基于netty实现rpc框架-spring boot客户端

上篇讲了RPC服务端的实现。原理就是解析netty通道数据拿到类、方法及入参等信息，然后通过java反射机制调用本地接口返回结果。没有用到很复杂的技术。

这篇我们将客户端的实现。说白了客户端的任务很简单：一是建立socket长连接。二是封装发送服务端需要的数据包。三是处理返回结果。

demo地址

https://gitee.com/syher/grave-netty

RPC实现

同样定义注解扫描service接口。

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({NettyClientScannerRegistrar.class, NettyClientApplicationContextAware.class})
public @interface NettyClientScan {

    String[] basePackages();

    Class factoryBean() default NettyFactoryBean.class;
}

　　

该注解用于spring boot启动类上，参数basePackages指定接口所在的包路径。

@SpringBootApplication
@NettyClientScan(basePackages = {
        "com.braska.grave.netty.api.service"
})
public class GraveNettyClientApplication {

    public static void main(String[] args) {
        SpringApplication.run(GraveNettyClientApplication.class, args);
    }

}

　　

NettyServerScannerRegistrar类注册bean。

public class NettyClientScannerRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware {

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        // spring bean注册
        NettyClientInterfaceScanner scanner = new NettyClientInterfaceScanner(registry);

        AnnotationAttributes annoAttrs =
                AnnotationAttributes.fromMap(importingClassMetadata.getAnnotationAttributes(NettyClientScan.class.getName()));

        Class nettyFactoryBeanClass = annoAttrs.getClass("factoryBean");
        if (!NettyFactoryBean.class.equals(nettyFactoryBeanClass)) {
            scanner.setNettyFactoryBean(BeanUtils.instantiateClass(nettyFactoryBeanClass));
        }

        List basePackages = new ArrayList();
        for (String pkg : annoAttrs.getStringArray("basePackages")) {
            if (StringUtils.hasText(pkg)) {
                basePackages.add(pkg);
            }
        }

        scanner.doScan(StringUtils.toStringArray(basePackages));
    }
}

　　

NettyClientInterfaceScanner类使用jdk动态代理basePackages路径下的接口。

public class NettyClientInterfaceScanner extends ClassPathBeanDefinitionScanner {
    private NettyFactoryBean nettyFactoryBean = new NettyFactoryBean();


    @Override
    public Set doScan(String... basePackages) {
        Set beanDefinitions = super.doScan(basePackages);

        if (beanDefinitions.isEmpty()) {
        } else {
            processBeanDefinitions(beanDefinitions);
        }

        return beanDefinitions;
    }

    private void processBeanDefinitions(
            Set beanDefinitions) {

        GenericBeanDefinition definition;

        for (BeanDefinitionHolder holder : beanDefinitions) {

            definition = (GenericBeanDefinition) holder.getBeanDefinition();
            // 为对象属性赋值（这一块我也还不太明白）
　　　　　　　definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName());
            // 这里的nettyFactoryBean是生成Bean实例的工厂，不是Bean本身
            definition.setBeanClass(this.nettyFactoryBean.getClass());

            definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
        }
    }
}

　　

NettyFactoryBean 

public class NettyFactoryBean implements FactoryBean {
    private Class nettyInterface;

    public NettyFactoryBean() {}

    public NettyFactoryBean(Class nettyInterface) {
        this.nettyInterface = nettyInterface;
    }

    @Override
    public T getObject() throws Exception {
        // 通过jdk动态代理创建实例
        return (T) Proxy.newProxyInstance(nettyInterface.getClassLoader(), new Class[]{nettyInterface}, c.getInstance());
    }

    @Override
    public Class getObjectType() {
        return this.nettyInterface;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

　　

关键来了，NettyInterfaceInvoker类负责数据包封装及发送。

public class NettyInterfaceInvoker implements InvocationHandler {

    private RequestSender sender;
    // 静态内部类做单例模式 
    private static class SINGLETON {
        private static final NettyInterfaceInvoker invoker = new NettyInterfaceInvoker();

        private static NettyInterfaceInvoker setSender(RequestSender sender) {
            invoker.sender = sender;
            return invoker;
        }
    }

    public static NettyInterfaceInvoker getInstance() {
        return SINGLETON.invoker;
    }

    public static NettyInterfaceInvoker setSender(RequestSender sender) {
        return SINGLETON.setSender(sender);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 数据包封装，包含类名、方法名及参数等信息。
        Request request = new Request();
        request.setClassName(method.getDeclaringClass().getName());
        request.setMethodName(method.getName());
        request.setParameters(args);
        request.setParameterTypes(method.getParameterTypes());
        request.setId(UUID.randomUUID().toString());
        // 数据发送
        Object result = sender.send(request);
        Class returnType = method.getReturnType();
        // 处理返回数据
        Response response = JSON.parseObject(result.toString(), Response.class);
        if (response.getCode() == 1) {
            throw new Exception(response.getError());
        }
        if (returnType.isPrimitive() || String.class.isAssignableFrom(returnType)) {
            return response.getData();
        } else if (Collection.class.isAssignableFrom(returnType)) {
            return JSONArray.parseArray(response.getData().toString(), Object.class);
        } else if (Map.class.isAssignableFrom(returnType)) {
            return JSON.parseObject(response.getData().toString(), Map.class);
        } else {
            Object data = response.getData();
            return JSONObject.parseObject(data.toString(), returnType);
        }
    }
}

　　

接着我们来看看RequestSender怎么处理数据的。

public interface RequestSender {
    Channel connect(SocketAddress address) throws InterruptedException;

    Object send(Request request) throws InterruptedException;
}

　　

RequestSender本身只是一个接口。他的实现类有：

public class NettyClientApplicationContextAware extends ChannelInitializer
        implements RequestSender, ApplicationContextAware, InitializingBean {
    private static final Logger logger = Logger.getLogger(NettyClientApplicationContextAware.class.getName());

    private String remoteAddress;
    private Bootstrap bootstrap;
    private EventLoopGroup group;
    private NettyChannelManager manager;
    private NettyClientHandler handler;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.remoteAddress = applicationContext.getEnvironment().getProperty("remoteAddress");
        this.bootstrap = new Bootstrap();
        this.group = new NioEventLoopGroup(1);
        this.bootstrap.group(group).
                channel(NioSocketChannel.class).
                option(ChannelOption.TCP_NODELAY, true).
                option(ChannelOption.SO_KEEPALIVE, true).
                handler(this);
        this.manager = new NettyChannelManager(this);
        this.handler = new NettyClientHandler(manager, remoteAddress);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // socket连接入口。
        this.manager.refresh(Lists.newArrayList(remoteAddress));
    }

    @Override
    public Object send(Request request) throws InterruptedException {
        Channel channel = manager.take();
        if (channel != null && channel.isActive()) {
            SynchronousQueue