使用Netty实现类似Dubbo的远程接口调用的实现方法

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.75.Final</version>
</dependency>

public interface IHelloService {
    @ServiceEntry(serviceId = "001", name = "hello")
    String hello(String msg);
}
@MyService
public class HelloServiceImpl implements IHelloService {
    @Override
    public String hello(String msg) {
        return "re:这里是服务端，已收到客户端消息:" + msg.hashCode();
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface ServiceEntry {
    
    String serviceId();

    
    String name() default "";
}
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyService {
    String value() default "";
}

public class MyClientHandler extends ChannelInboundHandlerAdapter implements Callable<String> {
    private ChannelHandlerContext ctx;
    private ConcurrentHashMap<String, SyncSendContext> syncSendContextMap = new ConcurrentHashMap<>();
    private Object[] param;
    private String serviceId;
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("客户端和服务端链接成功");
        this.ctx = ctx;
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("客户端收到服务端回复: " + msg);
        ResponseData data = (ResponseData) msg;
        String id = data.getId();
        // 收到服务端返回时，设置返回结果数据，并通知线程执行
        SyncSendContext context = syncSendContextMap.get(id);
        context.setResp(data);
        synchronized (context) {
            context.notify();
        }
    }
    @Override
    public String call() throws Exception {
        System.out.println("客户端向服务端发送消息: " + param[0].toString());
        String id = UUID.randomUUID().toString();
        RequestData data = new RequestData();
        data.setId(id);
        //强制设置参数1
        data.setData(param[0].toString());
        data.setServiceId(serviceId);
        SyncSendContext context = new SyncSendContext();
        context.setRequest(data);
        // 将请求context放入map，并等待线程，在收到服务端返回时，异步通知线程执行，返回结果数据
        syncSendContextMap.put(id, context);
        synchronized (context) {
            ctx.writeAndFlush(data);
            context.wait();
            return (String) context.getResp().getData();
        }
    }
    public void setParam(Object[] param) {
        this.param = param;
    }
    public void setServiceId(String serviceId) {
        this.serviceId = serviceId;
    }
}

public class MyClient {
    private static ExecutorService executor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
    private MyClientHandler clientHandler;
    // 通过动态代理，包装远程服务请求
    public <T> T getServie(final Class<T> service) {
        return (T) Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), new Class<?>[]{service},
                (proxy, method, args) -> {
                    if (clientHandler == null) {
                        init("127.0.0.1", 7000);
                    }
                    ServiceEntry annotation = method.getAnnotation(ServiceEntry.class);
                    if (annotation == null) {
                        return null;
                    }
                    clientHandler.setParam(args);
                    clientHandler.setServiceId(annotation.serviceId());
                    return executor.submit(clientHandler).get();
                });
    }
    // 初始化服务端链接，通过双检锁确保clientHandler是单例实现
    private synchronized void init(String hostname, int port) {
        if (clientHandler != null) {
            return;
        }
        clientHandler = new MyClientHandler();
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap().group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.SO_KEEPALIVE, true)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new StringDecoder());
                            pipeline.addLast(new StringEncoder());
                            pipeline.addLast(new ResponseMessageCodec());
                            pipeline.addLast(new RequestMessageCodec());
                            pipeline.addLast(clientHandler);
                        }
                    });
            bootstrap.connect(hostname, port).sync();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class ServiceFacatory {
    private static final Map<String, Method> methodMap = new HashMap<>();
    private static final Map<String, Object> serviceMap = new HashMap<>();
    public static void init() throws Exception {
        // 要扫描的包
        String packages = "com.hj.netty.dubbo.api";
        Set<MethodInfo> methods = PackageUtils.findClassAnnotationMethods(packages, ServiceEntry.class);
        for (MethodInfo info : methods) {
            ServiceEntry serviceEntry = (ServiceEntry) info.getAnnotation();
            methodMap.put(serviceEntry.serviceId(), info.getMethod());
            String serviceName = info.getMethod().getDeclaringClass().getName();
            if (!serviceMap.containsKey(serviceName)) {
                Object instance = info.getMethod().getDeclaringClass().newInstance();
                serviceMap.put(serviceName, instance);
            }
        }
    }
    public static Object invoke(String serviceId, Object args) throws Exception {
        Method method = methodMap.get(serviceId);
        String serviceName = method.getDeclaringClass().getName();
        Object instance = serviceMap.get(serviceName);
        Object result = method.invoke(instance, args);
        return result;
    }
}
@Data
@AllArgsConstructor
public class MethodInfo {
    private Annotation annotation;
    private Method method;
}

import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.util.SystemPropertyUtils;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Parameter;
import java.util.*;
public class PackageUtils {
    private final static Logger log = LoggerFactory.getLogger(PackageUtils.class);
    //扫描  scanPackages 下的文件的匹配符
    protected static final String DEFAULT_RESOURCE_PATTERN = "**
    public static Set<MethodInfo> findClassAnnotationMethods(String scanPackages, Class<? extends Annotation> annotation) {
        //获取所有的类
        Set<String> clazzSet = findPackageClass(scanPackages);
        Set<MethodInfo> methods = new HashSet<>();
        //遍历类，查询相应的annotation方法
        for (String clazz : clazzSet) {
            try {
                Set<MethodInfo> ms = findAnnotationMethods(clazz, annotation);
                methods.addAll(ms);
            } catch (ClassNotFoundException ignore) {
            }
        }
        return methods;
    }
    public static Set<MethodInfo> findAnnotationMethods(String fullClassName, Class<? extends Annotation> anno) throws ClassNotFoundException {
        Set<MethodInfo> methodSet = new HashSet<>();
        Class<?> clz = Class.forName(fullClassName);
        // 存储接口中定义的方法
        Map<String, Method> mapMethodInf = new HashMap<>();
        for (int i = 0; i < clz.getInterfaces().length; i++) {
            Class<?> inf = clz.getInterfaces()[i];
            Method[] methods = inf.getDeclaredMethods();
            for (Method method : methods) {
                String key = getMethodKey(method);
                mapMethodInf.put(key, method);
            }
        }
        Method[] methods = clz.getDeclaredMethods();
        for (Method method : methods) {
            if (method.getModifiers() != Modifier.PUBLIC) {
                continue;
            }
            Annotation annotation = method.getAnnotation(anno);
            if (annotation != null) {
                methodSet.add(new MethodInfo(annotation,method));
            } else {
                // 从接口中读取对应的方法
                String key = getMethodKey(method);
                Method methodInf = mapMethodInf.get(key);
                annotation = methodInf.getAnnotation(anno);
                if (annotation != null) {
                    methodSet.add(new MethodInfo(annotation,method));
                }
            }
        }
        return methodSet;
    }
    
    private static Set<String> findPackageClass(String scanPackages) {
        if (StringUtils.isBlank(scanPackages)) {
            return Collections.EMPTY_SET;
        }
        //验证及排重包路径,避免父子路径多次扫描
        Set<String> packages = checkPackage(scanPackages);
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(resourcePatternResolver);
        Set<String> clazzSet = new HashSet<String>();
        for (String basePackage : packages) {
            if (StringUtils.isBlank(basePackage)) {
                continue;
            }
            String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                    org.springframework.util.ClassUtils.convertClassNameToResourcePath(SystemPropertyUtils.resolvePlaceholders(basePackage)) + "/" + DEFAULT_RESOURCE_PATTERN;
            try {
                Resource[] resources = resourcePatternResolver.getResources(packageSearchPath);
                for (Resource resource : resources) {
                    //检查resource，这里的resource都是class
                    String clazz = loadClassName(metadataReaderFactory, resource);
                    clazzSet.add(clazz);
                }
            } catch (Exception e) {
                log.error("获取包下面的类信息失败,package:" + basePackage, e);
            }
        }
        return clazzSet;
    }
    
    private static Set<String> checkPackage(String scanPackages) {
        if (StringUtils.isBlank(scanPackages)) {
            return Collections.EMPTY_SET;
        }
        Set<String> packages = new HashSet<>();
        //排重路径
        Collections.addAll(packages, scanPackages.split(","));
        String[] strings = packages.toArray(new String[packages.size()]);
        for (String pInArr : strings) {
            if (StringUtils.isBlank(pInArr) || pInArr.equals(".") || pInArr.startsWith(".")) {
                continue;
            }
            if (pInArr.endsWith(".")) {
                pInArr = pInArr.substring(0, pInArr.length() - 1);
            }
            Iterator<String> packageIte = packages.iterator();
            boolean needAdd = true;
            while (packageIte.hasNext()) {
                String pack = packageIte.next();
                if (pInArr.startsWith(pack + ".")) {
                    //如果待加入的路径是已经加入的pack的子集，不加入
                    needAdd = false;
                } else if (pack.startsWith(pInArr + ".")) {
                    //如果待加入的路径是已经加入的pack的父集，删除已加入的pack
                    packageIte.remove();
                }
            }
            if (needAdd) {
                packages.add(pInArr);
            }
        }
        return packages;
    }
    
    private static String loadClassName(MetadataReaderFactory metadataReaderFactory, Resource resource) {
        try {
            if (resource.isReadable()) {
                MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(resource);
                if (metadataReader != null) {
                    return metadataReader.getClassMetadata().getClassName();
                }
            }
        } catch (Exception e) {
            log.error("根据resource获取类名称失败", e);
        }
        return null;
    }
    private static String getMethodKey(Method method) {
        StringBuilder key = new StringBuilder(method.getName());
        for (Parameter parameter : method.getParameters()) {
            key.append(parameter.getType().getName())
                    .append(parameter.getName());
        }
        return key.toString();
    }
}

public class MyServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("客户端接入");
        super.channelActive(ctx);
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("收到客户端消息:" + msg);
        RequestData req = (RequestData) msg;
        if (req != null) {
            String args = req.getData();
            String serviceId = req.getServiceId();
            // 调用服务实现类
            Object res = ServiceFacatory.invoke(serviceId, args);
            ResponseData resp = new ResponseData();
            resp.setData(res);
            resp.setId(req.getId());
            ctx.writeAndFlush(resp);
        }
        System.out.println("----------响应结束----------" + req.getData());
    }
}

public class MyServer {
    public static void start(String hostname, int port) throws Exception {
        ServiceFacatory.init();
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap().group(bossGroup, workGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .option(ChannelOption.SO_KEEPALIVE, true)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new StringDecoder());
                            pipeline.addLast(new StringEncoder());
                            pipeline.addLast(new RequestMessageCodec());
                            pipeline.addLast(new ResponseMessageCodec());
                            pipeline.addLast(new MyServerHandler());
                        }
                    });
            ChannelFuture future = bootstrap.bind(hostname, port).sync();
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }
}
public class ServerApp {
    public static void main(String[] args) throws Exception {
        MyServer.start("127.0.0.1", 7000);
    }
}

public class RequestMessageCodec extends MessageToMessageCodec<String, RequestData> {
    @Override
    protected void encode(ChannelHandlerContext ctx, RequestData msg, List<Object> out) throws Exception {
        System.out.println("RequestMessageCodec.encode 被调用 " + msg);
        String json = JSONObject.toJSONString(msg);
        out.add(json);
    }
    @Override
    protected void decode(ChannelHandlerContext ctx, String msg, List<Object> out) throws Exception {
        System.out.println("RequestMessageCodec.decode 被调用 " + msg);
        RequestData po = JSONObject.parseObject(msg, RequestData.class);
        out.add(po);
    }
}

public class ResponseMessageCodec extends MessageToMessageCodec<String, ResponseData> {
    @Override
    protected void encode(ChannelHandlerContext ctx, ResponseData msg, List<Object> out) throws Exception {
        System.out.println("ResponseMessageCodec.encode 被调用 " + msg);
        String json = JSONObject.toJSONString(msg);
        out.add(json);
    }
    @Override
    protected void decode(ChannelHandlerContext ctx, String msg, List<Object> out) throws Exception {
        System.out.println("ResponseMessageCodec.decode 被调用 " + msg);
        ResponseData po = JSONObject.parseObject(msg, ResponseData.class);
        out.add(po);
    }
}

@Data
public class RequestData {
    private String id;
    private String serviceId;
    private String data;
}
@Data
public class ResponseData {
    private String id;
    private Object data;
}
@Data
public class SyncSendContext {
    private ResponseData resp;
    private RequestData request;
}

public class ClientTest {
    public static void main(String[] args) throws Exception {
        MyClient client = new MyClient();
        IHelloService servie = client.getServie(IHelloService.class);
        for (int i = 0; i < 5; i++) {
            Thread.sleep(2 * 1000);
            String res = servie.hello("你好 服务端 ~~ " + i);
            System.out.println("service 得到服务端返回消息: " + res);
            System.out.println("-----------------------------" + i +" 结束");
        }
    }
}