让我们先来定义一下我们可能在网络应用中使用的不同 API 方法。如图 9-1 所示，我们将重点关注最常用和最著名的模式。
但这并不意味着微前端只能使用这些实现。例如，您可以为 WebSocket（通过单个 TCP 连接的双向计算机通信协议）或超媒体选择合适的方法。在超媒体的情况下--例如，在响应内容中使用带有超媒体链接的 REST--消费 API 的客户端可以通过遍历这些链接动态导航到相应的资源。关键是要学会如何使用 BFF、API 网关或服务字典模式。
图 9-1. 微前端和 API 层
本章我们将分析三种模式：
服务字典
服务字典只是供客户端使用的服务列表。它主要是在我们用单体或模块化单体架构开发 API 层时使用；不过，它也可以用带 API 网关的微服务架构等其他架构来实现。服务字典避免了在持续集成（CI）过程中创建共享库、定义环境变量或注入配置的需要，也消除了对前端代码库中所有端点进行硬编码的要求。当微前端加载时，字典会首次加载，允许客户端直接从服务字典中检索要使用的 URL。
BFF 是 API 网关模式的扩展，为每种客户类型创建了一个单一入口。例如，我们可以为网络应用程序建立一个 BFF，为移动设备建立另一个 BFF，为我们正在商业化的物联网（IoT）设备建立第三个 BFF。BFF 减少了客户端和服务器之间的对话，聚合 API 响应并返回一个简单的数据结构，供客户端解析并在用户界面内呈现。这样就能在很大程度上自由塑造专用于客户端的 API，并减少客户端与后端层之间的往返次数。
这些模式也不是相互排斥的，它们可以组合在一起工作。
值得一提的另一种可能性是为客户端编写 API 端点库。不过，我不鼓励在微前端中采用这种做法，因为我们有可能在某些微前端中嵌入较旧版本的库，因此，用户界面可能会出现一些问题，比如信息过时，甚至由于某些 ...
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