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vertx 组合期货并在发生故障时结束响应。
一个请求想要执行以下步骤

  1. 从 mongodb 查询一个文档
  2. 检查它是否有字段名称。如果它有该字段，则以状态码 409 结束响应
  3. 如果没有字段名，则调用异步 api 来获取 JsonObject
  4. 从 JsonObject 获取一个字段并用它更新第一个文档中的字段名称
    private Future<JsonObject> findADocument(String id) {
        return mongoClient.findOne(COLLECTION, new JsonObject().put("id", id), null);
    }

    private Future<JsonObject> requestAnAsync(JsonObject jsonObject) {
        return Future.succeededFuture(new JsonObject());
    }

    private Future<JsonObject> check(Future<JsonObject> futureContent, String id) {
        return futureContent.map(jsonObject -> {
            String name = jsonObject.getString("name");
            if (name != null) {
                throw new DeployedException("Deployed already");
            }
            return jsonObject;
        });
    }

    private Future<MongoClientUpdateResult> update22(JsonObject jsonObject) {

        String name = jsonObject.getString("name");
        JsonObject query = new JsonObject()
                .put("id", "");
        JsonObject update = new JsonObject().put("$set", new JsonObject()
                .put("name", name));
        UpdateOptions options = new UpdateOptions().setMulti(false).setUpsert(false);
        return mongoClient.updateCollectionWithOptions(COLLECTION, query, update, options);
    }

    private void handleARequest(RoutingContext routingContext) {
        HttpServerResponse response = routingContext.response();

        String id = routingContext.request().getParam("id");

        Future<JsonObject> futureContent = findADocument(id);

        futureContent = check(futureContent, id);

        // hope to end response in the middle of the chain
        // but found these two onFailure handler would be executed
        futureContent.onFailure(err -> {
            if (err instanceof DeployedException) {
                DeployedException deployedException = (DeployedException) err;
                logger.error(deployedException.getMessage());
                sendError(409, deployedException.getMessage(), response);
            } else {
                err.printStackTrace();
                routingContext.response().setStatusCode(500).end("failed");
            }
        });

        Future<JsonObject> futureContent2 = futureContent.compose(this::requestAnAsync);

        Future<MongoClientUpdateResult> updateFuture = futureContent2.compose(this::update22);

        updateFuture.onSuccess(res -> {
            if (res.getDocModified() == 1) {
                System.out.println("updated !");
                routingContext.response().end();
            } else {
                System.out.println("Not Found !");
                routingContext.response().setStatusCode(404).end("Not Found");
            }
        }).onFailure(err -> {
            if (err instanceof DeployedException) {
                DeployedException deployedException = (DeployedException) err;
                logger.error(deployedException.getMessage());
                sendError(409, deployedException.getMessage(), response);
            } else {
                err.printStackTrace();
                routingContext.response().setStatusCode(500).end("failed");
            }
        });
    }

我希望在链的中间结束响应，但发现这两个 onFailure 处理程序将被执行。

（版本：Vert.X 4.1）

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