Use Netty to build a simple HTTP service

Download the netty source code on Github at github.com/netty/netty

See the example

Start by creating an HttpHelloWorldServer as the launch class

/** * An HTTP server that sends back the content of the received HTTP request * in a pretty plaintext form. */ public final class HttpHelloWorldServer { static final boolean SSL = System.getProperty("ssl") ! = null; static final int PORT = Integer.parseInt(System.getProperty("port", SSL? "8443", "8080")); public static void main(String[] args) throws Exception { // Configure SSL. final SslContext sslCtx; if (SSL) { SelfSignedCertificate ssc = new SelfSignedCertificate(); sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build(); } else { sslCtx = null; } // Configure the server. EventLoopGroup bossGroup = new NioEventLoopGroup(1); EventLoopGroup workerGroup = new NioEventLoopGroup(); try { ServerBootstrap b = new ServerBootstrap(); b.option(ChannelOption.SO_BACKLOG, 1024); b.group(bossGroup, workerGroup) .channel(NioServerSocketChannel.class) .handler(new LoggingHandler(LogLevel.INFO)) .childHandler(new HttpHelloWorldServerInitializer(sslCtx)); Channel ch = b.bind(PORT).sync().channel(); System.err.println("Open your web browser and navigate to " + (SSL? "HTTPS" : "HTTP") + ": / / 127.0.0.1:" + PORT + '/'); ch.closeFuture().sync(); } finally { bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); }}}Copy the code

The key code bootstrap class is ServerBootstrap. By assembling the Builder mode of ServerBootstrap, it is easy to create a NetTY

HttpHelloWorldServerInitializer hanler configuration, see HttpHelloWorldServerInitializer code

public class HttpHelloWorldServerInitializer extends ChannelInitializer<SocketChannel> {

    private final SslContext sslCtx;

    public HttpHelloWorldServerInitializer(SslContext sslCtx) {
        this.sslCtx = sslCtx;
    }

    @Override
    public void initChannel(SocketChannel ch) {
        ChannelPipeline p = ch.pipeline();
        if (sslCtx != null) {
            p.addLast(sslCtx.newHandler(ch.alloc()));
        }
        p.addLast(new HttpServerCodec());
        p.addLast(new HttpServerExpectContinueHandler());
        p.addLast(new HttpHelloWorldServerHandler());
    }
}

Copy the code

HttpHelloWorldServerHandler handler class for us

public class HttpHelloWorldServerHandler extends SimpleChannelInboundHandler<HttpObject> { private static final byte[] CONTENT = { 'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd' }; @Override public void channelReadComplete(ChannelHandlerContext ctx) { ctx.flush(); } @Override public void channelRead0(ChannelHandlerContext ctx, HttpObject msg) { if (msg instanceof HttpRequest) { HttpRequest req = (HttpRequest) msg; boolean keepAlive = HttpUtil.isKeepAlive(req); FullHttpResponse response = new DefaultFullHttpResponse(req.protocolVersion(), OK, Unpooled.wrappedBuffer(CONTENT)); response.headers() .set(CONTENT_TYPE, TEXT_PLAIN) .setInt(CONTENT_LENGTH, response.content().readableBytes()); if (keepAlive) { if (! req.protocolVersion().isKeepAliveDefault()) { response.headers().set(CONNECTION, KEEP_ALIVE); } } else { // Tell the client we're going to close the connection. response.headers().set(CONNECTION, CLOSE); } ChannelFuture f = ctx.write(response); if (! keepAlive) { f.addListener(ChannelFutureListener.CLOSE); } } } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { cause.printStackTrace(); ctx.close(); }}Copy the code

1. ChannelRead0 processing method for receipt of a request, through the HttpHelloWorldServerInitializer HttpServerCodec, HttpServerExpectContinueHandler, Netty has helped us to handle the HTTP codec, as long as the HttpHelloWorldServerHandler plus our business processing logic