Netty简单的HTTP服务器

本文转载自：https://www.cnblogs.com/luangeng/p/7875710.html

HTTP协议：略

基于Netty的HTTP协议栈可以方便的进行异步非阻塞的HTTP服务器的开发。

当在浏览器中输入一个指向特定网页的URL时，浏览器就会生成一个HTTP请求，浏览器会与服务器建立TCP连接，当TCP可靠连接建立之后，浏览器会将生成的HTTP请求发送到服务器端。这时服务器程序接收到了信息将要去识别这个信息的内容，然后调用相应的服务程序，经过服务程序的分析和处理之后服务器端返回内容给浏览器。当服务器返回了内容给浏览器后，这时浏览器与服务器之间的数据交换完毕，这时TCP可靠连接就会断开。

下面是一个简单的例子，只处理GET请求：

html，css，js，jpg等资源位置如下

HttpServer

package com.luangeng.netty.http;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
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.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
import io.netty.handler.stream.ChunkedWriteHandler;

/**
 * Created by LG on 2017/11/21.
 */
public class HttpServer {

    public void run(final int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch)
                                throws Exception {

                            // HTTP请求消息解码器
                            ch.pipeline().addLast("http-decoder", new HttpRequestDecoder());

                            /*
                             * HttpObjectAggregator解码器
                             * 将多个消息转换为单一的FullHttpRequest或FullHttpResponse对象
                             */
                            ch.pipeline().addLast("http-aggregator", new HttpObjectAggregator(65536));

                            //HTTP响应编码器,对HTTP响应进行编码
                            ch.pipeline().addLast("http-encoder", new HttpResponseEncoder());

                            //ChunkedWriteHandler的主要作用是支持异步发送大的码流,但不占用过多的内存,防止JAVA内存溢出
                            ch.pipeline().addLast("http-chunked",
                                    new ChunkedWriteHandler());

                            ch.pipeline().addLast("httpServerHandler", new HttpServerHandler());
                        }
                    });
            ChannelFuture future = b.bind("localhost", port).sync();
            System.out.println("HTTP Server startup.");
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8080;
        new HttpServer().run(port);
    }

}

---

HttpServerHandler

package com.luangeng.netty.http;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.*;
import io.netty.util.CharsetUtil;

import java.io.File;
import java.io.FileInputStream;
import java.net.URLDecoder;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpMethod.GET;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;

/**
 * Created by LG on 2017/11/21.
 */
public class HttpServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    private static final String BASE_DIR = System.getProperty("user.dir") + "/src/main/java/com/luangeng/netty/http/i";

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {

        //400
        if (!request.decoderResult().isSuccess()) {
            sendError(ctx, HttpResponseStatus.BAD_REQUEST);
            return;
        }

        //405
        if (request.method() != GET) {
            sendError(ctx, HttpResponseStatus.METHOD_NOT_ALLOWED);
            return;
        }

        //404
        String uri = request.uri();
        uri = URLDecoder.decode(uri, "UTF-8");
        uri = uri.replace('/', File.separatorChar);
        File file = new File(BASE_DIR + uri);
        if (!file.exists() || !file.isFile()) {
            sendError(ctx, HttpResponseStatus.NOT_FOUND);
            return;
        }

        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, HttpResponseStatus.OK);

        FileChannel channel = new FileInputStream(file).getChannel();
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        while (channel.read(buffer) != -1) {
            buffer.flip();
            response.content().writeBytes(buffer);
            buffer.clear();
        }
        channel.close();

        if(uri.endsWith(".css")){
            response.headers().set(CONTENT_TYPE, "text/css; charset=UTF-8");
        }else {
            response.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");
        }
        long fileLength = response.content().readableBytes();
        HttpUtil.setContentLength(response, fileLength);

        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        cause.printStackTrace();
        if (ctx.channel().isActive()) {
            sendError(ctx, HttpResponseStatus.INTERNAL_SERVER_ERROR);
        }
    }

    private static void sendError(ChannelHandlerContext ctx,
                                  HttpResponseStatus status) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1,
                status, Unpooled.copiedBuffer("Failure: " + status.toString()
                + "
", CharsetUtil.UTF_8));
        response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");
        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

}

---

hello.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Hello</title>
    <link rel="stylesheet" type="text/css" href="/back.css"/>
    <script src="/jquery-1.11.3.min.js"></script>
</head>
<body>
<div style="background:#98bf21;height:100px;100px;position:absolute;">
</div>

<p>
    一幅图像：
    <img src="/img1.jpg" width="128" height="128"/>
</p>
<p>
    一幅动画图像：
    <img id="img1" src="/eg_cute.gif" width="50" height="50"/>
</p>

<ul>
    <li>咖啡</li>
    <li>茶</li>
    <li>牛奶</li>
</ul>

</body>

<script type="text/javascript">
    $(document).ready(function() {
        timedCount();
    });

    function timedCount() {
        var div=$("div");
        div.animate({height:'300px',opacity:'0.4'},"slow");
        div.animate({'300px',opacity:'0.8'},"slow");
        div.animate({height:'100px',opacity:'0.4'},"slow");
        div.animate({'100px',opacity:'0.8'},"slow");
        t=setTimeout("timedCount()",5000)
    }

</script>
</html>

---

运行结果如下：

可见js，css，jpg等资源都可正常加载，