这一节我们来讲一下dubbo请求的泛化调用。

dubbo请求到网关后，会进入到ApacheDubboPlugin中，由于dubbo版本的不同，还有一个AlibabaDubboPlugin。我们先看ApachaDubboPlugin,他们逻辑基本相似。

请求来了后，会进入到Dubbo插件

//org.dromara.soul.plugin.apache.dubbo.ApacheDubboPlugin#doExecute
protected Mono<Void> doExecute(final ServerWebExchange exchange, final SoulPluginChain chain, final SelectorData selector, final RuleData rule) {
  //先获取dubbo的参数
  String body = exchange.getAttribute(Constants.DUBBO_PARAMS);
  SoulContext soulContext = exchange.getAttribute(Constants.CONTEXT);
  assert soulContext != null;
  //获取元数据
  MetaData metaData = exchange.getAttribute(Constants.META_DATA);
  //校验元数据的有效性
  if (!checkMetaData(metaData)) {
    assert metaData != null;
    log.error(" path is :{}, meta data have error.... {}", soulContext.getPath(), metaData.toString());
    exchange.getResponse().setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
    Object error = SoulResultWrap.error(SoulResultEnum.META_DATA_ERROR.getCode(), SoulResultEnum.META_DATA_ERROR.getMsg(), null);
    return WebFluxResultUtils.result(exchange, error);
  }
  //如果元数据的参数列表不为空但是我们的请求body为空，则返回异常
  if (StringUtils.isNoneBlank(metaData.getParameterTypes()) && StringUtils.isBlank(body)) {
    exchange.getResponse().setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
    Object error = SoulResultWrap.error(SoulResultEnum.DUBBO_HAVE_BODY_PARAM.getCode(), SoulResultEnum.DUBBO_HAVE_BODY_PARAM.getMsg(), null);
    return WebFluxResultUtils.result(exchange, error);
  }
  //进行dubbo的泛化调用并返回结果
  final Mono<Object> result = dubboProxyService.genericInvoker(body, metaData, exchange);
  return result.then(chain.execute(exchange));
}

我们来看一下泛化调用

//org.dromara.soul.plugin.apache.dubbo.proxy.ApacheDubboProxyService#genericInvoker
public Mono<Object> genericInvoker(final String body, final MetaData metaData, final ServerWebExchange exchange) throws SoulException {
  //从header中获取DubboTag信息
  String dubboTagRouteFromHttpHeaders = exchange.getRequest().getHeaders().getFirst(Constants.DUBBO_TAG_ROUTE);
  //如果DubboTag不为空，则放到RpcContext的附件中，用于dubbo传播中使用
  if (StringUtils.isNotBlank(dubboTagRouteFromHttpHeaders)) {
    RpcContext.getContext().setAttachment(CommonConstants.TAG_KEY, dubboTagRouteFromHttpHeaders);
  }
  //获取dubbo泛化配置
  ReferenceConfig<GenericService> reference = ApplicationConfigCache.getInstance().get(metaData.getPath());
  //如果获取为空，则通过initRef获取
  if (Objects.isNull(reference) || StringUtils.isEmpty(reference.getInterface())) {
    ApplicationConfigCache.getInstance().invalidate(metaData.getPath());
    reference = ApplicationConfigCache.getInstance().initRef(metaData);
  }
  //通过泛化配置获取到泛化Service
  GenericService genericService = reference.get();
  Pair<String[], Object[]> pair;
  if (ParamCheckUtils.dubboBodyIsEmpty(body)) {
    pair = new ImmutablePair<>(new String[]{}, new Object[]{});
  } else {
    pair = dubboParamResolveService.buildParameter(body, metaData.getParameterTypes());
  }
  //泛化异步调用
  CompletableFuture<Object> future = genericService.$invokeAsync(metaData.getMethodName(), pair.getLeft(), pair.getRight());
  //返回结果
  return Mono.fromFuture(future.thenApply(ret -> {
    if (Objects.isNull(ret)) {
      ret = Constants.DUBBO_RPC_RESULT_EMPTY;
    }
    exchange.getAttributes().put(Constants.DUBBO_RPC_RESULT, ret);
    exchange.getAttributes().put(Constants.CLIENT_RESPONSE_RESULT_TYPE, ResultEnum.SUCCESS.getName());
    return ret;
  })).onErrorMap(exception -> exception instanceof GenericException ? new SoulException(((GenericException) exception).getExceptionMessage()) : new SoulException(exception));
}

重点是如何获取到泛化配置的. 是通过ApplicationConfigCache.getInstance().initRef(metaData);获取到。

我们来看下ApplicationConfigCache

//org.dromara.soul.plugin.apache.dubbo.cache.ApplicationConfigCache
public final class ApplicationConfigCache {

    private ApplicationConfig applicationConfig;

    private RegistryConfig registryConfig;
}

他有两个dubbo的基本配置，应用配置和注册中心配置，这两个配置是为了构造泛化调用所必须的。他通过init方法注入到类中

//org.dromara.soul.plugin.apache.dubbo.cache.ApplicationConfigCache#init
public void init(final DubboRegisterConfig dubboRegisterConfig) {
  if (applicationConfig == null) {
    applicationConfig = new ApplicationConfig("soul_proxy");
  }
  if (registryConfig == null) {
    registryConfig = new RegistryConfig();
    registryConfig.setProtocol(dubboRegisterConfig.getProtocol());
    registryConfig.setId("soul_proxy");
    registryConfig.setRegister(false);
    //这里是我们从dubbo服务注册的dubbo插件里面的注册中心，从而能够保证我们soul网关代理的dubbo服务的注册中心和我们服务的注册中心使用同一个，从而能够保证服务调用通畅
    registryConfig.setAddress(dubboRegisterConfig.getRegister());
    Optional.ofNullable(dubboRegisterConfig.getGroup()).ifPresent(registryConfig::setGroup);
  }
}

init方法调用时机，就是之前我们讲的PluginDataHandler调用时机调用的。这里用到ApacheDubboPluginDataHandler

//org.dromara.soul.plugin.apache.dubbo.handler.ApacheDubboPluginDataHandler#handlerPlugin
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);
  }
}

我们看到，通过维护内存的DubboPlugin插件，从而更新dubbo的配置缓存，并刷新ApplicationConfigCache，dubbo配置缓存。

当我们第一次从缓存中获取ReferenceConfig的时候，肯定是空的，所以会走到initRef

//org.dromara.soul.plugin.apache.dubbo.cache.ApplicationConfigCache#initRef
public ReferenceConfig<GenericService> initRef(final MetaData metaData) {
  try {
    //从缓存获取，不为空直接返回
    ReferenceConfig<GenericService> referenceConfig = cache.get(metaData.getPath());
    if (StringUtils.isNoneBlank(referenceConfig.getInterface())) {
      return referenceConfig;
    }
  } catch (ExecutionException e) {
    log.error("init dubbo ref ex:{}", e.getMessage());
  }
  //build
  return build(metaData);
}

接下来看下build方法

//org.dromara.soul.plugin.apache.dubbo.cache.ApplicationConfigCache#build
public ReferenceConfig<GenericService> build(final MetaData metaData) {
  //手动构造ReferenceConfig
  ReferenceConfig<GenericService> reference = new ReferenceConfig<>();
  reference.setGeneric(true);
  //注入applicationConfig
  reference.setApplication(applicationConfig);
  //注入registryConfig
  reference.setRegistry(registryConfig);
  //注入serviceName
  reference.setInterface(metaData.getServiceName());
  reference.setProtocol("dubbo");
  //从metaData的rpcExt中获取额外的信息
  String rpcExt = metaData.getRpcExt();
  DubboParamExtInfo dubboParamExtInfo = GsonUtils.getInstance().fromJson(rpcExt, DubboParamExtInfo.class);
  if (Objects.nonNull(dubboParamExtInfo)) {
    //设置dubbo的version
    if (StringUtils.isNoneBlank(dubboParamExtInfo.getVersion())) {
      reference.setVersion(dubboParamExtInfo.getVersion());
    }
    //设置dubbo的group
    if (StringUtils.isNoneBlank(dubboParamExtInfo.getGroup())) {
      reference.setGroup(dubboParamExtInfo.getGroup());
    }
    //设置负载均衡策略
    if (StringUtils.isNoneBlank(dubboParamExtInfo.getLoadbalance())) {
      final String loadBalance = dubboParamExtInfo.getLoadbalance();
      reference.setLoadbalance(buildLoadBalanceName(loadBalance));
    }
    //设置url
    if (StringUtils.isNoneBlank(dubboParamExtInfo.getUrl())) {
      reference.setUrl(dubboParamExtInfo.getUrl());
    }
    Optional.ofNullable(dubboParamExtInfo.getTimeout()).ifPresent(reference::setTimeout);
    Optional.ofNullable(dubboParamExtInfo.getRetries()).ifPresent(reference::setRetries);
  }
  try {
    //通过get获取代理的对象，如果能够获取到，put到cache中
    Object obj = reference.get();
    if (obj != null) {
      log.info("init apache dubbo reference success there meteData is :{}", metaData.toString());
      cache.put(metaData.getPath(), reference);
    }
  } catch (Exception e) {
    log.error("init apache dubbo reference ex:{}", e.getMessage());
  }
  return reference;
}

至此，网关如何实现的dubbo调用就讲完了，主要依赖的就是dubbo自己的泛化调用，并通过内存维护dubbo的相关配置，从而构造泛化配置，获取provider代理，并直接调用