Netty4.0学习笔记系列之三：构建简单的http服务

小鱼儿 2022-04-11 09:10 163阅读 0赞

本文主要介绍如何通过Netty构建一个简单的http服务。

想要实现的目的是：

1.Client向Server发送http请求。

2.Server端对http请求进行解析。

3.Server端向client发送http响应。

4.Client对http响应进行解析。

在该实例中，会涉及到http请求的编码、解码，http响应的编码、解码，幸运的是，Netty已经为我们提供了这些工具，整个实例的逻辑图如下所示：

![2a22e5d9-9a37-3204-86ee-dde07ddcd6ad.jpg][]  
        其中红色框中的4个类是Netty提供的，它们其实也是一种Handler，其中Encoder继承自ChannelOutboundHandler，Decoder继承自ChannelInboundHandler，它们的作用是：

1.HttpRequestEncoder：对httpRequest进行编码。

2.HttpRequestDecoder：把流数据解析为httpRequest。

3.HttpResponsetEncoder：对httpResponset进行编码。

4.HttpResponseEncoder：把流数据解析为httpResponse。

该实例涉及到的类有5个：HttpServer.java、HttpServerInboundHandler.java、HttpClient.java、HttpClientInboundHandler.java、ByteBufToBytes.java

1.HttpServer启动http服务器

package com.bijian.netty.server;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.ChannelOption;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.SocketChannel;
    import io.netty.channel.socket.nio.NioServerSocketChannel;
    import io.netty.handler.codec.http.HttpRequestDecoder;
    import io.netty.handler.codec.http.HttpResponseEncoder;
    
    public class HttpServer {
    
        public void start(int port) throws Exception {
    
            EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
            EventLoopGroup workerGroup = new NioEventLoopGroup();
            try {
                ServerBootstrap b = new ServerBootstrap(); // (2)
                b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class) // (3)
                        .childHandler(new ChannelInitializer<SocketChannel>() { // (4)
                                    @Override
                                    public void initChannel(SocketChannel ch) throws Exception {
                                        // server端发送的是httpResponse，所以要使用HttpResponseEncoder进行编码
                                        ch.pipeline().addLast(new HttpResponseEncoder());
                                        // server端接收到的是httpRequest，所以要使用HttpRequestDecoder进行解码
                                        ch.pipeline().addLast(new HttpRequestDecoder());
                                        ch.pipeline().addLast(new HttpServerInboundHandler());
                                    }
                                }).option(ChannelOption.SO_BACKLOG, 128) // (5)
                        .childOption(ChannelOption.SO_KEEPALIVE, true); // (6)
    
                ChannelFuture f = b.bind(port).sync(); // (7)
    
                f.channel().closeFuture().sync();
            } finally {
                workerGroup.shutdownGracefully();
                bossGroup.shutdownGracefully();
            }
        }
    
        public static void main(String[] args) throws Exception {
            HttpServer server = new HttpServer();
            server.start(8000);
        }
    }

2.HttpServerInboundHandler解析客户端的请求，并进行响应

package com.bijian.netty.server;
    
    import static io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;
    import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_LENGTH;
    import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
    import static io.netty.handler.codec.http.HttpResponseStatus.OK;
    import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
    import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.ChannelInboundHandlerAdapter;
    import io.netty.handler.codec.http.DefaultFullHttpResponse;
    import io.netty.handler.codec.http.FullHttpResponse;
    import io.netty.handler.codec.http.HttpContent;
    import io.netty.handler.codec.http.HttpHeaders;
    import io.netty.handler.codec.http.HttpHeaders.Values;
    import io.netty.handler.codec.http.HttpRequest;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import com.bijian.netty.util.ByteBufToBytes;
    
    public class HttpServerInboundHandler extends ChannelInboundHandlerAdapter {
        
        private static Logger logger = LoggerFactory.getLogger(HttpServerInboundHandler.class);
        private ByteBufToBytes reader;
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            if (msg instanceof HttpRequest) {
                HttpRequest request = (HttpRequest) msg;
                System.out.println("messageType:" + request.headers().get("messageType"));
                System.out.println("businessType:" + request.headers().get("businessType"));
                if (HttpHeaders.isContentLengthSet(request)) {
                    reader = new ByteBufToBytes((int) HttpHeaders.getContentLength(request));
                }
            }
    
            if (msg instanceof HttpContent) {
                HttpContent httpContent = (HttpContent) msg;
                ByteBuf content = httpContent.content();
                reader.reading(content);
                content.release();
    
                if (reader.isEnd()) {
                    String resultStr = new String(reader.readFull());
                    System.out.println("Client said:" + resultStr);
    
                    FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer("I am ok"
                            .getBytes()));
                    response.headers().set(CONTENT_TYPE, "text/plain");
                    response.headers().set(CONTENT_LENGTH, response.content().readableBytes());
                    response.headers().set(CONNECTION, Values.KEEP_ALIVE);
                    ctx.write(response);
                    ctx.flush();
                }
            }
        }
    
        @Override
        public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
            logger.info("HttpServerInboundHandler.channelReadComplete");
            ctx.flush();
        }
    }

3.HttpClient 向服务器发送请求

package com.bijian.netty.client;
    
    import io.netty.bootstrap.Bootstrap;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.ChannelOption;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.SocketChannel;
    import io.netty.channel.socket.nio.NioSocketChannel;
    import io.netty.handler.codec.http.DefaultFullHttpRequest;
    import io.netty.handler.codec.http.HttpHeaders;
    import io.netty.handler.codec.http.HttpMethod;
    import io.netty.handler.codec.http.HttpRequestEncoder;
    import io.netty.handler.codec.http.HttpResponseDecoder;
    import io.netty.handler.codec.http.HttpVersion;
    
    import java.net.URI;
    
    public class HttpClient {
        
        public void connect(String host, int port) throws Exception {
            
            EventLoopGroup workerGroup = new NioEventLoopGroup();
            
            try {
                Bootstrap b = new Bootstrap(); // (1)
                b.group(workerGroup); // (2)
                b.channel(NioSocketChannel.class); // (3)
                b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
                b.handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    public void initChannel(SocketChannel ch) throws Exception {
                        // 客户端接收到的是httpResponse响应，所以要使用HttpResponseDecoder进行解码
                        ch.pipeline().addLast(new HttpResponseDecoder());
                        // 客户端发送的是httprequest，所以要使用HttpRequestEncoder进行编码
                        ch.pipeline().addLast(new HttpRequestEncoder());
                        ch.pipeline().addLast(new HttpClientInboundHandler());
                    }
                });
    
                // Start the client.
                ChannelFuture f = b.connect(host, port).sync(); // (5)
    
                URI uri = new URI("http://127.0.0.1:8000");
                String msg = "Are you ok?";
                DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST,
                        uri.toASCIIString(), Unpooled.wrappedBuffer(msg.getBytes()));
    
                // 构建http请求
                request.headers().set(HttpHeaders.Names.HOST, host);
                request.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
                request.headers().set(HttpHeaders.Names.CONTENT_LENGTH, request.content().readableBytes());
                request.headers().set("messageType", "normal");
                request.headers().set("businessType", "testServerState");
                // 发送http请求
                f.channel().write(request);
                f.channel().flush();
                f.channel().closeFuture().sync();
            } finally {
                workerGroup.shutdownGracefully();
            }
        }
    
        public static void main(String[] args) throws Exception {
            HttpClient client = new HttpClient();
            client.connect("127.0.0.1", 8000);
        }
    }

4.HttpClientInboundHandler 对服务器的响应进行读取

package com.bijian.netty.client;
    
    import io.netty.buffer.ByteBuf;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.ChannelInboundHandlerAdapter;
    import io.netty.handler.codec.http.HttpContent;
    import io.netty.handler.codec.http.HttpHeaders;
    import io.netty.handler.codec.http.HttpResponse;
    
    import com.bijian.netty.util.ByteBufToBytes;
    
    public class HttpClientInboundHandler extends ChannelInboundHandlerAdapter {
        
        private ByteBufToBytes reader;
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            
            if (msg instanceof HttpResponse) {
                HttpResponse response = (HttpResponse) msg;
                System.out.println("CONTENT_TYPE:" + response.headers().get(HttpHeaders.Names.CONTENT_TYPE));
                if (HttpHeaders.isContentLengthSet(response)) {
                    reader = new ByteBufToBytes((int) HttpHeaders.getContentLength(response));
                }
            }
    
            if (msg instanceof HttpContent) {
                HttpContent httpContent = (HttpContent) msg;
                ByteBuf content = httpContent.content();
                reader.reading(content);
                content.release();
    
                if (reader.isEnd()) {
                    String resultStr = new String(reader.readFull());
                    System.out.println("Server said:" + resultStr);
    
                    ctx.close();
                }
            }
        }
    }

5.ByteBufToBytes 读取NIO的工具类，可以一次性把ByteBuf的数据读取出来，也可以把多次ByteBuf中的数据统一读取出来。

package com.bijian.netty.util;
    
    import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    
    public class ByteBufToBytes {
        
        private ByteBuf temp;
    
        private boolean end = true;
    
        public ByteBufToBytes(int length) {
            temp = Unpooled.buffer(length);
        }
    
        public void reading(ByteBuf datas) {
            datas.readBytes(temp, datas.readableBytes());
            if (this.temp.writableBytes() != 0) {
                end = false;
            } else {
                end = true;
            }
        }
    
        public boolean isEnd() {
            return end;
        }
    
        public byte[] readFull() {
            if (end) {
                byte[] contentByte = new byte[this.temp.readableBytes()];
                this.temp.readBytes(contentByte);
                this.temp.release();
                return contentByte;
            } else {
                return null;
            }
        }
    
        public byte[] read(ByteBuf datas) {
            byte[] bytes = new byte[datas.readableBytes()];
            datas.readBytes(bytes);
            return bytes;
        }
    }

注意事项：

1.可以通过在Netty的Chanel中发送HttpRequest对象，完成发送http请求的要求，同时可以对HttpHeader进行设置。

2.可以通过HttpResponse发送http响应，同时可以对HttpHeader进行设置。

3.上面涉及到的http对象都是Netty自己封装的，不是标准的。

文章来源：[http://blog.csdn.net/u013252773/article/details/21254257][http_blog.csdn.net_u013252773_article_details_21254257]

[2a22e5d9-9a37-3204-86ee-dde07ddcd6ad.jpg]: /images/20220411/a009a8c6d2ee47af8b1f1008cd49501c.png
[http_blog.csdn.net_u013252773_article_details_21254257]: http://blog.csdn.net/u013252773/article/details/21254257