问题描述
我主要是在那里与Netty,但一个概念仍然暗示我,我在教程中找不到任何东西,等等。首先我明白Netty是异步的,但是客户端必须有一种方法来调用服务器,并且能够在处理程序之外获得响应。让我解释更多。
I'm mostly there with Netty but one concept is still alluding me, and I can't find anything in the tutorials and so on. Firstly I do understand that Netty is asynchronous, but there must be a way for a client to call the server and be able to get a response beyond the handler. Let me explain more.
我有一个客户如下图所示。请注意,我理解它是自举的,每次调用都建立了一个新的连接,这只是为了使示例更小,更简洁。请忽略该事实。
I have a client as illustrated below. And please note that I understand it's bootstrapped and a new connection is established on each call, that's just there to make the example smaller and more succinct. Please ignore that fact.
Client.java
Client.java
// ServerResponse is a result from the server, in this case
// a list of users of the system (ignore that each time it's all bootstrapped).
public User[] callServerForInformationFromGUIWidget()
{
ClientBootstrap bootstrap = new ClientBootstrap(...);
bootstrap.setPipelineFactory(...);
ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));
Channel channel = future.awaitUninterruptibly().getChannel();
// Where request is a POJO sent to the server,
// with a request such as get me a list of users
RequestPojo request = new RequestPojo(requestUserListCommand);
ChannelFuture lastWriteFuture = channel.write(request);
if(lastWriteFuture != null)
lastWriteFuture.awaitUninterruptibly();
}
现在我明白了如何获取服务器上的数据,结果。唯一的是如何在客户端处理它?是的,clientHandler类可以执行如下操作:
Now I understand how to get the data on the server, and fire back the result. The only thing is how do I handle it on the client side? Yes the clientHandler class can do something like the following:
ClientHandler.java
ClientHandler.java
@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e)
{
User[] users = (User[])e.getMessage();
}
问题是客户端代码如何获得结果?所有示例都类似于聊天服务,其中事件触发了客户端上不等待响应的其他事情。甚至http客户端示例,我发现缺乏这一点。文档总体上是很好,但它缺乏如何做回调。无论如何,在这种情况下,我需要客户端从服务器获取响应,并基于结果,它会做它需要的。
The problem is how does the client code actually get that result? All the examples are similar to a chat service, where the event fires off something else on the client that's not waiting on a response. Even the http client example I found lacking this. The documentation overall is really good, but it's lacking on how to do callbacks. Anyways, in this case I need the client to get the response from the server, and based on the results it will do what it needs.
换句话说,我如何写客户端来做这样的事情:
In other words, how do I write the client to do something like this:
IdealClient.java
IdealClient.java
// ServerResponse is a result from the server, in this case
// a list of users of the system.
public User[] callServerForInformationFromGUIWidget()
{
...
RequestPojo request = new RequestPojo(requestUserListCommand);
ChannelFuture lastWriteFuture = channel.write(request);
if(lastWriteFuture != null)
lastWriteFuture.awaitUninterruptibly();
User[] users = resultFromCallToServer();
performSomeAction(users);
}
因为处理程序不知道是谁在寻找答案,问的问题。如果它是在处理程序,而不是如何做?
Because the handler doesn't know who is looking for the answer, or who asked the question. And if it's done in the handler, than how?
回到我对示例的评论,http客户端(和处理程序)示例只是将结果转储到System.out。如果你有一个GUI,你如何将结果从你的请求传递到GUI?我从来没有看到任何例子。
Back to my comments about the examples, the http client (and handler) examples just dump the result to System.out. If you had a GUI how would you pass the result from your request up to the GUI? I never saw any examples for this.
推荐答案
Jestan是正确的。在我的情况下,我有一个客户端需要处理价格tick数据。我使用Antlr进行解析。我在我的解析器中触发我的事件,但在我的case我的协议是基于字符串。下面是一个没有Antlr的例子,我传递String消息在你的情况下它可以是用户。
Jestan is correct. In my case I have a client that need to process price tick data. I use Antlr for the parsing. I fire my events in my parser, but in my case my protocol is String based. Below is an example without Antlr, I pass the String message in your case it could be the users.
//----------------- Event --------------
public class DataChangeEvent {
private String message;
public DataChangeEvent(String message) {
this.message = message;
}
public String getMessage() {
return message;
}
}
//----------------- Listener --------------
public interface DataChangeListenter {
public void dataChangeEvent(DataChangeEvent event);
}
//----------------- Event Handler that fires the dataChange events --------------
// This class needs to be static since you need to register all your classes that want to be notified of data change events
public class DataChangedHandler {
private static List<DataChangeListenter> listeners = new ArrayList<DataChangeListenter>();
public static void registerDataChangeListener(DataChangeListenter listener) {
listeners.add(listener);
}
public static void fireDataChange(DataChangeEvent dataChangeEvent) {
for(DataChangeListenter listenter : listeners) {
listenter.dataChangeEvent(dataChangeEvent);
}
}
}
//----------------- Example class that implements the listener and registers itself for events --------------
public class ProcessMessage implements DataChangeListenter {
public ProcessMessage() {
DataChangedHandler.registerDataChangeListener(this);
}
public void dataChangeEvent(DataChangeEvent event) {
//Depending on your protocal, I use Antlr to parse my message
System.out.println(event.getMessage());
}
}
//---------------- Netty Handler -----------
public class TelnetClientHandler extends SimpleChannelHandler {
private static final Logger logger = Logger.getLogger(TelnetClientHandler.class.getName());
@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
String message = (String) e.getMessage();
DataChangedHandler.fireDataChange(message);
}
}
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