学步园

使用java中的动态代理可以完成很多事情，比如将业务实例进行托管，实现AOP等，但是Php中没有实现这样的东西，昨天突然想到其实可以通过eval来模拟一个动态代理机制。php比java不同的是，php是不需要编译的，因此只要我们能够动态生成一段代码，然后用eval来执行就可以达到效果。代码如下：

/**<br /> * 代理实现类<br /> */<br /> interface IInvocationHandler<br /> {<br /> function invoke($method, array $arr_args);<br /> }<br /> /**<br /> * 代理类<br /> */<br /> final class Proxy<br /> {<br /> const CLASS_TEMPLATE = '<br /> final class %s implements %s<br /> {<br /> private $handler;<br /> public function __construct(IInvocationHandler $handler)<br /> {<br /> $this->handler = $handler;<br /> }<br /> %s<br /> }<br /> ';<br /> const FUNCTION_TEMPLATE = '<br /> public function %s(%s)<br /> {<br /> $arr_args = func_get_args ();<br /> $arr_method = explode("::", __METHOD__);<br /> $this->handler->invoke ( $arr_method[1], $arr_args );<br /> }<br /> ';<br /> public static function newProxyInstance(array $arr_interface, IInvocationHandler $handler)<br /> {<br /> $className = self::getClassName ( $arr_interface );<br /> if (class_exists ( $className ))<br /> {<br /> return new $className ( $handler );<br /> }<br /> self::checkInterfaceExists ( $arr_interface );<br /> self::generateClass ( $arr_interface );<br /> return new $className ( $handler );<br /> }<br /> protected static function generateClass(array $arr_interface)<br /> {<br /> $className = self::getClassName ( $arr_interface );<br /> $interfaceList = implode ( ',', $arr_interface );<br /> $functionList = '';<br /> foreach ( $arr_interface as $interface )<br /> {<br /> $class = new ReflectionClass ( $interface );<br /> $arr_method = $class->getMethods ();<br /> foreach ( $arr_method as $method )<br /> {<br /> $methodName = $method->getName ();<br /> $arr_parameter = $method->getParameters ();<br /> $parameterArray = array ();<br /> foreach ( $arr_parameter as $parameter )<br /> {<br /> $parameterName = $parameter->getName ();<br /> $parameterArray [] = '$' . $parameterName;<br /> }<br /> $parameterList = implode ( ',', $parameterArray );<br /> }<br /> $functionList .= sprintf ( self::FUNCTION_TEMPLATE, $methodName, $parameterList );<br /> }<br /> $code = sprintf ( self::CLASS_TEMPLATE, $className, $interfaceList, $functionList );<br /> eval ( $code );<br /> }<br /> protected static function checkInterfaceExists(array $arr_interface)<br /> {<br /> foreach ( $arr_interface as $interface )<br /> {<br /> if (! interface_exists ( $interface ))<br /> {<br /> throw new Exception ( "interface $interface do not loaded" );<br /> }<br /> }<br /> }<br /> protected static function getClassName(array $arr_interface)<br /> {<br /> return 'Class_' . implode ( '_', $arr_interface ) . '_Implementation';<br /> }<br /> }<br /> class Test implements ITest1, ITest2<br /> {<br /> /**<br /> * @see ITest1::test1()<br /> *<br /> * @param unknown_type $arg1<br /> * @param unknown_type $arg2<br /> */<br /> function test1($arg1, $arg2)<br /> {<br /> echo "Test::test1($arg1, $arg2)/n";<br /> return "ok";<br /> }<br /> /**<br /> * @see ITest2::test2()<br /> *<br /> */<br /> function test2()<br /> {<br /> echo "Test::test2()/n";<br /> return "failed";<br /> }<br /> }<br /> class Target implements IInvocationHandler<br /> {<br /> private $target;<br /> public function __construct()<br /> {<br /> $this->target = new Test ( );<br /> }<br /> /**<br /> * @see IInvocationHandler::invoke()<br /> *<br /> * @param ReflectionMethod $method<br /> * @param array $arr_args<br /> */<br /> function invoke($methodName, array $arr_args)<br /> {<br /> $method = new ReflectionMethod ( 'Test', $methodName );<br /> echo "before call method $methodName/n";<br /> $ret = $method->invokeArgs ( $this->target, $arr_args );<br /> echo "after call method $methodName return $ret/n";<br /> return $ret;<br /> }<br /> }<br /> interface ITest1<br /> {<br /> function test1($arg1, $arg2);<br /> }<br /> interface ITest2<br /> {<br /> function test2();<br /> }<br /> $proxy = Proxy::newProxyInstance ( array ('ITest1', 'ITest2' ), new Target ( ) );<br /> $proxy->test2 ();<br /> $proxy = Proxy::newProxyInstance ( array ('ITest1' ), new Target ( ) );<br /> $proxy->test1 ( 'a', 1 );

其实从这个例子可以推出来，我们甚至可以模拟asm的相关功能，而且实现要比java简单很多。看来以前没有挖掘php的功能呀，这个语言被我低估了。