Okra通过封装成熟高效的框架以简化应用程序服务器构建的过程。上一篇介绍了使用Okra快速搭建Socket服务器。 本篇承接上一篇，介绍快速搭建简单高性能的Http服务器。

这里需要说明一下Okra框架不适用于web服务器。Okra的通信是基于Netty框架的，而Netty本身不提供强有力的web相关功能支持。 但是作为app或者是网页游戏的短连接服务器，Okra还是绰绰有余的。

1. 创建Executor

和Socket服务器搭建流程类似。首先实现一个简单的HttpRequestExecutor，用于处理Http请求:

public class HttpRequestExecutor implements Executor {private static final Logger LOG = LogManager.getLogger(HttpRequestExecutor.class);protected Session session;protected FullHttpRequest request;public HttpRequestExecutor(Session session, FullHttpRequest request) {this.session = session;this.request = request;}@Overridepublic void onExecute() {if (null == request) {throw new NullPointerException("request");}try {QueryStringDecoder decoder = new QueryStringDecoder(request.getUri());switch (decoder.path()) {case "/test":response(session.ctx(), "{state:0}");return;case "/favicon.ico":break;}simple(session.ctx().channel(), HttpResponseStatus.FORBIDDEN);} catch (Exception e) {session.ctx().close();LOG.info("HTTP Api throw exception : ", e);}}private static void simple(Channel channel, HttpResponseStatus status) {ChannelFuture channelFuture = channel.writeAndFlush(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, status));channelFuture.addListener(ChannelFutureListener.CLOSE);}private static void response(ChannelHandlerContext ctx, String msg) {HttpResponse response;if (msg != null) {ByteBuf byteBuf = Unpooled.wrappedBuffer(msg.getBytes());response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, byteBuf);} else {response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);}ChannelFuture channelFuture = ctx.channel().writeAndFlush(response);channelFuture.addListener(ChannelFutureListener.CLOSE);}@Overridepublic void release() {this.session = null;this.request = null;}
}

Okra提供了封装好的Disruptor桥用于Netty结合Disruptor。Okra通过Executor工厂让用户可以便捷灵活的定制特殊的处理者. 继承DisruptorAdapterBy41xHandler（依赖于Netty4.1.x）或者DisruptorAdapterHandler（依赖于Netty4.0.x）实现创建HttpRequestExecutor的Executor工厂。

public class ExampleApiHandler extends DisruptorAdapterBy41xHandler<FullHttpRequest> {@Overrideprotected Executor newExecutor(Session session, FullHttpRequest msg) {return new HttpRequestExecutor(session, msg);}
}

2. 创建Server

然后创建一个Server继承TcpProtocolServer实现自己的服务器类. 增加Handler处理

public class HttpServer extends TcpProtocolServer {public HttpServer(int port) {setPort(port);}@Overrideprotected ChannelHandler newChannelInitializer() {return new ChannelInitializer<NioSocketChannel>() {@Overrideprotected void initChannel(NioSocketChannel ch) throws Exception {ChannelPipeline cp = ch.pipeline();cp.addLast("decoder", new HttpRequestDecoder());cp.addLast("encoder", new HttpResponseEncoder());cp.addLast("aggregator", new HttpObjectAggregator(1048576));cp.addLast("handler", new ExampleApiHandler());}};}
}

3. 启动服务器

假如你的项目中使用了Spring框架，那么只需要在配置如下bean就可以启动:

<!-- Http protocol server -->
<bean id="httpServer" class="org.ogcs.okra.example.http.HttpServer" init-method="start" destroy-method="stop"><constructor-arg name="port" value="${http.port}"/>
</bean>

普通Java程序:

HttpServer server = new HttpServer(9005);
server.start();

只需要简短的两行代码就可以启动服务器了。

4. 总结

和搭建Socket服务器基本类似。更换了处理协议的Handler和处理并发任务的Executor。基本结构并无太大变更（感谢Netty框架，呦吼！） 本文介绍了使用Okra快速搭建高可用，高性能，可扩展，高并发服务器的示例。Okra通过封装，简化了服务器搭建过程。