这篇文章主要介绍“怎么使用Netty实现类似Dubbo的远程接口调用”的相关知识，小编通过实际案例向大家展示操作过程，操作方法简单快捷，实用性强，希望这篇“怎么使用Netty实现类似Dubbo的远程接口调用”文章能帮助大家解决问题。
一、Netty简介
Netty 是一个基于NIO的客户、服务器端的编程框架，使用Netty 可以确保你快速和简单的开发出一个网络应用，例如实现了某种协议的客户、服务端应用。Netty相当于简化和流线化了网络应用的编程开发过程，例如：基于TCP和UDP的socket服务开发。
实现步骤：
创建接口和实现类
创建客户端代码
通过动态代理模式，封装netty远程接口调用
通过异步线程等待/通知，实现异步转同步
创建服务端代码
自定义编码解码器
编写测试客户端发送请求代码
二、完整代码实现
工程依赖引入
<dependency> <groupId>io.netty</groupId> <artifactId>netty-all</artifactId> <version>4.1.75.Final</version> </dependency>
1、创建接口和实现类
定义简单接口和实现类。通过注解定义接口和服务实现，在后续代码中解析注解。
@ServiceEntry定义接口serviceId
@MyService定义服务实现类
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 {
/**
* 服务Id
*/
String serviceId();
/**
* 服务名称
*/
String name() default "";
}
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyService {
String value() default "";
}2、客户端代码实现及动态代理和异步转同步
1）创建客户端Handler，MyClientHandler，继承ChannelInboundHandlerAdapter，并实现Callable接口
客户端发送请求时，会调用call方法，在这里将异步转同步
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
收到服务端返回时，设置返回结果数据，并通知线程执行
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;
}
}2）创建客户端代码，MyClient
通过动态代理，包装远程服务请求
初始化服务端链接，通过双检锁确保clientHandler是单例实现
发送请求时，通过线程池异步发送clientHandler
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();
}
}
}3、服务端代码实现
1）创建服务工程类ServiceFacatory，解析注解保存服务接口和实现类，调用的时候从Map直接获取
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;
}2）包解析工具类，解析指定目录下的所有service类
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 = "**/*.class";
/**
* 结合spring的类扫描方式
* 根据需要扫描的包路径及相应的注解，获取最终测method集合
* 仅返回public方法，如果方法是非public类型的，不会被返回
* 可以扫描工程下的class文件及jar中的class文件
*
* @param scanPackages
* @param annotation
* @return
*/
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;
}
/**
* 根据扫描包的,查询下面的所有类
*
* @param scanPackages 扫描的package路径
* @return
*/
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;
}
/**
* 排重、检测package父子关系，避免多次扫描
*
* @param scanPackages
* @return 返回检查后有效的路径集合
*/
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;
}
/**
* 加载资源，根据resource获取className
*
* @param metadataReaderFactory spring中用来读取resource为class的工具
* @param resource 这里的资源就是一个Class
*/
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();
}
}3）创建服务端Handler类，接收客户端请求，并调用服务实现类执行接口
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());
}
}4）创建服务端启动类MyServer、ServerApp，启动端口监听；加入编解码器和服务端MyServerHandler
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);
}
}4、自定义编码解码器
1）创建请求数据编解码器RequestMessageCodec，实现String和请求参数对象RequestData之间互相转换
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&