【IT168 技术文档】本文介绍了JAVA事件模式的PHP实现。在我以前的文章里,我概括了系统事件定义和使用call_user_func()函数建立php 事件模块的例子。本文通过引入高级的基于sender/eventObject/listener的php事件模块对这个科目进行了扩展。
下面是一个JAVA 事件系统的例子。这个例子基于Apache小组 开发的,来源于Apache.org并进行了重新缩短和重顶格式后的 ProtocolCommandSupport.java, ProtocolCommandListener.java and ProtocolCommandEvent.java文件。ProtocolCommandSupport.java文件包含了事件创建类,类的实例由系统创建,当系统被实例调用时,就就会创建该事件。事实上这个类看上去就像包含了一个监听器---类监听到事件创建并且在事件创建被通知时进行反应。注意 “addProtocolCommandListener” and “removeProtocolCommandListener”方法,他们用于附加和分离监听。另外2个方法fireCommandSent” and “fireReplyReceived”,召唤了对象“__listeners” 容器储存的方法。该容器实际上,只积累了ProtocolCommandListener 对象,因为只有该对象在调用addProtocolCommandListener” and “removeProtocolCommandListener”方法时能够被通过。
ProtocolCommandSupport.java
public class ProtocolCommandSupport implements Serializable {
private Object __source;
private ListenerList __listeners = new ListenerList();
public ProtocolCommandSupport(Object source) {
__source = source;
}
/***
* Fires a ProtocolCommandEvent signalling the sending of a command to all
* registered listeners.
***/
public void fireCommandSent(String command, String message) {
Enumeration en = __listeners.getListeners();
ProtocolCommandEvent event =
new ProtocolCommandEvent(__source, command, message);
ProtocolCommandListener listener;
while (en.hasMoreElements()) {
listener = (ProtocolCommandListener)en.nextElement();
listener.protocolCommandSent(event);
}
}
/***
* Fires a ProtocolCommandEvent signalling the reception of a command reply
* to all registered listeners.
***/
public void fireReplyReceived(int replyCode, String message) {
Enumeration en = __listeners.getListeners();
ProtocolCommandEvent event =
new ProtocolCommandEvent(__source, replyCode, message);
ProtocolCommandListener listener;
while (en.hasMoreElements()) {
listener = (ProtocolCommandListener)en.nextElement();
listener.protocolReplyReceived(event);
}
}
public void addProtocolCommandListener(ProtocolCommandListener listener) {
__listeners.addListener(listener);
}
public void removeProtocolCommandListener(ProtocolCommandListener listener) {
__listeners.removeListener(listener);
}
}
ProtocolCommandListener.java 包含了监听器接口。其后的含义是任何将要由ProtocolCommandSupport类认证的事件将要提供这个能够实现一个足够被事件认证接口。这就可能造成了一个新的种类,2个或更多不同的类被事件认证,因为一个类能够实现多重接口。
ProtocolCommandListener.java
public interface ProtocolCommandListener extends EventListener {
/***
* This method is invoked by a ProtocolCommandEvent source after
* sending a protocol command to a server.
*
* @param event The ProtocolCommandEvent fired.
***/
public void protocolCommandSent(ProtocolCommandEvent event);
/***
* This method is invoked by a ProtocolCommandEvent source after
* receiving a reply from a server.
*
* @param event The ProtocolCommandEvent fired.
***/
public void protocolReplyReceived(ProtocolCommandEvent event);
}
本文的最后一个文件是ProtocolCommandEvent.java。这个文件包含了一个EventObject 类中的叫做ProtocolCommandEvent的子集。EventObject的子集用于通过从event producer到event listeners的事件数据。ProtocolCommandEvent 类增加了一个定义在EventObject中的getSource()方法,创建了creates the getMessage(), isReply(), isCommand(), getReplyCode() and getCommand()方法。这些方法只能返回给类一个只读字段,只能在构造函数中设置。
ProtocolCommandEvent.java
public class ProtocolCommandEvent extends EventObject {
private int __replyCode;
private boolean __isCommand;
private String __message, __command;
public ProtocolCommandEvent(Object source, String command, String message) {
super(source);
__replyCode = 0;
__message = message;
__isCommand = true;
__command = command;
}
public ProtocolCommandEvent(Object source, int replyCode, String message) {
super(source);
__replyCode = replyCode;
__message = message;
__isCommand = false;
__command = null;
}
public String getCommand() { return __command; }
public int getReplyCode() { return __replyCode; }
public boolean isCommand() { return __isCommand; }
public boolean isReply() { return !isCommand(); }
public String getMessage() { return __message; }
}
这3个文件组,只是JAVA事件系统的普通实现。也许把它应用于PHP程序是一个好的尝试。