RMI/WebService冗余服务器的通用客户端。
需求:
企业应用要有有redundancy,两台或者多台服务器提供HA(Highavailable)服务,提供热备用。服务一般是EJB/RMI/WebService等服务,在一台发生服务故障后,客户端一般自动切换到其它可用服务器,所有服务器都依次fail后才报错。
EJB也应该适用,但是一般EJB容器都提供了更完善的HA机制和策略。这里不cover.
不足和限制:
1.暂时没有考虑内网/外网优先顺序。
2.使用接口+javaproxy实现拦截,接口必须。
3.webservice使用动态绑定。
4.一台失败后,遍历所有服务器,故障服务器没有排除
5.java6以上测试通过
6.通信失败的检测不见得完善
7.WebService采用POJO发布,要求Port和Service名称和接口名称相同,便于简化查找。建议定义为常量。
测试服务代码(同时提供rmi/ws服务):
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package org.steeven.remote; import java.rmi.Remote; import java.rmi.RemoteException; import javax.jws.WebService; import javax.jws.soap.SOAPBinding; @WebService(targetNamespace = Hello.WS_QNAME) @SOAPBinding(style = SOAPBinding.Style.RPC) public interface Hello extends Remote { public static final String WS_QNAME = "http://steeeven.org/client"; public String add(String a, String b) throws RemoteException; } package org.steeven.remote; import java.rmi.RemoteException; import java.rmi.registry.LocateRegistry; import java.rmi.registry.Registry; import java.rmi.server.UnicastRemoteObject; import javax.jws.WebService; import javax.jws.soap.SOAPBinding; import javax.xml.ws.Endpoint; @WebService(targetNamespace = Hello.WS_QNAME, portName = "Hello", serviceName = "Hello") @SOAPBinding(style = SOAPBinding.Style.RPC) public class ServerImpl extends UnicastRemoteObject implements Hello { private static final long serialVersionUID = 1L; protected ServerImpl() throws RemoteException { super(); } public String add(String a, String b) throws RemoteException { if ("steeven".equals(b)) throw new RuntimeException("SH IT"); return a + b; } public static void main(String[] args) throws Exception { // 发布为RMI服务 Registry registry = LocateRegistry.createRegistry(18888); registry.bind("server", new ServerImpl()); // 发布为web service Endpoint.publish("http://0.0.0.0:18889/server", new ServerImpl()); System.err.println("Server ready"); } }
实现和测试代码:
===========================================
package org.steeven.client; import java.lang.reflect.InvocationHandler; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.net.InetAddress; import java.net.InetSocketAddress; import java.net.NetworkInterface; import java.net.SocketException; import java.rmi.ConnectException; import java.util.LinkedList; public class HaClient<T> { private LinkedList<String> preferredUrls = new LinkedList<String>(); private LinkedList<String> otherUrls = new LinkedList<String>(); private T currentService; private Class<T> type; private ProtocolHandler protocalHandler; InvocationHandler invokeHandler = new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { try { try { System.out.println("invoke: " + method); return method.invoke(getServer(false), args); } catch (Throwable e) { if (protocalHandler .isServiceOut(e instanceof InvocationTargetException ? e .getCause() : e)) { System.out.println("Prefered server failed"); return method.invoke(getServer(true), args); } else throw e; } } catch (InvocationTargetException ex) { throw ex.getCause(); // InvocationTargetExcetpion.getCause() } } }; protected HaClient(ProtocolHandler protocalHandler, Class<T> type, String service, InetSocketAddress... nameServers) { this.protocalHandler = protocalHandler; this.type = type; for (InetSocketAddress address : nameServers) { if (isLocalHost(address.getAddress())) preferredUrls.add(protocalHandler.buildServiceUrl(service, address)); else otherUrls .add(protocalHandler.buildServiceUrl(service, address)); } } protected HaClient(ProtocolHandler protocalHandler, Class<T> type, LinkedList<String> preferredUrls, LinkedList<String> otherUrls) { this.type = type; this.protocalHandler = protocalHandler; this.preferredUrls = preferredUrls; this.otherUrls = otherUrls; } /** * check preferred server (local host) list first, then other server list. */ synchronized protected T getServer(boolean retry) throws Exception { // try local first, then others if (!retry && currentService != null) { System.out.println("user last server"); return currentService; } currentService = null; tryServers(preferredUrls); // try preferred if (currentService == null) tryServers(otherUrls); // try others if (currentService == null) throw new ConnectException("No server available now"); return currentService; } /** * remove active from list to current, roll failed server to bottom. */ @SuppressWarnings("unchecked") private void tryServers(LinkedList<String> list) throws Exception { LinkedList<String> badList = new LinkedList<String>(); try { String url; while (list.size() > 0) { url = list.peek(); try { System.out.println("trying: " + url); // TODO URI InetAddress.isReachable(n) to ping first currentService = (T) protocalHandler.lookupService(url, type); return; } catch (Exception e) { if (protocalHandler.isServiceOut(e)) { System.out.println("failed to try: " + url); list.pop(); badList.add(url); } else throw e; } } } finally { list.addAll(badList); } } @SuppressWarnings("unchecked") public T newInstance() { return (T) Proxy.newProxyInstance(type.getClassLoader(), new Class<?>[] { type }, invokeHandler); } private boolean isLocalHost(InetAddress address) { boolean local = address.isLoopbackAddress() || address.isAnyLocalAddress(); if (!local) try { local = (NetworkInterface.getByInetAddress(address) != null); } catch (SocketException e) { } return local; } public static <T> T create(ProtocolHandler protocol, Class<T> type, String service, InetSocketAddress... addresses) { return new HaClient<T>(protocol, type, service, addresses) .newInstance(); } public static <T> T create(ProtocolHandler protocol, Class<T> type, String service, int port, String... hosts) { InetSocketAddress[] addresses = new InetSocketAddress[hosts.length]; for (int i = 0; i < addresses.length; i++) { addresses[i] = new InetSocketAddress(hosts[i], port); if (addresses[i].getAddress() == null) throw new IllegalArgumentException("Invalid host: " + hosts[i]); } return new HaClient<T>(protocol, type, service, addresses) .newInstance(); } public abstract static class ProtocolHandler { public String buildServiceUrl(String service, InetSocketAddress address) { return getProtocol() + "://" + address.getAddress().getHostAddress() + ":" + address.getPort() + service; } public abstract String getProtocol(); public abstract boolean isServiceOut(Throwable e); public abstract Object lookupService(String url, Class<?> type) throws Exception; } } package org.steeven.client; import java.net.ConnectException; import java.net.URL; import javax.xml.namespace.QName; import javax.xml.ws.Service; import javax.xml.ws.WebServiceException; import org.steeven.remote.Hello; /** * High Available Http client. Provide service proxy that auto detect available * RMI service form several servers. * * @author xli * * @param <T> */ public class HttpProtocolHandler extends HaClient.ProtocolHandler { private String qname; public HttpProtocolHandler(String qname) { this.qname = qname; } @Override public String getProtocol() { return "http"; } public boolean isServiceOut(Throwable e) { return e instanceof WebServiceException && e.getCause() instanceof ConnectException; } @Override public Object lookupService(String url, Class<?> type) throws Exception { Service service = Service.create(new URL(url + "?wsdl"), new QName( qname, type.getSimpleName())); return service.getPort(new QName(Hello.WS_QNAME, type.getSimpleName()), type); } public static void main(String args[]) throws Exception { Hello hello = HaClient.create(new HttpProtocolHandler(Hello.WS_QNAME), Hello.class, "/server", 18889, "10.80.1.113", "10.80.2.184", "10.80.1.117"); while (true) { try { System.out.println("------------------------new-----------------"); System.out.println(hello.add("hello ", "steeven1")); } catch (Exception e) { e.printStackTrace(); } Thread.sleep(3000); } } } package org.steeven.client; import java.rmi.ConnectException; import java.rmi.Naming; import org.steeven.remote.Hello; /** * High Available RMI client. Provide service proxy that auto detect available * RMI service form several servers. * * @author xli * * @param <T> */ public class RmiProtocolHandler extends HaClient.ProtocolHandler { @Override public String getProtocol() { return "rmi"; } public boolean isServiceOut(Throwable e) { return e instanceof ConnectException; } @Override public Object lookupService(String url, Class<?> type) throws Exception { return Naming.lookup(url); } public static void main(String args[]) throws Exception { Hello hello = HaClient.create(new RmiProtocolHandler(), Hello.class, "/server", 18888, "10.80.1.113", "10.80.2.184", "10.80.1.117"); while (true) { try { System.out.println("------------------------new-----------------"); System.out.println(hello.add("hello ", "steeven1")); } catch (Exception e) { e.printStackTrace(); } Thread.sleep(3000); } } }
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