span><span class="vars">$sql</span><span> = </span><span class="string">"DELETE FROM Order SET WHERE order_id = "</span><span> . </span><span class="vars">$this</span><span>->_order_id . </span><span class="string">" AND customer_id = "</span><span> . </span><span class="vars">$this</span><span>->_customer_id; </span>
</li>
<li>
<span> </span><span class="keyword">return</span><span> DB::query(</span><span class="vars">$sql</span><span>); </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 实例的更新操作 </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> update() { </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 插入操作 </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> insert() { </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> load(</span><span class="vars">$rs</span><span>) { </span>
</li>
<li>
<span> </span><span class="keyword">return</span><span> </span><span class="keyword">new</span><span> Order(</span><span class="vars">$rs</span><span>[</span><span class="string">'order_id'</span><span>] ? </span><span class="vars">$rs</span><span>[</span><span class="string">'order_id'</span><span>] : NULL, </span><span class="vars">$rs</span><span>[</span><span class="string">'customer_id'</span><span>], </span><span class="vars">$rs</span><span>[</span><span class="string">'amount'</span><span>] ? </span><span class="vars">$rs</span><span>[</span><span class="string">'amount'</span><span>] : 0); </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">class</span><span> Customer { </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="keyword">private</span><span> </span><span class="vars">$_name</span><span>; </span>
</li>
<li>
<span> </span><span class="keyword">private</span><span> </span><span class="vars">$_customer_id</span><span>; </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> __construct(</span><span class="vars">$customer_id</span><span>, </span><span class="vars">$name</span><span>) { </span>
</li>
<li class="alt">
<span> </span><span class="vars">$this</span><span>->_customer_id = </span><span class="vars">$customer_id</span><span>; </span>
</li>
<li>
<span> </span><span class="vars">$this</span><span>->_name = </span><span class="vars">$name</span><span>; </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 用户删除定单操作 此实例方法包含了业务逻辑 </span> </span></li>
<li class="alt"><span><span class="comment"> * 通过调用定单实例实现 </span> </span></li>
<li><span><span class="comment"> * 假设此处是对应的删除操作（实际中可能是一种以某字段来标记的假删除操作） </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> deleteOrder(</span><span class="vars">$order_id</span><span>) { </span>
</li>
<li class="alt">
<span> </span><span class="vars">$order</span><span> = Order::load(</span><span class="keyword">array</span><span>(</span><span class="string">'order_id'</span><span> => </span><span class="vars">$order_id</span><span>, </span><span class="string">'customer_id'</span><span> => </span><span class="vars">$this</span><span>->_customer_id)); </span>
</li>
<li>
<span> </span><span class="keyword">return</span><span> </span><span class="vars">$order</span><span>-></span><span class="func">delete</span><span>(); </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 实例的更新操作 </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> update() { </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * 入口类自身拥有插入操作 </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> insert() { </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> load(</span><span class="vars">$rs</span><span>) { </span>
</li>
<li>
<span> </span><span class="comment">/* 此处可加上缓存 */</span><span> </span>
</li>
<li class="alt">
<span> </span><span class="keyword">return</span><span> </span><span class="keyword">new</span><span> Customer(</span><span class="vars">$rs</span><span>[</span><span class="string">'customer_id'</span><span>] ? </span><span class="vars">$rs</span><span>[</span><span class="string">'customer_id'</span><span>] : NULL, </span><span class="vars">$rs</span><span>[</span><span class="string">'name'</span><span>]); </span>
</li>
<li><span> } </span></li>
<li class="alt"><span> </span></li>
<li>
<span> </span><span class="comment">/** </span> </li>
<li class="alt"><span><span class="comment"> * 根据客户ID 查找 </span> </span></li>
<li><span><span class="comment"> * @param integer $id 客户ID </span> </span></li>
<li class="alt"><span><span class="comment"> * @return Customer 客户对象 </span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt">
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> find(</span><span class="vars">$id</span><span>) { </span>
</li>
<li>
<span> </span><span class="keyword">return</span><span> CustomerFinder::find(</span><span class="vars">$id</span><span>); </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt">
<span class="comment">/** </span> </li>
<li><span><span class="comment"> * 人员查找类 </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span class="keyword">class</span><span> CustomerFinder { </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> find(</span><span class="vars">$id</span><span>) { </span>
</li>
<li class="alt">
<span> </span><span class="vars">$sql</span><span> = </span><span class="string">"SELECT * FROM person WHERE customer_id = "</span><span> . </span><span class="vars">$id</span><span>; </span>
</li>
<li>
<span> </span><span class="vars">$rs</span><span> = DB::query(</span><span class="vars">$sql</span><span>); </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span> </span><span class="keyword">return</span><span> Customer::load(</span><span class="vars">$rs</span><span>); </span>
</li>
<li class="alt"><span> } </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="keyword">class</span><span> DB { </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span> </span><span class="comment">/** </span> </li>
<li class="alt"><span><span class="comment"> * 这只是一个执行SQL的演示方法 </span> </span></li>
<li><span><span class="comment"> * @param string $sql 需要执行的SQL </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> query(</span><span class="vars">$sql</span><span>) { </span>
</li>
<li class="alt">
<span> </span><span class="func">echo</span><span> </span><span class="string">"执行SQL: "</span><span>, </span><span class="vars">$sql</span><span>, </span><span class="string">" <br>"</span><span>; </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="keyword">if</span><span> (</span><span class="func">strpos</span><span>(</span><span class="vars">$sql</span><span>, </span><span class="string">'SELECT'</span><span>) !== FALSE) { </span><span class="comment">// 示例，对于select查询返回查询结果 </span><span> </span>
</li>
<li>
<span> </span><span class="keyword">return</span><span> </span><span class="keyword">array</span><span>(</span><span class="string">'customer_id'</span><span> => 1, </span><span class="string">'name'</span><span> => </span><span class="string">'Martin'</span><span>); </span>
</li>
<li class="alt"><span> } </span></li>
<li><span> } </span></li>
<li class="alt"><span> </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">/** </span> </li>
<li class="alt"><span><span class="comment"> * 客户端调用 </span> </span></li>
<li><span><span class="comment"> */</span><span> </span></span></li>
<li class="alt">
<span class="keyword">class</span><span> Client { </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/** </span> </li>
<li><span><span class="comment"> * Main program. </span> </span></li>
<li class="alt"><span><span class="comment"> */</span><span> </span></span></li>
<li>
<span> </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> main() { </span>
</li>
<li class="alt"><span> </span></li>
<li><span> </span></li>
<li class="alt">
<span> header(</span><span class="string">"Content-type:text/html; charset=utf-8"</span><span>); </span>
</li>
<li><span> </span></li>
<li class="alt">
<span> </span><span class="comment">/* 加载客户ID为1的客户信息 */</span><span> </span>
</li>
<li>
<span> </span><span class="vars">$customer</span><span> = Customer::find(1); </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span> </span><span class="comment">/* 假设用户拥有的定单id为 9527*/</span><span> </span>
</li>
<li class="alt">
<span> </span><span class="vars">$customer</span><span>->deleteOrder(9527); </span>
</li>
<li><span> } </span></li>
<li class="alt"><span> </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li><span>Client::main(); </span></li>
<li class="alt"><span>?> </span></li>
</ol>同前面的文章一样，这仅仅是一个活动记录的示例，关于活动记录模式的应用，可以查看Yii框架中的DB类，在其源码中有一个CActiveRecord抽象类，从这里可以看到活动记录模式的应用
另外，如果从事务脚本中创建活动记录，一般是首先将表包装为入口，接着开始行为迁移，使表深化成为活动记录。
对于活动记录中的域的访问和设置可以如yii框架一样，使用魔术方法__set方法和__get方法。
