Dubbo之ReferenceBean将远程接口的实现实例化到本地的过程

一直很奇怪为什么引用dubbo的service时并没有用@Reference就可以引用到，原来是ReferenceBean的功劳

源码如下：

@Bean
public ReferenceBean repaymentPlanServiceReferenceBean(){
    ReferenceBean referenceBean = new ReferenceBean<>();
    referenceBean.setInterface(PLRepaymentPlanService.class);
    referenceBean.setCheck(false);
    referenceBean.setValidation("true");
    return referenceBean;
}

 

ReferenceBean实现了InitializingBean的afterPropertiesSet方法，在类构造完成后会自动调用这个方法

public void afterPropertiesSet() throws Exception {
...
if (b != null && b.booleanValue()) {
    getObject();
}
}

public Object getObject() throws Exception {
    return get();
}

然后 我们进入了ReferenceConfig中的get()方法

public synchronized T get() {
    if (destroyed) {
        throw new IllegalStateException("Already destroyed!");
    }
    if (ref == null) {
       //核心逻辑 一系列初始化操作 并且包括了将接口实现实例化到本地
        init();
    }
    return ref;
}

private void init() {
//...

ref = createProxy(map);
}

//这段代码重点就是最后一行
private T createProxy(Map map) {
    URL tmpUrl = new URL("temp", "localhost", 0, map);
    final boolean isJvmRefer;
    if (isInjvm() == null) {
        if (url != null && url.length() > 0) { //指定URL的情况下，不做本地引用
            isJvmRefer = false;
        } else if (InjvmProtocol.getInjvmProtocol().isInjvmRefer(tmpUrl)) {
            //默认情况下如果本地有服务暴露，则引用本地服务.
            isJvmRefer = true;
        } else {
            isJvmRefer = false;
        }
    } else {
        isJvmRefer = isInjvm().booleanValue();
    }

    if (isJvmRefer) {
        URL url = new URL(Constants.LOCAL_PROTOCOL, NetUtils.LOCALHOST, 0, interfaceClass.getName()).addParameters(map);
        invoker = refprotocol.refer(interfaceClass, url);
        if (logger.isInfoEnabled()) {
            logger.info("Using injvm service " + interfaceClass.getName());
        }
    } else {
        if (url != null && url.length() > 0) { // 用户指定URL，指定的URL可能是对点对直连地址，也可能是注册中心URL
            String[] us = Constants.SEMICOLON_SPLIT_PATTERN.split(url);
            if (us != null && us.length > 0) {
                for (String u : us) {
                    URL url = URL.valueOf(u);
                    if (url.getPath() == null || url.getPath().length() == 0) {
                        url = url.setPath(interfaceName);
                    }
                    if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
                        urls.add(url.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));
                    } else {
                        urls.add(ClusterUtils.mergeUrl(url, map));
                    }
                }
            }
        } else { // 通过注册中心配置拼装URL
            List us = loadRegistries(false);
            if (us != null && us.size() > 0) {
                for (URL u : us) {
                    URL monitorUrl = loadMonitor(u);
                    if (monitorUrl != null) {
                        map.put(Constants.MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
                    }
                    urls.add(u.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));
                }
            }
            if (urls == null || urls.size() == 0) {
                throw new IllegalStateException("No such any registry to reference " + interfaceName + " on the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", please config  to your spring config.");
            }
        }

        if (urls.size() == 1) {
            invoker = refprotocol.refer(interfaceClass, urls.get(0));
        } else {
            List> invokers = new ArrayList>();
            URL registryURL = null;
            for (URL url : urls) {
                invokers.add(refprotocol.refer(interfaceClass, url));
                if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
                    registryURL = url; // 用了最后一个registry url
                }
            }
            if (registryURL != null) { // 有 注册中心协议的URL
                // 对有注册中心的Cluster 只用 AvailableCluster
                URL u = registryURL.addParameter(Constants.CLUSTER_KEY, AvailableCluster.NAME);
                invoker = cluster.join(new StaticDirectory(u, invokers));
            } else { // 不是 注册中心的URL
                invoker = cluster.join(new StaticDirectory(invokers));
            }
        }
    }

    Boolean c = check;
    if (c == null && consumer != null) {
        c = consumer.isCheck();
    }
    if (c == null) {
        c = true; // default true
    }
    if (c && !invoker.isAvailable()) {
        throw new IllegalStateException("Failed to check the status of the service " + interfaceName + ". No provider available for the service " + (group == null ? "" : group + "/") + interfaceName + (version == null ? "" : ":" + version) + " from the url " + invoker.getUrl() + " to the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion());
    }
    if (logger.isInfoEnabled()) {
        logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
    }
    // 创建服务代理
    return (T) proxyFactory.getProxy(invoker);
}

调用了StubProxyFactoryWrapper  implements ProxyFactory 的getProxy

public  T getProxy(Invoker invoker) throws RpcException {
    T proxy = proxyFactory.getProxy(invoker);
    //...
    return proxy;
}

继而调用了AbstractProxyFactory implements ProxyFactory的getProxy

public  T getProxy(Invoker invoker) throws RpcException {
    Class[] interfaces = null;
    String config = invoker.getUrl().getParameter("interfaces");
    if (config != null && config.length() > 0) {
        String[] types = Constants.COMMA_SPLIT_PATTERN.split(config);
        if (types != null && types.length > 0) {
            interfaces = new Class[types.length + 2];
            interfaces[0] = invoker.getInterface();
            interfaces[1] = EchoService.class;
            for (int i = 0; i < types.length; i++) {
                interfaces[i + 1] = ReflectUtils.forName(types[i]);
            }
        }
    }
    if (interfaces == null) {
        interfaces = new Class[]{invoker.getInterface(), EchoService.class};
    }
    return getProxy(invoker, interfaces);
}

最终调用了

public class JavassistProxyFactory extends AbstractProxyFactory {

    @SuppressWarnings("unchecked")
    public  T getProxy(Invoker invoker, Class[] interfaces) {
        //创建了实现类的实例
        return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker));
    }

    public  Invoker getInvoker(T proxy, Class type, URL url) {
        // TODO Wrapper类不能正确处理带$的类名
        final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
        return new AbstractProxyInvoker(proxy, type, url) {
            @Override
            protected Object doInvoke(T proxy, String methodName,
                                      Class[] parameterTypes,
                                      Object[] arguments) throws Throwable {
                return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
            }
        };
    }

}