前言：对于微服务来说，如果咱们要实现一个web服务，
大部分人可能间接用springboot的spring-boot-starter-web了。
咱们晓得spring-boot-starter-web默认实现是tomcat，当然你也能够抉择其余服务器类型，比方Jetty、Undertow等。
然而如果是一个非springboot我的项目，该如何实现呢？
这里介绍了下四种实现形式，基于Tomcat、Jetty、JdkHttp、Netty实现内嵌web容器。
Tomcat
依赖的maven坐标：
<dependency> <groupId>javax.annotation</groupId> <artifactId>javax.annotation-api</artifactId> </dependency> <dependency> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-core</artifactId> <exclusions> <!--避免注解抵触，排除tomcat自带注解，springboot也是这样设置的--> <exclusion> <artifactId>tomcat-annotations-api</artifactId> <groupId>org.apache.tomcat</groupId> </exclusion> </exclusions> </dependency>首先看下初始化启动的代码：
Tomcat tomcatServer = new Tomcat();//静默形式启动tomcatServer.setSilent(true);tomcatServer.setPort(8080);//是否设置主动部署tomcatServer.getHost().setAutoDeploy(false);//创立上下文,拿到上下文后就能够设置整个拜访地址了StandardContext standardContext = new StandardContext();standardContext.setPath(CONTEX_PATH);//监听上下文standardContext.addLifecycleListener(new Tomcat.FixContextListener());// tomcat容器增加standardContext 增加整个contexttomcatServer.getHost().addChild(standardContext);// 创立servlet servlet的名字叫IndexServlettomcatServer.addServlet(CONTEX_PATH, SERVLET_NAME, new JdkSimpleDispatchServlet());// 增加servleturl映射standardContext.addServletMappingDecoded("/*", SERVLET_NAME);try { tomcatServer.start(); server = tomcatServer;} catch (Exception e) {}下面tomcat在注册servlet的时候，自定义了一个Servlet，而后映射了/*的申请。能够查看下JdkSimpleDispatchServlet这个类，代码如下：
@Slf4jpublic class JdkSimpleDispatchServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { log.info("path:{}, clientIp:{}", req.getRequestURL(), req.getRemoteHost()); PrintWriter writer = resp.getWriter(); writer.print("this is index"); writer.close(); }}Jetty
Jetty和tomcat十分相似，也是调用start办法启动。
maven依赖如下：
<dependency> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-server</artifactId> </dependency> <!--增加servlet模块--> <dependency> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-servlet</artifactId> </dependency>jetty服务初始化代码更简略，如下:
Server server = new Server(NetworkUtil.getHealthServerPort());// ServletHandler是一种简略的创立上下文处理程序的简略办法，该上下文处理程序由Servlet实例反对。而后，须要将该处理程序注册到Server对象。ServletHandler handler = new ServletHandler();server.setHandler(handler);// 这是原始Servlet，而不是已配置的Servlet，JdkSimpleDispatchServlet和tomcat的相似handler.addServletWithMapping(JdkSimpleDispatchServlet.class, "/*");try { // Start things up! server.start(); jetty = server;} catch (Exception e) {}Netty
说了Tomcat和Jetty，咱们再看下Netty，之前所在的一家公司就是基于Netty封装了Web服务，Netty对Web反对也比较完善，默认基于NIO的多路复用IO模型反对单机上万的吞肚量。
看下pom依赖：
<dependency> <groupId>io.netty</groupId> <artifactId>netty-all</artifactId> </dependency>启动形式：
public class NettyHttpServerHealthCheckServer implements IHealthCheckServer { private static ExecutorService Pool = Executors.newSingleThreadExecutor( new NamedThreadFactory("Netty-HealthCheck-Pool", true)); ServerBootstrap bootstrap = new ServerBootstrap(); // boss线程，只需一个 EventLoopGroup boss = new NioEventLoopGroup(); // work线程 EventLoopGroup work = new NioEventLoopGroup(); @Override public void start() { try { // 因为监听服务是阻塞的，须要线程池异步监听 Pool.execute(() -> { try { // 配置channel、handle bootstrap.group(boss, work)// .handler(new LoggingHandler(LogLevel.INFO)) .channel(NioServerSocketChannel.class) // HttpServerInitializer即http编码解码和解决配置器 .childHandler(new HttpServerInitializer()); ChannelFuture f = bootstrap.bind(new InetSocketAddress(NetworkUtil.getHealthServerPort())).sync(); // 阻塞监听 f.channel().closeFuture().sync(); } catch (Exception e) { } }); } catch (Exception e) { return; } } @Override public void stop() { boss.shutdownGracefully(); work.shutdownGracefully(); } class HttpServerInitializer extends ChannelInitializer<SocketChannel> { @Override protected void initChannel(SocketChannel channel) throws Exception { ChannelPipeline pipeline = channel.pipeline(); pipeline.addLast(new HttpServerCodec());// http 编解码 pipeline.addLast("httpAggregator", new HttpObjectAggregator(512 * 1024)); // http 音讯聚合器 512*1024为接管的最大contentlength pipeline.addLast(new HttpRequestHandler());// 申请处理器 } } class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> { @Override public void channelReadComplete(ChannelHandlerContext ctx) { ctx.flush(); } @Override protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest req) throws Exception { /** * 100 Continue * 是这样的一种状况：HTTP客户端程序有一个实体的主体局部要发送给服务器，但心愿在发送之前查看下服务器是否会 * 承受这个实体，所以在发送实体之前先发送了一个携带100 * Continue的Expect申请首部的申请。服务器在收到这样的申请后，应该用 100 Continue或一条错误码来进行响应。 */ if (is100ContinueExpected(req)) { ctx.write(new DefaultFullHttpResponse( HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE)); } // 获取申请的uri String path = req.uri(); // 响应申请 fireResponse(ctx, HttpResponseStatus.OK, "hello", "text/html; charset=utf-8"); } private void fireResponse(ChannelHandlerContext ctx, HttpResponseStatus httpResponseStatus, String resp, String contentType) { FullHttpResponse responseDown = new DefaultFullHttpResponse( HttpVersion.HTTP_1_1, httpResponseStatus, Unpooled.copiedBuffer(resp, Charset.defaultCharset())); responseDown.headers().set(HttpHeaderNames.CONTENT_TYPE, contentType); ctx.writeAndFlush(responseDown).addListener(ChannelFutureListener.CLOSE); } }}从下面代码能够得悉，Netty默认就提供了http编解码和协定的实现，十分不便。
JdkHttp
最好介绍下不依赖第三方实现，应用JDK8内置的Http Server实现。
HttpServer类
外围类HttpServer，HttpServer是属于rt包的类，须要下载rt包的源码，配置到IDEA。或者间接应用openjdk，也能够查看到源码。
rt包能够下载OpenJDK的源码，https://download.java.net/openjdk/jdk8/promoted/b132/openjdk-8-src-b132-03_mar_2014.zip
HttpServer源码：
package com.sun.net.httpserver;@Exportedpublic abstract class HttpServer { protected HttpServer() { } public static HttpServer create() throws IOException { return create((InetSocketAddress)null, 0); } public static HttpServer create(InetSocketAddress var0, int var1) throws IOException { HttpServerProvider var2 = HttpServerProvider.provider(); return var2.createHttpServer(var0, var1); } public abstract void bind(InetSocketAddress var1, int var2) throws IOException; public abstract void start(); public abstract void setExecutor(Executor var1); public abstract Executor getExecutor(); public abstract void stop(int var1); public abstract HttpContext createContext(String var1, HttpHandler var2); public abstract HttpContext createContext(String var1); public abstract void removeContext(String var1) throws IllegalArgumentException; public abstract void removeContext(HttpContext var1); public abstract InetSocketAddress getAddress();}初始化Http服务：
public class JDKHttpServerHealthCheckServer implements IHealthCheckServer { HttpServer server; @Override public void start() { try { // 初始化监听 server = HttpServer.create(new InetSocketAddress(8080), 100); // 注册http申请解决类 server.createContext("/", new JdkHttpHandler()); // 启动服务 server.start(); } catch (Exception e) { return; } } @Override public void stop() { if (server != null) { server.stop(0); } } static class JdkHttpHandler implements HttpHandler { @Override public void handle(HttpExchange httpExchange) throws IOException { String path = httpExchange.getRequestURI() == null ? "/" : httpExchange.getRequestURI().getPath(); try { CharArrayWriter charArrayWriter = new CharArrayWriter(); charArrayWriter.write("hello"); httpExchange.getResponseHeaders().add("Content-Type", "text/plain; charset=utf-8"); // 这里必须指定字节大小，因为默认是固定大小的编码解码实现 httpExchange.sendResponseHeaders(200, charArrayWriter.size()); outputStream.write(charArrayWriter.toString().getBytes()); } catch (Exception e) { httpExchange.sendResponseHeaders(500, 0); } } }}从下面四个实现来看，对http servlet标准反对比较完善的有Jetty、Tomcat。性能高的是Netty，实现最简略的是JDK默认HttpServer。
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