之前在前一篇的《Netty自娱自乐之协议栈设计》，菜鸟我已经自娱自乐了设计协议栈，gitHub地址为https://github.com/vOoT/ncustomer-protocal。先这一篇中，准备接着自娱去实现一个RPC框架，现在公司共的是Dubbo,那么先不看其代码，先自行实现一下吧。
dubbo 包括 注册和服务调用，细节我们先不管，然后，我先先实现一个如下的简单模型
哈哈哈，第一个版本就是这么简单，粗暴。说到自定义配置，首先想到的是Spring 自定义标签，利用标签进行配置服务。而我设计的标签页非常的简单，使用如下：
<rpc:provider />
<rpc:cumsumer interface="com.qee.rpc.HelloService"/>
看到了没，非常像dubbo,那么如何实现一个自定义标签呢，从网上可以了解搜索的到，现在我就简单说明一下，如何编写和测试自己自定义的Spring 标签。
一、 定义xsd 文件，该文件是xml文件的 schema 定义。从上面的例子中，我们知道xsd文件里面应该有2个节点，1个provider节点和1个cumsumer节点定义。然后制定provider节点有id 和classs属性，而cumsumer节点有 id和 interface属性。定义文件如下（该文件名为light-weight-rpc.xsd）：
<?xml version="1.0" encoding="UTF-8"?><xsd:schema xmlns="http://www.qee.com/schema/rpc" ???????????xmlns:xsd="http://www.w3.org/2001/XMLSchema" ???????????xmlns:beans="http://www.springframework.org/schema/beans" ???????????targetNamespace="http://www.qee.com/schema/rpc" ???????????elementFormDefault="qualified" ???????????attributeFormDefault="unqualified"> ???<xsd:import namespace="http://www.springframework.org/schema/beans"/> ???<xsd:element name="provider" type="rpc-provider-type"></xsd:element> ???<xsd:element name="cumsumer" type="rpc-cumsumer-type"></xsd:element> ???<xsd:complexType name="rpc-provider-type"> ???????<xsd:attribute name="id" type="xsd:string" use="required"></xsd:attribute> ???????<xsd:attribute name="class" type="xsd:string" use="required"></xsd:attribute> ???</xsd:complexType> ???<xsd:complexType name="rpc-cumsumer-type"> ???????<xsd:attribute name="id" type="xsd:string" use="required"></xsd:attribute> ???????<xsd:attribute name="interface" type="xsd:string" use="required"></xsd:attribute> ???</xsd:complexType></xsd:schema>
上面，画上红线的地方需要注意和主要的关注点，首先需要说明这个文件的name space 为xmlns="http://www.qee.com/schema/rpc 。其他的具体如何写可以到网上搜索。有了这个文件，我们需要在xml的文件引入他，比如如下test.xml文件如何引用该文件
<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans" ??????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
??????xmlns:rpc="http://www.qee.com/schema/rpc" ??????xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd ???????http://www.qee.com/schema/rpc http://www.qee.com/schema/rpc/light-weight-rpc.xsd"> ???<rpc:provider /> ???<rpc:cumsumer interface="com.qee.rpc.HelloService"/></beans>
上面就是一个spring xml 文件，主要关注的是花黄线的部分，这样就可以使用<rpc:provider> 和<rpc:cumsumer>。
二、组织文件，即要把文件放到合适的地方，让Spring能够识别。第一步，需要把light-weight-rpc.xsd文件放到META-INF的文件夹下，然后在META-INF文件创建2个新的文件，名字固定。
文件1:spring.schemes ,该文件里面直有一行数据，如下
??????http\://www.qee.com/schema/rpc/light-weight-rpc.xsd=META-INF/light-weight-rpc.xsd
该行告诉Spring容器,http://www.qee.com/schema/rpc/light-weight-rpc.xsd ,之前定义命名空间的light-weight-rpc.xsd文件是META-INF下的light-weight-rpc.xsd
文件2:spring.handlers,该文件里面也只有一行数据，如下
??????http\://www.qee.com/schema/rpc=com.qee.rpc.config.support.LightWeightRpcNamespaceHandlerSupport
该行告诉Spring容器，命名空间http://www.qee.com/schema/rpc的解析处理器是com.qee.rpc.config.support.LightWeightRpcNamespaceHandlerSupport。这个例子的目录如下
好了到现在我们基本把文件的位置放置正确了。之后就是需要编写com.qee.rpc.config.support.LightWeightRpcNamespaceHandlerSupport。
三、编写com.qee.rpc.config.support.LightWeightRpcNamespaceHandlerSupport，该类需要继承NamespaceHandlerSupport，重写init()方法。主要的目的就是注册，节点解析处理器。
代码如下：
public class LightWeightRpcNamespaceHandlerSupport extends NamespaceHandlerSupport { ???@Override ???public void init() { ???????//注册用于解析<rpc>的解析器 ???????registerBeanDefinitionParser("provider", new LightWeightRpcBeanDefinitionParser()); ???????registerBeanDefinitionParser("cumsumer", new LightWeightRpcBeanDefinitionParser()); ???}}从代码上我们只要，就是把解析xml文件provider和cumsumer节点进行BeanDefinition转化解析。
因为这2个节点非常的类型。所以我就只想用痛一个解析处理器，LightWeightRpcBeanDefinitionParser，该转化器继承org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser。具体代码如下：
public class LightWeightRpcBeanDefinitionParser extends AbstractSingleBeanDefinitionParser { ???protected Class getBeanClass(Element element) { ???????return LightWeightRPCElement.class; ???} ???protected void doParse(Element element, BeanDefinitionBuilder bean) { ???????String interfaces = element.getAttribute("interface"); ???????String clazz = element.getAttribute("class"); ???????String id = element.getAttribute("id"); ???????bean.addPropertyValue("id", id + "Config"); ???????if (StringUtils.hasText(id)) { ???????????bean.addPropertyValue("beanName", id); ???????} ???????if (StringUtils.hasText(clazz)) { ???????????bean.addPropertyValue("clazz", clazz); ???????} ???????if (StringUtils.hasText(interfaces)) { ???????????bean.addPropertyValue("interfaces", interfaces); ???????} ???}}我们把xml的id 放到bean 的beanName，把id+"Config"放到 id上，因为这个BeanDefinitionBuilder 最终生成的对象是LightWeightRPCElement，不是我们需要的代码对象。
@Data@ToStringpublic class LightWeightRPCElement {private String id;
private String beanName;
private String clazz;
private String interfaces;
}
是不是非常的简单，到目前为止，我们已经完成了所有的自定义标签工作，下一步当然就是测试一下啦，代码如下：
public class RPCTest { ???public static void main(String[] args) { ???????ApplicationContext ctx = new ClassPathXmlApplicationContext("test.xml"); ???????LightWeightRPCElement p1= (LightWeightRPCElement)ctx.getBean("helloServiceImplConfig"); ???????LightWeightRPCElement p2= (LightWeightRPCElement)ctx.getBean("helloServiceConfig"); ???????System.out.println(p1); ???????System.out.println(p2); ???}}执行结果是：
四、这一步的话，我们需要处理之前已经注册到Spring的LightWeightRPCElement 的对象，在上面的例子中，这两个的Bean Id分别是helloServiceImplConfig、helloServiceConfig，之后我们需要通过这2个对象来产生我们需要代理对象。首先我们来看一下JDK的生成代理对象的方法：
public static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces,InvocationHandler invocationHandler)；
从上面的代码中，我们知道生产一个代理对象需要一个类加载器loader,和代理接口的字节码interfaces,和代理处理具柄invocationHandler。那么我程序定义了一个名为InterfaceProxyHandler的代理处理具柄，它继承InvocationHandler。代码如下：
@Datapublic class InterfaceProxyHandler implements InvocationHandler { ???private CallBackExcuteHandler excuteHandler; ???public InterfaceProxyHandler(CallBackExcuteHandler excuteHandler) { ???????this.excuteHandler = excuteHandler; ???} ???@Override ???public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { ???????MessageCallback callback = ExcuteManager.invoke(excuteHandler); ???????.......//这里代码还没写，其实就是处理返回结果，准备下章解决。 ???}}从上面的代码，我们知道，它具体的执行逻辑是invoke方法。具体内容就是通过一个ExcuteManager来处理逻辑，该ExcuteManager就是一个封装了ExecutorService的线程池管理类。其意思是每个代理对象去执行方法时，都是通过线程池的一个线程去执行，而这个线程池管理类的执行方法invoke需要一个Callable任务,所以程序自定义了一个CallBackExcuteHandler类。代码如下：
public class CallBackExcuteHandler implements Callable<MessageCallback> { ???private String beanName; ???private List<InetSocketAddress> remoteAddresses; ???private LoadBalancedStrategy loadBalancedStrategy; ???public CallBackExcuteHandler(String beanName) { ???????this.beanName = beanName; ???} ???public CallBackExcuteHandler(String beanName, List<InetSocketAddress> remoteAddresses) { ???????this.beanName = beanName; ???????this.remoteAddresses = remoteAddresses; ???} ???public CallBackExcuteHandler(String beanName, List<InetSocketAddress> remoteAddresses, LoadBalancedStrategy loadBalancedStrategy) { ???????this.beanName = beanName; ???????this.remoteAddresses = remoteAddresses; ???????this.loadBalancedStrategy = loadBalancedStrategy; ???} ???public CallBackExcuteHandler() { ???} ???/** ????* 线程执行 ????* ????* @return ????* @throws Exception ????*/ ???@Override ???public MessageCallback call() throws Exception { ???????if (CollectionUtils.isEmpty(remoteAddresses)) { ???????????List<ServiceAddressConfig> remoteUrls = ServiceRemoteUrlContext.getInstance().getRemoteUrls(beanName); ???????????if (CollectionUtils.isEmpty(remoteUrls)) { ???????????????throw new RuntimeException("服务 [" + beanName + " ]远程地址错误"); ???????????} ???????} ???????int size = remoteAddresses.size(); ???????int idx = loadBalancedStrategy.strategy(size); ???????InetSocketAddress inetSocketAddress = remoteAddresses.get(idx); ???????System.out.println("返回的地址" + inetSocketAddress + " ?idx=" + idx); ???????MessageCallback messageCallback = new MessageCallback(); ???????return messageCallback; ???}}具体逻辑就是看call,这里就是处理的具体逻辑，这个逻辑其实就是处理Netty网络通信的内容，等下章开始讲解，这一章主要通过搭建具体的框架，之后补充细节。这里远程地址为空的话，去远程地址管理上下文获取，接着通过一个负载均衡策略对象，返回其中一个地址的index。通过这种方式实现负载均衡调用。
远程地址管理上下文对象代码如下：
public class ServiceRemoteUrlContext { ???private Map<String, List<ServiceAddressConfig>> remoteUrls; ???private volatile static ServiceRemoteUrlContext context; ???private ServiceRemoteUrlContext() { ???} ???public static ServiceRemoteUrlContext getInstance() { ???????if (context == null) { ???????????synchronized (ServiceRemoteUrlContext.class) { ???????????????if (context == null) { ???????????????????context = new ServiceRemoteUrlContext(); ???????????????????context.remoteUrls = new HashMap<>(); ???????????????} ???????????} ???????} ???????return context; ???} ???/** ????* 添加一个远程地址，地址从service-url.properties 获取 ????* ????* @param beanName ????* @param serviceAddressConfig ????* @return ????*/ ???public boolean addServiceAddress(String beanName, ServiceAddressConfig serviceAddressConfig) { ???????if (StringUtils.isEmpty(beanName) || serviceAddressConfig == null) { ???????????return false; ???????} ???????synchronized (remoteUrls) { ???????????if (remoteUrls.get(beanName) == null) { ???????????????List<ServiceAddressConfig> remoteAddress = new ArrayList<>(); ???????????????remoteAddress.add(serviceAddressConfig); ???????????????remoteUrls.put(beanName, remoteAddress); ???????????} else { ???????????????List<ServiceAddressConfig> serviceAddressConfigs = remoteUrls.get(beanName); ???????????????if (serviceAddressConfigs.contains(serviceAddressConfig)) { ???????????????????return false; ???????????????} ???????????????serviceAddressConfigs.add(serviceAddressConfig); ???????????????return true; ???????????} ???????} ???????return false; ???} ???/** ????* 获取一个服务的远程地址 ，beanName like "com.qee.rpc.config.test.HelloService" ????* ????* @param beanName ????* @return ????*/ ???public List<ServiceAddressConfig> getRemoteUrls(String beanName) { ???????return remoteUrls.get(beanName); ???}}负载均衡的接口，代码如下：
public interface LoadBalancedStrategy { ???/** ????* 从 0 -size-1 获取一个值 ????* ????* @param size ????* @return ????*/ ???int strategy(int size);}现在只实现了1中，轮询方法，之后可以写成可配置，代码如下：
public class RollPolingStrategy implements LoadBalancedStrategy { ???private int currentValue = 0; ???private Class<?> clazz; ???public RollPolingStrategy(Class<?> clazz) { ???????this.clazz = clazz; ???} ???@Override ???public int strategy(int size) { ???????synchronized (clazz) { ???????????int nextValue = (currentValue + 1) % size; ???????????currentValue = nextValue; ???????????if (currentValue > size) { ???????????????nextValue = 0; ???????????} ???????????return currentValue; ???????} ???}}接着，我们需要看一下简单的ExcuteManager类，代码如下：
public class ExcuteManager { ???/** ????* 默认是200个线程 ????*/ ???private static final int DEFAULT_THRED_NUM = 200; ???/** ????* 超时时间为1秒 ????*/ ???private static final int DEFAULT_TIME_OUT_TIME = 1000; ???private static ExecutorService executorService = Executors.newFixedThreadPool(DEFAULT_THRED_NUM); ???public static MessageCallback invoke(Callable<MessageCallback> call) { ???????Future<MessageCallback> submit = executorService.submit(call); ???????try { ???????????return submit.get(DEFAULT_TIME_OUT_TIME, TimeUnit.MILLISECONDS); ???????} catch (InterruptedException e) { ???????????submit.cancel(true); ???????????throw new RuntimeException("the method is interupted ", e); ???????} catch (ExecutionException e) { ???????????submit.cancel(true); ???????????throw new RuntimeException("the method cal excute exception", e); ???????} catch (TimeoutException e) { ???????????System.out.println(Thread.currentThread().getName()); ???????????submit.cancel(true); ???????????throw new RuntimeException("the method call is time out ?", e); ???????} ???} ???public static void shutdown() { ???????executorService.shutdown(); ???} ???public static void shutdownNow() { ???????executorService.shutdownNow(); ???}}这些参数，在后面都做成可配置的。
最后一步了，就是需要生产一个代理对象，并把代理对象注册到Spring容器里面。那么Spring的BeanPostProcessor可以为我们解决问题，看代码如下：
@Componentpublic class RegisterRpcProxyBeanProcessor implements BeanPostProcessor, BeanFactoryAware { ???private BeanFactory beanFactory; ???@Override ???public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { ???????return bean; ???} ???@Override ???public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { ???????Object target = bean; ???????if (bean instanceof LightWeightRPCElement) { ???????／／如果是LightWeightRPCElement，则强转，否则不处理 ???????????LightWeightRPCElement rpcElement = (LightWeightRPCElement) bean; ??????????????????????／／ 接着就是获取 之前XML 的属性值 ???????????Class<?> clazz = null; ???????????if (!StringUtils.isEmpty(rpcElement.getInterfaces())) { ???????????????try { ???????????????????clazz = Class.forName(rpcElement.getInterfaces()); ???????????????} catch (ClassNotFoundException e) { ???????????????????throw new RuntimeException("获取 [" + rpcElement.getInterfaces() + " ] class字节码失败"); ???????????????} ???????????} ????????????／／通过ServiceRemoteUrlContext得到这个接口的远程端口和地址 ???????????List<ServiceAddressConfig> remoteUrls = ServiceRemoteUrlContext.getInstance().getRemoteUrls(rpcElement.getInterfaces()); ???????????List<InetSocketAddress> remoteAddressList = ExtractUtil.extractList(remoteUrls, "remoteAddress", ServiceAddressConfig.class); ???????????CallBackExcuteHandler callBackExcuteHandler = new CallBackExcuteHandler(rpcElement.getInterfaces(), remoteAddressList,new RollPolingStrategy(clazz)); ???????????InterfaceProxyHandler interfaceProxyHandler = new InterfaceProxyHandler(callBackExcuteHandler); ???????????／／这里之后可以优化为各种方式产生动态代理，如cglib等 ???????????target = Proxy.newProxyInstance(bean.getClass().getClassLoader(), new Class[]{clazz}, interfaceProxyHandler); ???????????if (beanFactory instanceof DefaultListableBeanFactory) { ???????????????／／这里就是动态注册对象，把动态代理对象注册到Spring上 ???????????????DefaultListableBeanFactory defaultFactory = (DefaultListableBeanFactory) beanFactory; ???????????????defaultFactory.registerSingleton(rpcElement.getBeanName(), target); ???????????} ???????} ???????return target; ???} ???@Override ???public void setBeanFactory(BeanFactory beanFactory) throws BeansException { ???????this.beanFactory = beanFactory; ???} ????从上面的注释大家应该也非常的清楚了，现在只剩下最后一步了，如何获取该接口的远程服务地址和端口，dubbo是通过注册中心zookeeper,而这里的简单的采用配置，例子如下：
??com.qee.rpc.config.test.HelloService 127.0.0.1:8888,127.0.0.1:7777,127.0.0.1:9999
对，就是在一个properties文件上 通过服务接口全称 和指定远程服务主机和端口。之后可以改为有注册中心的方式。现在我们来看一下读取这个配置的类，代码如下：
@Componentpublic class ServiceRemoteUrlsInit implements InitializingBean { ???/** ????* 远程服务配置地址路径，默认 ????*/ ???@Value("${remote-urls-path:classpath:service-urls.properties}") ???private String remoteUrlsPropertyPath; ???@Override ???public void afterPropertiesSet() throws Exception { ???????Properties pps = new Properties(); ???????if (!remoteUrlsPropertyPath.startsWith("classpath")) { ???????????throw new RuntimeException(remoteUrlsPropertyPath + "不存在"); ???????} ???????String[] filePath = remoteUrlsPropertyPath.split(":"); ???????if (filePath == null || filePath.length != 2) { ???????????throw new RuntimeException(remoteUrlsPropertyPath + "内容配置错误"); ???????} ???????ClassPathResource resource = new ClassPathResource(filePath[1]); ???????InputStream in = new BufferedInputStream(resource.getInputStream()); ???????pps.load(in); ???????Enumeration en = pps.propertyNames(); ???????while (en.hasMoreElements()) { ???????????String beanName = (String) en.nextElement(); ???????????String strRemoteUrls = pps.getProperty(beanName); ???????????String[] remoteUrls = strRemoteUrls.split(","); ???????????if (remoteUrls == null || remoteUrls.length == 0) { ???????????????break; ???????????} ???????????for (String remoteUrl : remoteUrls) { ???????????????String[] hostPort = remoteUrl.split(":"); ???????????????if (hostPort == null || hostPort.length != 2) { ???????????????????throw new RuntimeException(remoteUrlsPropertyPath + " 配置内容错误"); ???????????????} ???????????????ServiceAddressConfig serviceAddressConfig = new ServiceAddressConfig(); ???????????????serviceAddressConfig.setBeanName(beanName); ???????????????serviceAddressConfig.setHostName(hostPort[0]); ???????????????serviceAddressConfig.setRemotePort(Integer.valueOf(hostPort[1])); ???????????????InetSocketAddress socketAddress = new InetSocketAddress(serviceAddressConfig.getHostName(), serviceAddressConfig.getRemotePort()); ???????????????serviceAddressConfig.setRemoteAddress(socketAddress); ???????????????ServiceRemoteUrlContext.getInstance().addServiceAddress(beanName, serviceAddressConfig); ???????????} ???????} ???}}代码比较简单，就是实现InitializingBean这个Spring接口，Spring启动在Bean创建后，初始化afterPropertiesSet（）这个配置，在这个方法里面读取类路径的配置文件。最后我们来运行一个例子。还是HelloService.我们有一个Invoker类，需要注入HelloService 对象调用。代码如下：
@Componentpublic class Invoker { ???@Autowired ???private HelloService helloService; ???@Resource(name = "helloService") ???private HelloService helloService2; ???public void print() { ???????helloService.hello("123"); ???????helloService2.hello("122344"); ???}}然后通过SpringBoot 启动测试：
@ComponentScan(basePackages = "com.qee.rpc")@EnableAutoConfigurationpublic class App { ???private static ExecutorService executorService = Executors.newCachedThreadPool(); ???private static final CountDownLatch cd = new CountDownLatch(1); ???public static void main(String[] args) { ???????try { ???????????SpringApplication.run(App.class, args); ???????????System.out.println("the main Thread :" + Thread.currentThread().getName()); ???????????final Invoker invoker = (Invoker) ApplicationContextUtils.getBean("invoker"); ???????????for (int i = 0; i < 300; i++) { ???????????????executorService.execute(new Runnable() { ???????????????????@Override ???????????????????public void run() { ???????????????????????try { ???????????????????????????cd.await(); ???????????????????????} catch (InterruptedException e) { ???????????????????????????e.printStackTrace(); ???????????????????????} ???????????????????????invoker.print(); ???????????????????} ???????????????}); ???????????} ???????????cd.countDown(); ???????????Thread.sleep(100000); ???????} catch (InterruptedException e) { ???????????e.printStackTrace(); ???????} finally { ???????????ExcuteManager.shutdown(); ???????????executorService.shutdown(); ???????} ???}有300个线程去调这个invoker.print();修改一下InterfaceProxyHandler的invoke方法，因为我们底层的通信还没完成。所以以
System.out.println("在InterfaceProxyHandler上调用invoke方法，参数是=" + args[0]);以这个语句来测试一下代码，其中这个大致框架已经上传到gitHub：https://github.com/vOoT/light-weight-rpc, 有什么建议和问题，大家一起讨论吧。最后贴一下执行结果：
哈哈哈，这样我们是不是就是可以通过Spring注解@Autowired 和 @Resource 来注入动态对象。
Netty自娱自乐之类Dubbo RPC 框架设计构想 【上篇】
原文地址：http://www.cnblogs.com/liferecord/p/7511617.html