motan源码分析四：客户端调用服务

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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:protocol default="true" name="motan" haStrategy="failover"
loadbalance="roundrobin" maxClientConnection="10" minClientConnection="2"/> 
<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"/> 
<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); }