https://my.oschina.net/huangyong/blog/361751
https://gitee.com/huangyong/rpc
在此文基础上的另一个实现，解决了原文中一些问题，增加了一些功能
http://www.cnblogs.com/luxiaoxun/p/5272384.html
这一类同时可以参考hadoop的实现，纯异步，相当于更进一步
http://www.cnblogs.com/LBSer/p/4853234.html (๑•̀ㅂ•́)و✧
第一个链接为作者的描述，非常清晰，第二个为代码，包含以下几个功能包
自己的理解和摘取一些我认为值得记录的点
RPC：客户端发起请求，端封装请求，网络连接到某个服务端（服务治理），通过网络协议（tcp/http），序列化请求发送到服务端，服务端收到网络请求，反序列化请求本地服务，再将返回序列化，发送到客户端，客户端反序列化给本地展示结果。
http应用层协议，tcp为传输层协议，越上层的协议可能提供了越丰富的特性，越底层数据传输越快。
JAVA本身的序列化方式不管是性能还是序列化后的字节大小都不太好，所以需要根据实际情况集成其他序列化方式
服务被部署在不同的服务器节点上，需要服务发现提供注册和客户端发现功能
如何实现？通过启动类加载xml文件，启动相关组件
public static void main(String[] args) {
new ClassPathXmlApplicationContext("spring.xml");
}
<!-- lang: xml -->
<beans ...>
<context:component-scan base-package="com.xxx.rpc.sample.server"/> <context:property-placeholder location="classpath:config.properties"/> <!-- 配置服务注册组件 -->
<bean id="serviceRegistry" class="com.xxx.rpc.registry.ServiceRegistry">
<constructor-arg name="registryAddress" value="${registry.address}"/>
</bean> <!-- 配置 RPC 服务器 -->
<bean id="rpcServer" class="com.xxx.rpc.server.RpcServer">
<constructor-arg name="serverAddress" value="${server.address}"/>
<constructor-arg name="serviceRegistry" ref="serviceRegistry"/>
</bean>
</beans>
服务注解标签
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Component // 表明可被 Spring 扫描
public @interface RpcService {
Class<?> value();
}
具体的服务实现类
@RpcService(HelloService.class) // 指定远程接口
public class HelloServiceImpl implements HelloService { @Override
public String hello(String name) {
return "Hello! " + name;
}
}
服务发现相关就是利用了zookeeper的znode/watcher
String ZK_REGISTRY_PATH = "/registry";
String ZK_DATA_PATH = ZK_REGISTRY_PATH + "/data";
public class ServiceRegistry {
private static final Logger LOGGER = LoggerFactory.getLogger(ServiceRegistry.class);
private CountDownLatch latch = new CountDownLatch(1);
private String registryAddress;
public ServiceRegistry(String registryAddress) {
this.registryAddress = registryAddress;
}
public void register(String data) {
if (data != null) {
ZooKeeper zk = connectServer();
if (zk != null) {
createNode(zk, data);
}
}
}
private ZooKeeper connectServer() {
ZooKeeper zk = null;
try {
zk = new ZooKeeper(registryAddress, Constant.ZK_SESSION_TIMEOUT, new Watcher() {
@Override
public void process(WatchedEvent event) {
if (event.getState() == Event.KeeperState.SyncConnected) {
latch.countDown();
}
}
});
latch.await();
} catch (IOException | InterruptedException e) {
LOGGER.error("", e);
}
return zk;
}
private void createNode(ZooKeeper zk, String data) {
try {
byte[] bytes = data.getBytes();
String path = zk.create(Constant.ZK_DATA_PATH, bytes, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
LOGGER.debug("create zookeeper node ({} => {})", path, data);
} catch (KeeperException | InterruptedException e) {
LOGGER.error("", e);
}
}
}
下面是NIO rpc的实现 implements ApplicationContextAware, InitializingBean
setApplicationContext处理类处理了注解指出的服务类
afterPropertiesSet 开启了服务并向注册中心注册
public class RpcServer implements ApplicationContextAware, InitializingBean {
private static final Logger LOGGER = LoggerFactory.getLogger(RpcServer.class);
private String serverAddress;
private ServiceRegistry serviceRegistry;
private Map<String, Object> handlerMap = new HashMap<>(); // 存放接口名与服务对象之间的映射关系
public RpcServer(String serverAddress) {
this.serverAddress = serverAddress;
}
public RpcServer(String serverAddress, ServiceRegistry serviceRegistry) {
this.serverAddress = serverAddress;
this.serviceRegistry = serviceRegistry;
}
@Override
public void setApplicationContext(ApplicationContext ctx) throws BeansException {
Map<String, Object> serviceBeanMap = ctx.getBeansWithAnnotation(RpcService.class); // 获取所有带有 RpcService 注解的 Spring Bean
if (MapUtils.isNotEmpty(serviceBeanMap)) {
for (Object serviceBean : serviceBeanMap.values()) {
String interfaceName = serviceBean.getClass().getAnnotation(RpcService.class).value().getName();
handlerMap.put(interfaceName, serviceBean);
}
}
}
@Override
public void afterPropertiesSet() throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap bootstrap = new ServerBootstrap();
bootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel channel) throws Exception {
channel.pipeline()
.addLast(new RpcDecoder(RpcRequest.class)) // 将 RPC 请求进行解码（为了处理请求）
.addLast(new RpcEncoder(RpcResponse.class)) // 将 RPC 响应进行编码（为了返回响应）
.addLast(new RpcHandler(handlerMap)); // 处理 RPC 请求
}
})
.option(ChannelOption.SO_BACKLOG, 128)
.childOption(ChannelOption.SO_KEEPALIVE, true);
String[] array = serverAddress.split(":");
String host = array[0];
int port = Integer.parseInt(array[1]);
ChannelFuture future = bootstrap.bind(host, port).sync();
LOGGER.debug("server started on port {}", port);
if (serviceRegistry != null) {
serviceRegistry.register(serverAddress); // 注册服务地址
}
future.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
}
public class RpcEncoder extends MessageToByteEncoder {
private Class<?> genericClass;
public RpcEncoder(Class<?> genericClass) {
this.genericClass = genericClass;
}
@Override
public void encode(ChannelHandlerContext ctx, Object in, ByteBuf out) throws Exception {
if (genericClass.isInstance(in)) {
byte[] data = SerializationUtil.serialize(in);
out.writeInt(data.length);
out.writeBytes(data);
}
}
}
请求
public class RpcRequest {
private String requestId;
private String className;
private String methodName;
private Class<?>[] parameterTypes;
private Object[] parameters;
// getter/setter...
}
响应
public class RpcResponse {
private String requestId;
private Throwable error;
private Object result;
// getter/setter...
}
这里将序列化和反序列化方法集中在序列化工具中，可以*替换成其他
public class SerializationUtil {
private static Map<Class<?>, Schema<?>> cachedSchema = new ConcurrentHashMap<>();
private static Objenesis objenesis = new ObjenesisStd(true);
private SerializationUtil() {
}
@SuppressWarnings("unchecked")
private static <T> Schema<T> getSchema(Class<T> cls) {
Schema<T> schema = (Schema<T>) cachedSchema.get(cls);
if (schema == null) {
schema = RuntimeSchema.createFrom(cls);
if (schema != null) {
cachedSchema.put(cls, schema);
}
}
return schema;
}
@SuppressWarnings("unchecked")
public static <T> byte[] serialize(T obj) {
Class<T> cls = (Class<T>) obj.getClass();
LinkedBuffer buffer = LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE);
try {
Schema<T> schema = getSchema(cls);
return ProtostuffIOUtil.toByteArray(obj, schema, buffer);
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
} finally {
buffer.clear();
}
}
public static <T> T deserialize(byte[] data, Class<T> cls) {
try {
T message = (T) objenesis.newInstance(cls);
Schema<T> schema = getSchema(cls);
ProtostuffIOUtil.mergeFrom(data, message, schema);
return message;
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
}
}
}
请求处理类handler，为了避免使用 Java 反射带来的性能问题，我们可以使用 CGLib 提供的反射 API，如下面用到的FastClass与FastMethod。
意思都一样，就是根据请求拿出请求相关信息，然后反射调用拿到结果构造返回
这里hadoop用的动态代理，跟这篇文章描述的这样 http://www.cnblogs.com/LBSer/p/4853234.html
public class RpcHandler extends SimpleChannelInboundHandler<RpcRequest> {
private static final Logger LOGGER = LoggerFactory.getLogger(RpcHandler.class);
private final Map<String, Object> handlerMap;
public RpcHandler(Map<String, Object> handlerMap) {
this.handlerMap = handlerMap;
}
@Override
public void channelRead0(final ChannelHandlerContext ctx, RpcRequest request) throws Exception {
RpcResponse response = new RpcResponse();
response.setRequestId(request.getRequestId());
try {
Object result = handle(request);
response.setResult(result);
} catch (Throwable t) {
response.setError(t);
}
ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
}
private Object handle(RpcRequest request) throws Throwable {
String className = request.getClassName();
Object serviceBean = handlerMap.get(className);
Class<?> serviceClass = serviceBean.getClass();
String methodName = request.getMethodName();
Class<?>[] parameterTypes = request.getParameterTypes();
Object[] parameters = request.getParameters();
/*Method method = serviceClass.getMethod(methodName, parameterTypes);
method.setAccessible(true);
return method.invoke(serviceBean, parameters);*/
FastClass serviceFastClass = FastClass.create(serviceClass);
FastMethod serviceFastMethod = serviceFastClass.getMethod(methodName, parameterTypes);
return serviceFastMethod.invoke(serviceBean, parameters);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
LOGGER.error("server caught exception", cause);
ctx.close();
}
}
客户端配置
<!-- lang: java -->
<beans ...>
<context:property-placeholder location="classpath:config.properties"/> <!-- 配置服务发现组件 -->
<bean id="serviceDiscovery" class="com.xxx.rpc.registry.ServiceDiscovery">
<constructor-arg name="registryAddress" value="${registry.address}"/>
</bean> <!-- 配置 RPC 代理 -->
<bean id="rpcProxy" class="com.xxx.rpc.client.RpcProxy">
<constructor-arg name="serviceDiscovery" ref="serviceDiscovery"/>
</bean>
</beans>
服务发现
public class ServiceDiscovery {
private static final Logger LOGGER = LoggerFactory.getLogger(ServiceDiscovery.class);
private CountDownLatch latch = new CountDownLatch(1);
private volatile List<String> dataList = new ArrayList<>();
private String registryAddress;
public ServiceDiscovery(String registryAddress) {
this.registryAddress = registryAddress;
ZooKeeper zk = connectServer();
if (zk != null) {
watchNode(zk);
}
}
public String discover() {
String data = null;
int size = dataList.size();
if (size > 0) {
if (size == 1) {
data = dataList.get(0);
LOGGER.debug("using only data: {}", data);
} else {
data = dataList.get(ThreadLocalRandom.current().nextInt(size));
LOGGER.debug("using random data: {}", data);
}
}
return data;
}
private ZooKeeper connectServer() {
ZooKeeper zk = null;
try {
zk = new ZooKeeper(registryAddress, Constant.ZK_SESSION_TIMEOUT, new Watcher() {
@Override
public void process(WatchedEvent event) {
if (event.getState() == Event.KeeperState.SyncConnected) {
latch.countDown();
}
}
});
latch.await();
} catch (IOException | InterruptedException e) {
LOGGER.error("", e);
}
return zk;
}
private void watchNode(final ZooKeeper zk) {
try {
List<String> nodeList = zk.getChildren(Constant.ZK_REGISTRY_PATH, new Watcher() {
@Override
public void process(WatchedEvent event) {
if (event.getType() == Event.EventType.NodeChildrenChanged) {
watchNode(zk);
}
}
});
List<String> dataList = new ArrayList<>();
for (String node : nodeList) {
byte[] bytes = zk.getData(Constant.ZK_REGISTRY_PATH + "/" + node, false, null);
dataList.add(new String(bytes));
}
LOGGER.debug("node data: {}", dataList);
this.dataList = dataList;
} catch (KeeperException | InterruptedException e) {
LOGGER.error("", e);
}
}
}
代理实现，构建服务请求信息，然后注册的服务里找一个，客户端netty将请求发送到服务端
public class RpcProxy {
private String serverAddress;
private ServiceDiscovery serviceDiscovery;
public RpcProxy(String serverAddress) {
this.serverAddress = serverAddress;
}
public RpcProxy(ServiceDiscovery serviceDiscovery) {
this.serviceDiscovery = serviceDiscovery;
}
@SuppressWarnings("unchecked")
public <T> T create(Class<?> interfaceClass) {
return (T) Proxy.newProxyInstance(
interfaceClass.getClassLoader(),
new Class<?>[]{interfaceClass},
new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
RpcRequest request = new RpcRequest(); // 创建并初始化 RPC 请求
request.setRequestId(UUID.randomUUID().toString());
request.setClassName(method.getDeclaringClass().getName());
request.setMethodName(method.getName());
request.setParameterTypes(method.getParameterTypes());
request.setParameters(args);
if (serviceDiscovery != null) {
serverAddress = serviceDiscovery.discover(); // 发现服务
}
String[] array = serverAddress.split(":");
String host = array[0];
int port = Integer.parseInt(array[1]);
RpcClient client = new RpcClient(host, port); // 初始化 RPC 客户端
RpcResponse response = client.send(request); // 通过 RPC 客户端发送 RPC 请求并获取 RPC 响应
if (response.isError()) {
throw response.getError();
} else {
return response.getResult();
}
}
}
);
}
}
客户端简单实现
public class RpcClient extends SimpleChannelInboundHandler<RpcResponse> {
private static final Logger LOGGER = LoggerFactory.getLogger(RpcClient.class);
private String host;
private int port;
private RpcResponse response;
private final Object obj = new Object();
public RpcClient(String host, int port) {
this.host = host;
this.port = port;
}
@Override
public void channelRead0(ChannelHandlerContext ctx, RpcResponse response) throws Exception {
this.response = response;
synchronized (obj) {
obj.notifyAll(); // 收到响应，唤醒线程
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
LOGGER.error("client caught exception", cause);
ctx.close();
}
public RpcResponse send(RpcRequest request) throws Exception {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(group).channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel channel) throws Exception {
channel.pipeline()
.addLast(new RpcEncoder(RpcRequest.class)) // 将 RPC 请求进行编码（为了发送请求）
.addLast(new RpcDecoder(RpcResponse.class)) // 将 RPC 响应进行解码（为了处理响应）
.addLast(RpcClient.this); // 使用 RpcClient 发送 RPC 请求
}
})
.option(ChannelOption.SO_KEEPALIVE, true);
ChannelFuture future = bootstrap.connect(host, port).sync();
future.channel().writeAndFlush(request).sync();
synchronized (obj) {
obj.wait(); // 未收到响应，使线程等待
}
if (response != null) {
future.channel().closeFuture().sync();
}
return response;
} finally {
group.shutdownGracefully();
}
}
}
客户端发送测试
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:spring.xml")
public class HelloServiceTest { @Autowired
private RpcProxy rpcProxy; @Test
public void helloTest() {
HelloService helloService = rpcProxy.create(HelloService.class);
String result = helloService.hello("World");
Assert.assertEquals("Hello! World", result);
}
}