模块概念的引入，是本框架的一大优势，而跨JVM的远程服务调用则是另一个最有价值的功能。
《本地服务调用》一文中我们讲解了跨模块间的服务调用可以是这样的：
ServiceHelper.invoke("pas","AuthService:auth",new Data("principal",principalInstance,"url","http://localhost:8080/pas/index.shtml"));
如果这个pas不是本地模块，而是远程模块，又该如何调用呢？
正如你期望的那样，还是上面这样调用，这意味着，无论这个pas模块部署在什么地方，你得代码复杂度没有变化。可怜了那些靠代码量体现工作量的程序猿们，处理了一个如此复杂的工作，还是这么简单的两行代码。
远程服务的实现方法
flying中是通过hessian来实现远程调用的，主要是因为hessian简单、功能够用。
服务提供端代码：
1、定义Hessian服务提供接口
public interface RemoteService {
RemoteValue invoke(Principal principal, String moduleId, String serviceId, RemoteValue request) throws Exception;
}
2、定义Hessian的Servlet
@WebServlet(value="/remoting")
public class HessianRemoteService extends HessianServlet implements RemoteService{
private final static Logger logger = Logger.getLogger(HessianRemoteService.class);
public void init(ServletConfig servletConfig) throws ServletException {
super.init(servletConfig);
}
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)servletRequest;
long start = System.currentTimeMillis();
final String requestURI = req.getRequestURI() + (req.getQueryString() == null?"":"?" + req.getQueryString());
try {
super.service(servletRequest, servletResponse);
} finally {
logger.info("Access(" + (System.currentTimeMillis() - start) + ")\tURI:" + requestURI);
}
}
public RemoteValue invoke(Principal principal, String moduleId, String serviceId, RemoteValue remoteData) throws Exception {
long start = System.currentTimeMillis();
try {
Data req = remoteData.getValue();
LocalModule module = Application.getInstance().getModules().getLocalModule(moduleId);
ThreadContext.getContext().reset(module, serviceId, req, principal);
ThreadContext.getContext().setInvokeType(ThreadContext.InvokeType.Remote);
Data result = module.invoke(serviceId, req);
remoteData.setValue(result);
} catch (Exception e){
remoteData.setException(e);
} finally {
logger.info("RemoteInvoker(" + (System.currentTimeMillis() - start) + ")\tModuleId:" + moduleId+";ServiceId:" + serviceId);
}
return remoteData;
}
}
3、实现Hessian调用的客户端
public class HessianRemoteServiceInvoker implements RemoteServiceInvoker {
@Override
public Data invoke(Principal principal, LocalModule localModule, String remoteModuleId, String serviceId, Data request)
throws Exception {
if (localModule == null) {
localModule = ThreadContext.getContext().getModule();
}
if (localModule != null) {
Thread.currentThread().setContextClassLoader(localModule.getClassLoader());
}
String url = Application.getInstance().getModules().getRemoteModule(remoteModuleId).getPath();
RemoteService remoteService = getRemoteService(url);
Map<String, Object> nonSerializable = request.filterValues(new DataFilter(){
@Override
public boolean isValid(String key, Object value) {
return key != null && value != null && (value instanceof Serializable);
}
});
final RemoteValue res = remoteService.invoke(principal, remoteModuleId, serviceId, new RemoteValue(request));
if (res.getException() != null) {
throw (Exception) res.getException();
} else {
return res.getValue().putAll(nonSerializable);
}
}
private static Map<String,RemoteService> remoteServiceMap = new ConcurrentHashMap<String, RemoteService>();
private static Object lock = new Object();
private RemoteService getRemoteService(String url) throws Exception {
RemoteService remoteService = remoteServiceMap.get(url);
if(remoteService==null){
synchronized (lock) {
remoteService = remoteServiceMap.get(url);
if(remoteService==null){
HessianProxyFactory factory = new HessianProxyFactory(Thread.currentThread().getContextClassLoader());
HttpClientHessianConnectionFactory hessianConnectionFactory = HttpClientHessianConnectionFactory.getInstance();
//hessianConnectionFactory.addHeader("authorization", "admin");
factory.setConnectionFactory(hessianConnectionFactory);
final Data config = Application.getInstance().getConfigs("hessian");
if (config != null) {
factory.setConnectTimeout(config.getLong("connectTimeout", 10000l));
factory.setReadTimeout(config.getLong("readTimeout", 10000l));
factory.setHessian2Reply(config.getBoolean("hessian2Reply", true));
factory.setHessian2Request(config.getBoolean("hesian2Request", false));
factory.setChunkedPost(config.getBoolean("chunkedPost", true));
factory.setDebug(config.getBoolean("debug", false));
}
remoteService = (RemoteService) factory.create(RemoteService.class, url);
remoteServiceMap.put(url, remoteService);
}
}
}
return remoteService;
}
}
4、实现RemoteModule中的invoke方法：
public Data invoke(String serviceId, Data request) throws Exception {
return RemoteServiceInvokerHelper.invoke(remoteServiceInvoker, id, serviceId, request);
}
框架源码：https://github.com/hifong/flying
博客空间：http://www.cnblogs.com/hifong/
Demo应用：https://github.com/hifong/pas
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