Apache Shenyu源码阅读计划（三）Dubbo请求

@Override
protected Mono<Void> doExecute(final ServerWebExchange exchange, final ShenyuPluginChain chain, final SelectorData selector, final RuleData rule) {
    // 获取请求体
    String param = exchange.getAttribute(Constants.PARAM_TRANSFORM);
    // 获取shenyu上下文，里面包括了rpc类型、http请求方法、路径、rpc方法所在的类等信息，具体可以看下面的图
    ShenyuContext shenyuContext = exchange.getAttribute(Constants.CONTEXT);
    assert shenyuContext != null;
    // 获取元数据，这个应该跟admin里面配置的元数据是一个东西
    MetaData metaData = exchange.getAttribute(Constants.META_DATA);
    // 如果metaData有问题就进去（为空/服务方法为空/服务类不存在），然后直接报个错。
    if (!checkMetaData(metaData)) {
        ...
    }
    // 如果请求体有问题，也是直接报个错。
    if (StringUtils.isNoneBlank(metaData.getParameterTypes()) && StringUtils.isBlank(param)) {
        ...
    }
    // ！这里应该就是去调用dubbo的服务了，等下仔细看。
    Object result = alibabaDubboProxyService.genericInvoker(param, metaData);
    // 整理一下调用的结果
    if (Objects.nonNull(result)) {
        exchange.getAttributes().put(Constants.RPC_RESULT, result);
    } else {
        exchange.getAttributes().put(Constants.RPC_RESULT, Constants.DUBBO_RPC_RESULT_EMPTY);
    }
    exchange.getAttributes().put(Constants.CLIENT_RESPONSE_RESULT_TYPE, ResultEnum.SUCCESS.getName());
    return chain.execute(exchange);
}

public Object genericInvoker(final String body, final MetaData metaData) throws ShenyuException {
    // 1. 从缓存中拿到对应的dubbo服务的ReferenceConfig
    ReferenceConfig<GenericService> reference = ApplicationConfigCache.getInstance().get(metaData.getPath());
    // 如果拿到的reference是空的，或者里面没有具体服务的方法就进去
    if (Objects.isNull(reference) || StringUtils.isEmpty(reference.getInterface())) {
        ApplicationConfigCache.getInstance().invalidate(metaData.getPath());
        // 重新按照元数据构建出reference
        reference = ApplicationConfigCache.getInstance().initRef(metaData);
    }
    // 根据reference拿到具体服务的句柄，这是dubbo的内容
    GenericService genericService = reference.get();
    try {
        Pair<String[], Object[]> pair;
        if (StringUtils.isBlank(metaData.getParameterTypes()) || ParamCheckUtils.dubboBodyIsEmpty(body)) {
            pair = new ImmutablePair<>(new String[]{}, new Object[]{});
        } else {
            // 2. 如果有请求体，那就构建出pair
            pair = bodyParamResolveService.buildParameter(body, metaData.getParameterTypes());
        }
        // 传入参数，调用远程服务，并返回
        return genericService.$invoke(metaData.getMethodName(), pair.getLeft(), pair.getRight());
    } catch (GenericException e) {
        log.error("dubbo invoker have exception", e);
        throw new ShenyuException(e.getExceptionMessage());
    }
}

public class AlibabaDubboPluginDataHandler implements PluginDataHandler {

    @Override
    public void handlerPlugin(final PluginData pluginData) {
        if (null != pluginData && pluginData.getEnabled()) {
            DubboRegisterConfig dubboRegisterConfig = GsonUtils.getInstance().fromJson(pluginData.getConfig(), DubboRegisterConfig.class);
            DubboRegisterConfig exist = Singleton.INST.get(DubboRegisterConfig.class);
            if (Objects.isNull(dubboRegisterConfig)) {
                return;
            }
            if (Objects.isNull(exist) || !dubboRegisterConfig.equals(exist)) {
                // If it is null, initialize it
                ApplicationConfigCache.getInstance().init(dubboRegisterConfig);
                ApplicationConfigCache.getInstance().invalidateAll();
            }
            Singleton.INST.single(DubboRegisterConfig.class, dubboRegisterConfig);
        }
    }

    @Override
    public String pluginNamed() {
        return PluginEnum.DUBBO.getName();
    }
}

public class AlibabaDubboMetaDataSubscriber implements MetaDataSubscriber {

    private static final ConcurrentMap<String, MetaData> META_DATA = Maps.newConcurrentMap();

    @Override
    public void onSubscribe(final MetaData metaData) {
        if (RpcTypeEnum.DUBBO.getName().equals(metaData.getRpcType())) {
            MetaData exist = META_DATA.get(metaData.getPath());
            if (Objects.isNull(exist) || Objects.isNull(ApplicationConfigCache.getInstance().get(metaData.getPath()))) {
                // The first initialization
                ApplicationConfigCache.getInstance().initRef(metaData);
            } else {
                // There are updates, which only support the update of four properties of serviceName rpcExt parameterTypes methodName,
                // because these four properties will affect the call of Dubbo;
                if (!Objects.equals(metaData.getServiceName(), exist.getServiceName())
                        || !Objects.equals(metaData.getRpcExt(), exist.getRpcExt())
                        || !Objects.equals(metaData.getParameterTypes(), exist.getParameterTypes())
                        || !Objects.equals(metaData.getMethodName(), exist.getMethodName())) {
                    ApplicationConfigCache.getInstance().build(metaData);
                }
            }
            META_DATA.put(metaData.getPath(), metaData);
        }
    }

    @Override
    public void unSubscribe(final MetaData metaData) {
        if (RpcTypeEnum.DUBBO.getName().equals(metaData.getRpcType())) {
            ApplicationConfigCache.getInstance().invalidate(metaData.getPath());
            META_DATA.remove(metaData.getPath());
        }
    }
}