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 {

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/***
* 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; }

}