CompletableFuture和netty

CompletableFuture是Java 8中引入的一个类，继承了java.util.concurrent.Future接口，它是一种可完成的Future。相比传统的Future，CompletableFuture能够主动设置计算的结果值，从而在某些场景下主动结束阻塞等待。而传统的Future只有在计算结果产生或超时时才会返回。

Netty是一个基于异步事件驱动的网络应用框架，它使用了CompletableFuture来实现异步调用。Netty提供了自己的Future接口，它继承了java.util.concurrent.Future接口，并且扩展了一些重要的方法，比如isSuccess()、addListener()和removeListener()等。

通过使用CompletableFuture和Netty的异步策略，我们可以实现从同步调用到异步调用的转换。使用CompletableFuture的主动设置结果值的特性，结合Netty的异步事件驱动机制，我们可以实现高效的异步编程。

相关问题

jar rpc netty框架代码

以下是一个基于Netty框架的RPC实现示例代码：

1. 服务接口定义

public interface HelloService {
    String sayHello(String name);
}

2. 服务提供者实现

public class HelloServiceImpl implements HelloService {
    public String sayHello(String name) {
        return "Hello, " + name;
    }
}

3. RPC框架实现

public class RpcServer {
    private final EventLoopGroup bossGroup;
    private final EventLoopGroup workerGroup;

    public RpcServer() {
        bossGroup = new NioEventLoopGroup();
        workerGroup = new NioEventLoopGroup();
    }

    public void start(int port) throws InterruptedException {
        ServerBootstrap b = new ServerBootstrap();
        b.group(bossGroup, workerGroup)
         .channel(NioServerSocketChannel.class)
         .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            public void initChannel(SocketChannel ch) throws Exception {
                ChannelPipeline p = ch.pipeline();
                p.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
                p.addLast(new ObjectEncoder());
                p.addLast(new RpcServerHandler());
            }
         })
         .option(ChannelOption.SO_BACKLOG, 128)
         .childOption(ChannelOption.SO_KEEPALIVE, true);

        ChannelFuture f = b.bind(port).sync();
        System.out.println("Server started on port " + port);
        f.channel().closeFuture().sync();
    }

    public void shutdown() {
        workerGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();
    }
}

public class RpcServerHandler extends ChannelInboundHandlerAdapter {
    private static final Map<String, Object> serviceMap = new ConcurrentHashMap<>();

    static {
        serviceMap.put(HelloService.class.getName(), new HelloServiceImpl());
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof RpcRequest) {
            RpcRequest request = (RpcRequest) msg;
            Object service = serviceMap.get(request.getClassName());
            if (service != null) {
                Method method = service.getClass().getMethod(request.getMethodName(), request.getParameterTypes());
                Object result = method.invoke(service, request.getParameters());
                RpcResponse response = new RpcResponse();
                response.setRequestId(request.getRequestId());
                response.setResult(result);
                ctx.writeAndFlush(response);
            }
        } else {
            super.channelRead(ctx, msg);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }
}

4. RPC客户端实现

public class RpcClient {
    private final EventLoopGroup group;
    private final Bootstrap bootstrap;

    public RpcClient() {
        group = new NioEventLoopGroup();
        bootstrap = new Bootstrap();
        bootstrap.group(group)
                 .channel(NioSocketChannel.class)
                 .option(ChannelOption.TCP_NODELAY, true)
                 .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    public void initChannel(SocketChannel ch) throws Exception {
                        ChannelPipeline p = ch.pipeline();
                        p.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
                        p.addLast(new ObjectEncoder());
                        p.addLast(new RpcClientHandler());
                    }
                 });
    }

    public void connect(String host, int port) throws InterruptedException {
        ChannelFuture future = bootstrap.connect(host, port).sync();
        future.channel().closeFuture().sync();
    }

    public void shutdown() {
        group.shutdownGracefully();
    }
}

public class RpcClientHandler extends ChannelInboundHandlerAdapter {
    private final Map<String, RpcFuture> pendingRequests = new ConcurrentHashMap<>();

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof RpcResponse) {
            RpcResponse response = (RpcResponse) msg;
            RpcFuture future = pendingRequests.get(response.getRequestId());
            if (future != null) {
                pendingRequests.remove(response.getRequestId());
                future.done(response.getResult());
            }
        } else {
            super.channelRead(ctx, msg);
        }
    }

    public RpcFuture sendRequest(RpcRequest request) {
        RpcFuture future = new RpcFuture(request);
        pendingRequests.put(request.getRequestId(), future);
        ctx.writeAndFlush(request);
        return future;
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }
}

public class RpcFuture {
    private final RpcRequest request;
    private final CompletableFuture<Object> responseFuture;

    public RpcFuture(RpcRequest request) {
        this.request = request;
        responseFuture = new CompletableFuture<>();
    }

    public void done(Object result) {
        responseFuture.complete(result);
    }

    public CompletableFuture<Object> getResponseFuture() {
        return responseFuture;
    }

    public RpcRequest getRequest() {
        return request;
    }
}

5. RPC请求/响应实体类定义

public class RpcRequest implements Serializable {
    private String requestId;
    private String className;
    private String methodName;
    private Class<?>[] parameterTypes;
    private Object[] parameters;

    // getters and setters
}

public class RpcResponse implements Serializable {
    private String requestId;
    private Object result;

    // getters and setters
}

使用示例：

// 启动服务端
RpcServer server = new RpcServer();
server.start(8080);

// 创建客户端
RpcClient client = new RpcClient();
client.connect("localhost", 8080);

// 发送请求
RpcRequest request = new RpcRequest();
request.setRequestId(UUID.randomUUID().toString());
request.setClassName(HelloService.class.getName());
request.setMethodName("sayHello");
request.setParameterTypes(new Class[] { String.class });
request.setParameters(new Object[] { "World" });
RpcFuture future = client.sendRequest(request);

// 处理响应
future.getResponseFuture().thenAccept(result -> {
    System.out.println(result);
});

// 关闭客户端和服务端
client.shutdown();
server.shutdown();

https://blog.csdn.net/myyhtw/article/details/94579126，根据这个网页，springboot netty tcp通信，创建10000个客户端，连接服务器，优化代码

这篇博客讲述了如何利用Spring Boot框架结合Netty实现TCP通信，同时处理大量并发连接的情况，比如创建10000个客户端。首先，作者介绍了Spring Boot作为应用启动器的优势，并提到Netty是一个高性能、异步事件驱动的网络应用程序框架。

以下是博主提供的优化点和步骤：

1. **批量初始化客户端连接**：为了减少单次连接创建的开销，可以一次性创建所有客户端连接，然后逐个分配给需要的线程池任务，而不是在每个请求时都创建新的连接。

List<Future<Void>> futures = new ArrayList<>();
for (int i = 0; i < 10000; i++) {
    ChannelInitializer<?> init = ... // 初始化器
    EventLoopGroup group = ... // 客户端EventLoopGroup
    FutureChannel future = group.newChannel(init);
    futures.add(future);
}

CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();

2. **使用异步处理**：通过Netty的`EventExecutorGroup`或`SelectorManager`管理并发任务，让每个客户端请求在独立的线程上执行，提高响应速度。

3. **负载均衡和连接复用**：考虑配置连接池，如`NioEventLoopGroup`下的`Bootstrap`，以便重用已经建立的连接，避免频繁地创建和销毁连接。

4. **性能监控**：使用Spring Boot的Actuator模块或其他工具对性能进行监控，识别瓶颈并进行调整。

5. **内存管理**：注意控制内存泄漏，特别是在关闭连接后及时释放资源，可以使用Netty的`channel_inactive()`回调或自定义处理器进行清理。