motan源码分析四：客户端调用服务
在第一章中，我们分析了服务的发布与注册，本章中将简单的分析一下客户端调用服务的代码及流程，本文将以spring加载的方式进行分析。
1.在DemoRpcClient类的main()方法中加载类：
ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{"classpath:motan_demo_client.xml"});
MotanDemoService service = (MotanDemoService) ctx.getBean("motanDemoReferer");
2.上面加载了spring的配置文件motan_demo_client.xml
<motan:registry regProtocol="zookeeper" name="registry" address="127.0.0.1:2181" connectTimeout="2000"/>
<!-- motan协议配置 -->
<motan:protocol default="true" name="motan" haStrategy="failover"
loadbalance="roundrobin" maxClientConnection="10" minClientConnection="2"/>
<!-- 通用referer基础配置 -->
<motan:basicReferer requestTimeout="200" accessLog="false"
retries="2" group="motan-demo-rpc" module="motan-demo-rpc"
application="myMotanDemo" protocol="motan" registry="registry"
id="motantestClientBasicConfig" throwException="false" check="true"/>
<!-- 具体referer配置。使用方通过beanid使用服务接口类 -->
<motan:referer id="motanDemoReferer"
interface="com.weibo.motan.demo.service.MotanDemoService"
connectTimeout="300" requestTimeout="300" basicReferer="motantestClientBasicConfig"/>
经过spring装载RefererConfig后，每次向spring框架getBean时会调用RefererConfig的getRef()方法
3.获取接口MotanDemoService的实现类代码如下：
public Object getRef() { if(ref == null) initRef();//初始化 return ref; } public synchronized void initRef() { if(initialized.get()) return; try { interfaceClass = Class.forName(interfaceClass.getName(), true, Thread.currentThread().getContextClassLoader()); } catch(ClassNotFoundException e) { throw new MotanFrameworkException((new StringBuilder("ReferereConfig initRef Error: Class not found ")).append(interfaceClass.getName()).toString(), e, MotanErrorMsgConstant.FRAMEWORK_INIT_ERROR); } if(CollectionUtil.isEmpty(protocols))//protocol配置是否为空 throw new MotanFrameworkException(String.format("%s RefererConfig is malformed, for protocol not set correctly!", new Object[] { interfaceClass.getName() })); checkInterfaceAndMethods(interfaceClass, methods); clusterSupports = new ArrayList(protocols.size());//初始化集群支持类列表，可以支持多个 List clusters = new ArrayList(protocols.size());//初始化集群类列表，可以支持多个 String proxy = null; ConfigHandler configHandler = (ConfigHandler)ExtensionLoader.getExtensionLoader(com/weibo/api/motan/config/handler/ConfigHandler).getExtension("default");//加载SimpleConfigHandler List registryUrls = loadRegistryUrls();//加载注册中心url列表，可以支持多个注册中心 String localIp = getLocalHostAddress(registryUrls); for(Iterator iterator = protocols.iterator(); iterator.hasNext();) { ProtocolConfig protocol = (ProtocolConfig)iterator.next(); LoggerUtil.info((new StringBuilder("ProtocolConfig's")).append(protocol.getName()).toString()); Map params = new HashMap(); params.put(URLParamType.nodeType.getName(), "referer"); params.put(URLParamType.version.getName(), URLParamType.version.getValue()); params.put(URLParamType.refreshTimestamp.getName(), String.valueOf(System.currentTimeMillis())); collectConfigParams(params, new AbstractConfig[] { protocol, basicReferer, extConfig, this }); collectMethodConfigParams(params, getMethods()); URL refUrl = new URL(protocol.getName(), localIp, 0, interfaceClass.getName(), params); ClusterSupport clusterSupport = createClusterSupport(refUrl, configHandler, registryUrls); clusterSupports.add(clusterSupport); clusters.add(clusterSupport.getCluster()); proxy = proxy != null ? proxy : refUrl.getParameter(URLParamType.proxy.getName(), URLParamType.proxy.getValue()); } ref = configHandler.refer(interfaceClass, clusters, proxy);//调用SimpleConfigHandler的refer方法获取接口实现类 initialized.set(true); }
4.下面我们来看一下SimpleConfigHandler的refer方法的代理实现，使用了jdk的动态代理技术
public <T> T refer(Class<T> interfaceClass, List<Cluster<T>> clusters, String proxyType) {
ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getExtension(proxyType);//创建代理工厂
return proxyFactory.getProxy(interfaceClass, new RefererInvocationHandler<T>(interfaceClass, clusters));//获取代理类
}
public class JdkProxyFactory implements ProxyFactory {
@SuppressWarnings("unchecked")
public <T> T getProxy(Class<T> clz, InvocationHandler invocationHandler) {
return (T) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[] {clz}, invocationHandler);//使用jdk的动态代理，实际调用的代码是下面的的invoke方法
}
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
DefaultRequest request = new DefaultRequest();//封装通信用的request，request和response是在客户端和服务端通信的两个对象
request.setRequestId(RequestIdGenerator.getRequestId());
request.setArguments(args);
request.setMethodName(method.getName());
request.setParamtersDesc(ReflectUtil.getMethodParamDesc(method));
request.setInterfaceName(clz.getName());
request.setAttachment(URLParamType.requestIdFromClient.getName(), String.valueOf(RequestIdGenerator.getRequestIdFromClient()));
// 当 referer配置多个protocol的时候，比如A,B,C，
// 那么正常情况下只会使用A，如果A被开关降级，那么就会使用B，B也被降级，那么会使用C
for (Cluster<T> cluster : clusters) {//motan支持多个protocol的配置，也就是支持多个cluster，但是默认情况下只取第一个，如果前面的被降级，则取下一个
String protocolSwitcher = MotanConstants.PROTOCOL_SWITCHER_PREFIX + cluster.getUrl().getProtocol();
Switcher switcher = switcherService.getSwitcher(protocolSwitcher);
if (switcher != null && !switcher.isOn()) {
continue;
}
List<Referer<T>> referL = cluster.getReferers();//此段代码为我单独添加的，目的是证明客户端在配置多个注册中心的情况下，cluster可以支持跨注册中心的调用
for(Referer<T> refer : referL){
LoggerUtil.info(refer.getServiceUrl().getUri()+refer.getServiceUrl().getPath());
}
request.setAttachment(URLParamType.version.getName(), cluster.getUrl().getVersion());
request.setAttachment(URLParamType.clientGroup.getName(), cluster.getUrl().getGroup());
// 带上client的application和module
request.setAttachment(URLParamType.application.getName(), ApplicationInfo.getApplication(cluster.getUrl()).getApplication());
request.setAttachment(URLParamType.module.getName(), ApplicationInfo.getApplication(cluster.getUrl()).getModule());
Response response = null;
boolean throwException =
Boolean.parseBoolean(cluster.getUrl().getParameter(URLParamType.throwException.getName(),
URLParamType.throwException.getValue()));
try {
response = cluster.call(request);//调用cluster的call方法
return response.getValue();//获取返回信息
} catch (RuntimeException e) {
if (ExceptionUtil.isBizException(e)) {
Throwable t = e.getCause();
// 只抛出Exception，防止抛出远程的Error
if (t != null && t instanceof Exception) {
throw t;
} else {
String msg =
t == null ? "biz exception cause is null" : ("biz exception cause is throwable error:" + t.getClass()
+ ", errmsg:" + t.getMessage());
throw new MotanServiceException(msg, MotanErrorMsgConstant.SERVICE_DEFAULT_ERROR);
}
} else if (!throwException) {
LoggerUtil.warn("RefererInvocationHandler invoke false, so return default value: uri=" + cluster.getUrl().getUri()
+ " " + MotanFrameworkUtil.toString(request), e);
return getDefaultReturnValue(method.getReturnType());
} else {
LoggerUtil.error(
"RefererInvocationHandler invoke Error: uri=" + cluster.getUrl().getUri() + " "
+ MotanFrameworkUtil.toString(request), e);
throw e;
}
}
}
throw new MotanServiceException("Referer call Error: cluster not exist, interface=" + clz.getName() + " "
+ MotanFrameworkUtil.toString(request), MotanErrorMsgConstant.SERVICE_UNFOUND);
}
本章知识点总结：
1.客户端在获取业务接口的实现类时，使用了jdk的动态代理技术；
2.客户端可以支持多个注册中心；
3.客户端可以支持多个cluster，但是只取最前面有效那个；
4.使用request和response对象进行信息的传递。
