服務器端與客戶端都要用到：

public interface ZkInfo {String ZK_CONNECTION_STRING = "192.168.1.201:2181,192.168.1.202:2181,192.168.1.203:2181";int ZK_SESSION_TIMEOUT = 5000;String ZK_REGISTRY_PATH = "/registry";String ZK_PROVIDER_PATH = ZK_REGISTRY_PATH + "/provider"; } import java.rmi.Remote; import java.rmi.RemoteException;public interface MyService extends Remote {String showInfo(String name) throws RemoteException; }

服務器端

import java.net.Inet4Address; import java.net.InetAddress; import java.net.UnknownHostException; import java.rmi.RemoteException; import java.rmi.server.UnicastRemoteObject; import java.util.Calendar;public class MyServiceImpl extends UnicastRemoteObject implements MyService{/*** */private static final long serialVersionUID = 8329425460319055273L;protected MyServiceImpl() throws RemoteException {}public String showInfo(String name) throws RemoteException {String h = "";try {InetAddress host = Inet4Address.getLocalHost();h = host.getHostAddress();} catch (UnknownHostException e) {// TODO Auto-generated catch blocke.printStackTrace();}Calendar c = Calendar.getInstance();return h + " " + c.getTime().toString() + name;}}

import java.io.IOException; import java.net.MalformedURLException; import java.rmi.Naming; import java.rmi.Remote; import java.rmi.RemoteException; import java.rmi.registry.LocateRegistry; import java.util.concurrent.CountDownLatch;import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooDefs; import org.apache.zookeeper.ZooKeeper; import org.slf4j.Logger; import org.slf4j.LoggerFactory;public class ServiceProvider {private static final Logger LOGGER = LoggerFactory.getLogger(ServiceProvider.class);//用於等待SyncConnected事件觸發後繼續執行當前進程private CountDownLatch latch = new CountDownLatch(1);//發佈RMI服務並註冊RMI地址到ZooKeeper中public void publish(Remote remote, String host, int port){String url = publishService(remote, host, port);//發佈RMI服務並返回RMI地址if (url != null){ZooKeeper zk = connectServer();//連接ZooKeeper服務器並獲取ZooKeeper對象if (zk != null){createNode(zk, url); //創建ZNode並將RMI地址放入ZNode上}}}//發佈RMI服務private String publishService(Remote remote, String host, int port){String url = null;try{url = String.format("rmi://%s:%d/%s", host, port, remote.getClass().getName());LocateRegistry.createRegistry(port);Naming.rebind(url, remote);LOGGER.debug("publish rmi service(url: {})", url);} catch(RemoteException | MalformedURLException e) {LOGGER.error("", e);}return url;}//連接ZooKeeper服務器private ZooKeeper connectServer(){ZooKeeper zk = null;try{zk = new ZooKeeper(ZkInfo.ZK_CONNECTION_STRING, ZkInfo.ZK_SESSION_TIMEOUT, new Watcher(){@Overridepublic void process(WatchedEvent event){if (event.getState() == Event.KeeperState.SyncConnected){latch.countDown();//喚醒當前正在執行的線程}}});if (zk.exists(ZkInfo.ZK_REGISTRY_PATH, false) == null)zk.create(ZkInfo.ZK_REGISTRY_PATH, " ".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);latch.await(); //使當前進程處於等待狀態} catch (IOException | InterruptedException | KeeperException e){LOGGER.error("", e);}return zk;}//創建ZNodeprivate void createNode(ZooKeeper zk, String url){try{byte[] data = url.getBytes();//創建一個臨時性且有序的ZNodeString path = zk.create(ZkInfo.ZK_PROVIDER_PATH, data, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);LOGGER.debug("create zookeeper node ({} => {})", path, url);} catch (KeeperException | InterruptedException e){LOGGER.error("", e);}} }

//ZooKeeper版本 public class Server {public static void main(String[] args) throws Exception{if (args.length != 2){System.err.println("please using command: java Server <rmi_host> <rmi_port>");System.exit(-1);}String host = args[0];int port = Integer.parseInt(args[1]);ServiceProvider provider = new ServiceProvider();MyServiceImpl myService = new MyServiceImpl();provider.publish(myService, host, port);Thread.sleep(Long.MAX_VALUE);} }
import java.rmi.Naming; import java.rmi.registry.LocateRegistry;//無ZooKeeper版本 public class RmiServer {public static void main(String[] args) throws Exception{int port = 1099;String url = "rmi://localhost:1099/MyServiceImpl";LocateRegistry.createRegistry(port);Naming.rebind(url, new MyServiceImpl());} }
客戶端

import java.io.IOException; import java.net.MalformedURLException; import java.rmi.ConnectException; import java.rmi.Naming; import java.rmi.NotBoundException; import java.rmi.Remote; import java.rmi.RemoteException; import java.util.ArrayList; import java.util.List; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ThreadLocalRandom;import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import org.slf4j.Logger; import org.slf4j.LoggerFactory;public class ServiceConsumer {private static final Logger LOGGER = LoggerFactory.getLogger(ServiceConsumer.class);//用於等待SyncConnected事件觸發後繼續執行當前進程private CountDownLatch latch = new CountDownLatch(1);// 定義一個 volatile 成員變量，用于保存最新的 RMI 地址（考慮到該變量或許會被其它線程所修改，一旦修改后，該變量的值會影響到所有線程）// volatile讓變量每次在使用的時候，都從主存中取。而不是從各個線程的“工作內存”。// volatile具有synchronized關鍵字的“可見性”，但是沒有synchronized關鍵字的“并發正確性”，也就是說不保證線程執行的有序性。// 也就是說，volatile變量對于每次使用，線程都能得到當前volatile變量的最新值。但是volatile變量并不保證并發的正確性。private volatile List<String> urlList = new ArrayList<>();//連接ZooKeeper服務器private ZooKeeper connectServer(){ZooKeeper zk = null;try {zk = new ZooKeeper(ZkInfo.ZK_CONNECTION_STRING, ZkInfo.ZK_SESSION_TIMEOUT, new Watcher(){@Overridepublic void process(WatchedEvent event){if (event.getState() == Event.KeeperState.SyncConnected){latch.countDown();//喚醒當前正在執行的線程}}});latch.await();//使當前線程處於等待狀態} catch (IOException | InterruptedException e){LOGGER.error("", e);}return zk;}//觀察/registry節點下所有子節點是否有變化private void watchNode(final ZooKeeper zk){try{List<String> nodeList = zk.getChildren(ZkInfo.ZK_REGISTRY_PATH, new Watcher(){@Overridepublic void process(WatchedEvent event){if (event.getType() == Event.EventType.NodeChildrenChanged){watchNode(zk);//若子節點有變化，則重新調用該方法（爲了獲取最新子節點中的數據）}}});List<String> dataList = new ArrayList<>();//用於存放/registry所有子節點中的 數據for (String node : nodeList){byte[] data = zk.getData(ZkInfo.ZK_REGISTRY_PATH + "/" + node, false, null); //獲取/registry的子節點中的數據dataList.add(new String(data));}LOGGER.debug("node data: {}", dataList);urlList = dataList; // 更新最新的 RMI 地址} catch (KeeperException | InterruptedException e){LOGGER.error("", e);}}//構造器public ServiceConsumer(){ZooKeeper zk = connectServer();//連接ZooKeeper服務器並獲取ZooKeeper對象if (zk != null){watchNode(zk);//觀察/registry節點的所有子節點並更新urlList成員變量}}//在JNDI中查找RMI遠程服務對象@SuppressWarnings("unchecked")private <T> T lookupService(String url){T remote = null;try{remote = (T) Naming.lookup(url);} catch (NotBoundException | MalformedURLException | RemoteException e){if ( e instanceof ConnectException){//若連接中斷，則使用urlList中第一個RMI地址來查找(這是一種簡單的重試方式，確保不會拋出異常)LOGGER.error("ConnectException -> url: {}", url);if (urlList.size() != 0){url = urlList.get(0);return lookupService(url);}}LOGGER.error("", e);}return remote;}//查找RMI服務public <T extends Remote> T lookup(){T service = null;int size = urlList.size();if (size > 0){String url;if (size == 1){url = urlList.get(0); //若urlList中只有一個元素，則直接獲取該元素LOGGER.debug("using only url: {}", url);} else {url = urlList.get(ThreadLocalRandom.current().nextInt(size));//若urlList中存在多個元素，則隨機獲取一個元素LOGGER.debug("using random url: {}", url);System.out.println(url);}service = lookupService(url);}return service;} }
//含ZooKeeper版本 public class Client {public static void main(String[] args) throws Exception{ServiceConsumer consumer = new ServiceConsumer();//zookeeper測試while (true){MyService myService = consumer.lookup();String result = myService.showInfo("test");System.out.println(result);Thread.sleep(3000);}} }
import java.rmi.Naming;//無ZooKeeper版本 public class RmiClient {public static void main(String[] args) throws Exception{String url = "rmi://localhost:1099/MyServiceImpl";MyService myService = (MyService)Naming.lookup(url);String result = myService.showInfo("jinzhao");System.out.println(result);} }

log4j.properties

# Define some default values that can be overridden by system properties zookeeper.root.logger=INFO, CONSOLE zookeeper.console.threshold=INFO zookeeper.log.dir=. zookeeper.log.file=zookeeper.log zookeeper.log.threshold=DEBUG zookeeper.tracelog.dir=. zookeeper.tracelog.file=zookeeper_trace.log# # ZooKeeper Logging Configuration ## Format is "<default threshold> (, <appender>)+# DEFAULT: console appender only log4j.rootLogger=${zookeeper.root.logger}# Example with rolling log file #log4j.rootLogger=DEBUG, CONSOLE, ROLLINGFILE# Example with rolling log file and tracing #log4j.rootLogger=TRACE, CONSOLE, ROLLINGFILE, TRACEFILE# # Log INFO level and above messages to the console # log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender log4j.appender.CONSOLE.Threshold=${zookeeper.console.threshold} log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L] - %m%n# # Add ROLLINGFILE to rootLogger to get log file output # Log DEBUG level and above messages to a log file log4j.appender.ROLLINGFILE=org.apache.log4j.RollingFileAppender log4j.appender.ROLLINGFILE.Threshold=${zookeeper.log.threshold} log4j.appender.ROLLINGFILE.File=${zookeeper.log.dir}/${zookeeper.log.file}# Max log file size of 10MB log4j.appender.ROLLINGFILE.MaxFileSize=10MB # uncomment the next line to limit number of backup files #log4j.appender.ROLLINGFILE.MaxBackupIndex=10log4j.appender.ROLLINGFILE.layout=org.apache.log4j.PatternLayout log4j.appender.ROLLINGFILE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L] - %m%n# # Add TRACEFILE to rootLogger to get log file output # Log DEBUG level and above messages to a log file log4j.appender.TRACEFILE=org.apache.log4j.FileAppender log4j.appender.TRACEFILE.Threshold=TRACE log4j.appender.TRACEFILE.File=${zookeeper.tracelog.dir}/${zookeeper.tracelog.file}log4j.appender.TRACEFILE.layout=org.apache.log4j.PatternLayout ### Notice we are including log4j's NDC here (%x) log4j.appender.TRACEFILE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L][%x] - %m%n

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