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This article mainly introduces the relevant knowledge of how to use Netty in Java, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this Java article on how to use Netty. Let's take a look at it.

I. brief introduction

The underlying API of Java is becoming more and more complex, and the requirements of development scenarios faced by developers are also increasing. If you program directly against the underlying API, it is undoubtedly time-consuming and labor-consuming. This gives rise to a large number of programming frameworks that hide the complex details of API implementation and provide developers with functional implementation interfaces in the most concise way. Netty is a framework for web links, and its emergence allows server developers to focus more on the implementation of more logic, rather than headaches for better, more and more stable links. The core function of Netty is based on NIO.

Second, the application scenario of Netty

It is suitable for almost all long and short link scenarios, and almost all Internet companies will use it more or less because of the universality of Java applications. Bloggers are engaged in game development, it can be said that almost all short-link game servers are developed using Netty. Servers with high effectiveness and hot repair requirements generally do not use Java. At present, most of them are combined with C+Lua. The fact that Java cannot be hotfixed is an important reason why many long-chain servers do not consider java.

III. Asynchronous and event-driven

As emphasized in the NIO article, the main features of this model are async and event-driven, where the server does not have to wait for link input until the link is closed. Instead, you can go to the input of the link at a specific time, which is another event-driven. When the link changes, an event will be generated, and after the NIO model detects this event, it will deal with the event accordingly.

IV. Core components of Netty

1.Channel:

Channel is a basic construct of Java-NIO, which represents open links to an entity, such as read and write operations, and can also be understood as an inbound or outbound data carrier in the NIO model, which can be closed or closed.

two。 Callback ChannelHandler:

A callback is a method. Netty provides two subclasses, ChannelInboundHandlerAdapter and ChannelOutboundHandlerAdapter. These two subclasses can be applied to data inbound and outbound, respectively. Callbacks at various stages, such as the inbound Active method, indicate that the link has just been established. The code is as follows:

Public class ConnectHandler extend ChannelInboundHandlerAdapter {@ override public void ChannelActive (ChannelHandlerContext ctx) {/ / data inbound callback subclass is called when the link is established, that is, System.out.println is called when the link is established ("remote client:" + ctx.channel (). RemoteAddress () + 'establish link');}}

Readers who don't know Netty may be a little confused about how this class should be used. Here's a simple explanation: this class registers into the service when Netty is created, and then calls different callback functions in this class at different stages of inbound and outbound data to deal with different development requirements. You can follow the reader's other articles.

3.Future:

An implementation of Future is provided in jdk-Future:Java, and this Futrue can be seen as a placeholder for the result of an asynchronous operation. We can query the result of this asynchronous operation through this Future and do some processing. For example, throw an exception when an operation fails. However, jdk's built-in Future query can only query the results manually at some point, or block the asynchronous operation directly until the success or failure of the Future can be queried after the asynchronous operation is completed.

In the Future implementation class provided within ChannelFuture:Netty, many asynchronous operations will return a ChannelFuture object when executed. We can set some callback functions for this ChannelFuture object, such as overriding the operationComplete () method, so that this asynchronous event will automatically call this method when it is completed and execute our own processing logic.

Next, you can take a look at the application example of ChannelFuture to check whether the remote address of the Netty server is successful:

Channel channel = ""; / / Port 7000 of the link address 192.168.100.113 InetSocketAddress socketAddress = new InetSocketAddress ("192.168.100.113", 7000); / / the pipe binds the address and returns a ChannelFutureChannelFuture channelFuture = channel.connect (socketAddress) / / set the completion callback to ChannelFuture to determine whether the operation completes channelFuture.addListener (new ChannelFutureListener () {@ override public void operationComplete (ChannelFuture future) {if (future.isSucess ()) {/ / create a string and specify the character set to be used. The following is ByteBuf buffer = Unpooled.copiedBuffer ("Hello", Charset.defaultCharset ()) that is often encountered in Netty. / / send a message and return a new writeFuture. You can still handle some logic ChannelFuture writeFuture = future.channel () .writeAndFlush (buffer) according to this writeFuture. } else {/ / if the link fails, the message Throwable cause = future.cause (); cause.printStackTrace () is allowed. }}) this is the end of the article on "how to use Netty in Java". Thank you for reading! I believe you all have a certain understanding of "how to use Netty in Java". If you want to learn more, you are welcome to follow the industry information channel.

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