#vulnerable code 
                              @SuppressWarnings({"unchecked", "rawtypes"})
  @Override
  public void onServiceContextReceived(ServiceContext serviceContext) throws Throwable {
    FlowMessage flowMessage = serviceContext.getFlowMessage();
    if (serviceContext.isSync()) {
      CacheManager.get(serviceActorCachePrefix + serviceContext.getFlowName()).add(serviceContext.getId(), getSender(),
          defaultTimeToLive);
    }
    Serializer serializer = ExtensionLoader.load(Serializer.class).load(serviceContext.getCodec());

    Object result = null;
    Object param = null;
    try {
      ServiceContextUtil.fillServiceContext(serviceContext);
      String pType = getParamType(serviceContext);
      if (flowMessage.getMessage() != null && ClassUtil.exists(flowMessage.getMessageType())) {
        pType = flowMessage.getMessageType();
      }
      param = serializer.decode(flowMessage.getMessage(), pType);
      if (getFilter(serviceContext) != null) {
        getFilter(serviceContext).filter(param, serviceContext);
      }
      // logger.info("服务参数类型 {} : {}", pType, getService(serviceContext));
      result = ((Service) getService(serviceContext)).process(param, serviceContext);
    } catch (Throwable e) {
      handleException(serviceContext, e, param, serializer);
    }
    if (result != null && result instanceof CompletableFuture) {
      final Object tempParam = param;
      ((CompletableFuture<Object>) result).whenComplete((r, e) -> {
        if (e != null) {
          handleException(serviceContext, e, tempParam, serializer);
          return;
        }
        handleNextServices(serviceContext, r, flowMessage.getTransactionId(), serializer);
      });
    } else {
      handleNextServices(serviceContext, result, flowMessage.getTransactionId(), serializer);
    }
  } 
                            #location 19 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              @SuppressWarnings({"unchecked", "rawtypes"})
  @Override
  public void onServiceContextReceived(ServiceContext serviceContext) throws Throwable {
    FlowMessage flowMessage = serviceContext.getFlowMessage();
    if (serviceContext.isSync()) {
      CacheManager.get(serviceActorCachePrefix + serviceContext.getFlowName()).add(serviceContext.getId(), getSender(),
          defaultTimeToLive);
    }
    Serializer serializer = ExtensionLoader.load(Serializer.class).load(serviceContext.getCodec());

    Object result = null;
    Object param = null;
    try {
      ServiceContextUtil.fillServiceContext(serviceContext);
      param = getAndDecodeParam(serviceContext);
      if (getFilter(serviceContext) != null) {
        getFilter(serviceContext).filter(param, serviceContext);
      }
      // logger.info("服务参数类型 {} : {}", pType, getService(serviceContext));
      result = ((Service) getService(serviceContext)).process(param, serviceContext);
    } catch (Throwable e) {
      handleException(serviceContext, e, param, serializer);
    }
    if (result != null && result instanceof CompletableFuture) {
      final Object tempParam = param;
      ((CompletableFuture<Object>) result).whenComplete((r, e) -> {
        if (e != null) {
          handleException(serviceContext, e, tempParam, serializer);
          return;
        }
        handleNextServices(serviceContext, r, flowMessage.getTransactionId(), serializer);
      });
    } else {
      handleNextServices(serviceContext, result, flowMessage.getTransactionId(), serializer);
    }
  }