Dubbo 源码阅读（九）ProtocolFilterWrapper

Filter 调用

源码

public class ProtocolFilterWrapper implements Protocol {

    private final Protocol protocol;

    public ProtocolFilterWrapper(Protocol protocol) {
        if (protocol == null) {
            throw new IllegalArgumentException("protocol == null");
        }
        this.protocol = protocol;
    }

    private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
        Invoker<T> last = invoker;
        //得到所有的Filter
        List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
        if (!filters.isEmpty()) {
            for (int i = filters.size() - 1; i >= 0; i--) {
                final Filter filter = filters.get(i);
                final Invoker<T> next = last;
                last = new Invoker<T>() {

                    @Override
                    public Class<T> getInterface() {
                        return invoker.getInterface();
                    }

                    @Override
                    public URL getUrl() {
                        return invoker.getUrl();
                    }

                    @Override
                    public boolean isAvailable() {
                        return invoker.isAvailable();
                    }

                    @Override
                    public Result invoke(Invocation invocation) throws RpcException {
                    			//最后一个过滤器的invoke调用的是通过Protocol得到的Invoker
                    			//第一个过滤器的invoke调用的是第二个过滤器
                        return filter.invoke(next, invocation);
                    }

                    @Override
                    public void destroy() {
                        invoker.destroy();
                    }

                    @Override
                    public String toString() {
                        return invoker.toString();
                    }
                };
            }
        }
        //第一个Invoker的invoke调用第一个filter的invoke
        return last;
    }

    @Override
    public int getDefaultPort() {
        return protocol.getDefaultPort();
    }

    @Override
    public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
            return protocol.export(invoker);
        }
        return protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));
    }

    @Override
    public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
            return protocol.refer(type, url);
        }
        return buildInvokerChain(protocol.refer(type, url), Constants.REFERENCE_FILTER_KEY, Constants.CONSUMER);
    }

    @Override
    public void destroy() {
        protocol.destroy();
    }

}