暴露服务

• 服务之间的通信协议采用http协议，所以在服务provider中启动tomcat暴露服务
• 添加内嵌tomcat的依赖

<dependencies>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-core</artifactId>
        <version>9.0.12</version>
    </dependency>
</dependencies>

• 创建HttpServer

public class HttpServer {

    /**
     * tomca t服务启动
     * 参考tomcat配置
     * <Server port= "8005" shutdown="SHUTDOWN">
     * <Service name="Catalina">
     * <Connector port="8080" protocol="HTTP/1.1"
     * connectionTimeout="20000"
     * redirectPort="8443"
     * URIEncoding="UTF-8"/>
     * <Engine name="Catalina" defaultHost="localhost"/>
     * <Host name="localhost" appBase="webapps"
     * unpackWARs= "true" autoDeploy="true">
     * <Context path="" doBase= "WORKDIR" reloadable="true"/>
     * </Host>
     * </Engine>
     * </Service>
     * </Server>
     */

    public void start(String hostname,int port){
        //实例一个tomcat
        Tomcat tomcat=new Tomcat();

        //构建一个server
        Server server=tomcat.getServer();

        //构建service
        Service service = tomcat.getService();

        //获取service
        Connector connector = new Connector();
        connector.setPort(port);
        connector.setURIEncoding("UTF-8");

        //构建Engine
        Engine engine = new StandardEngine();

        //构建host
        Host host = new StandardHost();

        //构建Context
        String contextPath="";
        Context context = new StandardContext();
        context.setPath(contextPath);
        context.addLifecycleListener(new Tomcat.FixContextListener());//生命周期监听器

        //然后按照server.xml，一层层把子节点添加到父节点
        host.addChild(context);
        engine.addChild(context);
        service.setContainer(engine);
        service.addConnector(connector);
        //service在getServer时就被添加到Server节点了

        //tomcat是一个servlet，设置路径与映射
        tomcat.addServlet(contextPath,"dispatcher",new DispatcherServlet());
        context.addServletMappingDecoded("/*","dispatcher");

        try{
            tomcat.start();//启动tomcat
            tomcat.getServer().await();//接受请求

        } catch (LifecycleException e) {
            e.printStackTrace();
        }
    }
}

• DispatcherServlet

public class DispatcherServlet extends HttpServlet {
    @Override
    public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //HttpServerHandler是真正处理远程调用请求的
        new HttpServerHandler().handler(req,resp);
    }
}

• HttpServerHandler处理远程调用请求

public class HttpServerHandler {

    public void handler(HttpServletRequest req, HttpServletResponse resp){
        try{
            //服务器的处理逻辑

            //1.通过请求流获取请求服务调用的参数
            InputStream inputStream=req.getInputStream();
            ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
            Invocation invocation = (Invocation) objectInputStream.readObject();

            //2.从注册中心获取服务列表
            Class implClass = NativeRegistry.get(new URL("localhost",8080),invocation.getInterfaceName());

            //3.调用服务 反射
            Method method = implClass.getMethod(invocation.getMethodName(), invocation.getParamTypes());
            String result = (String) method.invoke(implClass.newInstance(), invocation.getParams());

            //4.结果返回
            IOUtils.write(result,resp.getOutputStream());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}