170 lines
5.3 KiB
Markdown
170 lines
5.3 KiB
Markdown
<h1 align="center">Fastify</h1>
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<a id="encapsulation"></a>
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## 封装
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“封装上下文”是 Fastify 的一个基础特性，负责控制[路由](./Routes.md)能访问的[装饰器](./Decorators.md)、[钩子](./Hooks.md)以及[插件](./Plugins.md)。下图是封装上下文的抽象表现：
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上图可归纳为以下几块内容：
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1. _顶层上下文 (root context)_
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2. 三个 _顶层插件 (root plugin)_
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3. 两个 _子上下文 (child context)_，每个 _子上下文_ 拥有
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- 两个 _子插件 (child plugin)_
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- 一个 _孙子上下文 (grandchild context)_，其又拥有
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- 三个 _子插件 (child plugin)_
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任意 _子上下文_ 或 _孙子上下文_ 都有权访问 _顶层插件_。_孙子上下文_ 有权访问它上级的 _子上下文_ 中注册的 _子插件_，但 _子上下文_ _无权_ 访问它下级的 _孙子上下文中_ 注册的 _子插件_。
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在 Fastify 中，除了 _顶层上下文_，一切皆为[插件](./Plugins.md)。下文的例子也不例外，所有的“上下文”和“插件”都是包含装饰器、钩子、插件及路由的插件。该例子为有三个路由的 REST API 服务器，第一个路由 (`/one`) 需要鉴权 (使用 [fastify-bearer-auth][bearer])，第二个路由 (`/two`) 无需鉴权，第三个路由 (`/three`) 有权访问第二个路由的上下文：
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```js
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"use strict";
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const fastify = require("fastify")();
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fastify.decorateRequest("answer", 42);
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fastify.register(async function authenticatedContext(childServer) {
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childServer.register(require("fastify-bearer-auth"), { keys: ["abc123"] });
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childServer.route({
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path: "/one",
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method: "GET",
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handler(request, response) {
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response.send({
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answer: request.answer,
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// request.foo 会是 undefined，因为该值是在 publicContext 中定义的
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foo: request.foo,
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// request.bar 会是 undefined，因为该值是在 grandchildContext 中定义的
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bar: request.bar,
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});
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},
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});
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});
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fastify.register(async function publicContext(childServer) {
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childServer.decorateRequest("foo", "foo");
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childServer.route({
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path: "/two",
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method: "GET",
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handler(request, response) {
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response.send({
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answer: request.answer,
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foo: request.foo,
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// request.bar 会是 undefined，因为该值是在 grandchildContext 中定义的
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bar: request.bar,
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});
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},
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});
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childServer.register(async function grandchildContext(grandchildServer) {
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grandchildServer.decorateRequest("bar", "bar");
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grandchildServer.route({
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path: "/three",
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method: "GET",
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handler(request, response) {
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response.send({
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answer: request.answer,
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foo: request.foo,
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bar: request.bar,
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});
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},
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});
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});
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});
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fastify.listen(8000);
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```
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上面的例子展示了所有封装相关的概念：
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1. 每个 _子上下文_ (`authenticatedContext`、`publicContext` 及 `grandchildContext`) 都有权访问在 _顶层上下文_ 中定义的 `answer` 请求装饰器。
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2. 只有 `authenticatedContext` 能访问 `fastify-bearer-auth` 插件。
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3. `publicContext` 和 `grandchildContext` 都能访问 `foo` 请求装饰器。
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4. 只有 `grandchildContext` 能访问 `bar` 请求装饰器。
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启动服务来验证这些概念吧：
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```sh
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# curl -H 'authorization: Bearer abc123' http://127.0.0.1:8000/one
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{"answer":42}
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# curl http://127.0.0.1:8000/two
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{"answer":42,"foo":"foo"}
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# curl http://127.0.0.1:8000/three
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{"answer":42,"foo":"foo","bar":"bar"}
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```
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[bearer]: https://github.com/fastify/fastify-bearer-auth
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<a id="shared-context"></a>
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## 在上下文间共享
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请注意，在上文例子中，每个上下文都 _仅_ 从父级上下文进行继承，而父级上下文无权访问后代上下文中定义的实体。在某些情况下，我们并不想要这一默认行为。使用 [fastify-plugin][fastify-plugin] ，便能允许父级上下文访问到后代上下文中定义的实体。
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假设上例的 `publicContext` 需要获取 `grandchildContext` 中定义的 `bar` 装饰器，我们可以重写代码如下：
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```js
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"use strict";
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const fastify = require("fastify")();
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const fastifyPlugin = require("fastify-plugin");
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fastify.decorateRequest("answer", 42);
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// 为了代码清晰，这里省略了 `authenticatedContext`
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fastify.register(async function publicContext(childServer) {
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childServer.decorateRequest("foo", "foo");
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childServer.route({
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path: "/two",
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method: "GET",
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handler(request, response) {
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response.send({
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answer: request.answer,
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foo: request.foo,
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bar: request.bar,
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});
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},
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});
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childServer.register(fastifyPlugin(grandchildContext));
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async function grandchildContext(grandchildServer) {
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grandchildServer.decorateRequest("bar", "bar");
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grandchildServer.route({
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path: "/three",
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method: "GET",
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handler(request, response) {
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response.send({
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answer: request.answer,
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foo: request.foo,
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bar: request.bar,
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});
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},
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});
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}
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});
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fastify.listen(8000);
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```
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重启服务，访问 `/two` 和 `/three` 路由：
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```sh
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# curl http://127.0.0.1:8000/two
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{"answer":42,"foo":"foo","bar":"bar"}
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# curl http://127.0.0.1:8000/three
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{"answer":42,"foo":"foo","bar":"bar"}
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```
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[fastify-plugin]: https://github.com/fastify/fastify-plugin
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