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<!DOCTYPE html>
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<title>依赖注入手册 | Midway</title>
<meta name="description" content="面向未来的 Web 全栈应用开发框架">
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<div id="app" data-server-rendered="true"><div class="theme-container"><header class="navbar"><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/midway/" class="home-link router-link-active"><!----> <span class="site-name">Midway</span></a> <div class="links" style="max-width:nullpx;"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="/midway/" class="nav-link">首页</a></div><div class="nav-item"><a href="/midway/guide.html" class="nav-link">使用文档</a></div><div class="nav-item"><a href="/midway/ioc.html" aria-current="page" class="nav-link router-link-exact-active router-link-active">依赖注入手册</a></div><div class="nav-item"><a href="/midway/tool_set.html" class="nav-link">工具集</a></div><div class="nav-item"><a href="/midway/ts_start.html" class="nav-link">TS 新手指南</a></div><div class="nav-item"><a href="http://midwayjs.org/midway/api-reference/globals.html" target="_blank" rel="noopener noreferrer" class="nav-link external">
API
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">MidwayJs 系列产品</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>框架</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/midway/" class="nav-link">Midway - 面向未来的 Web 全栈框架</a></li></ul></li><li class="dropdown-item"><h4>应用管理</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="http://midwayjs.org/pandora/" target="_blank" rel="noopener noreferrer" class="nav-link external">
Pandora.js - Node.js 应用管理器
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></li></ul></li><li class="dropdown-item"><h4>监控产品</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://github.com/midwayjs/sandbox-docker" target="_blank" rel="noopener noreferrer" class="nav-link external">
Sandbox - 私有化 Node.js 监控产品
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></li></ul></li><li class="dropdown-item"><h4>Node.js 依赖注入模块</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="http://midwayjs.org/injection" target="_blank" rel="noopener noreferrer" class="nav-link external">
Injection - 让你的应用用上 IoC，体验依赖注入的感觉
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">Languages</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/midway/ioc.html" aria-current="page" class="nav-link router-link-exact-active router-link-active">zh-CN</a></li><li class="dropdown-item"><!----> <a href="/midway/en/ioc.html" class="nav-link">en-US</a></li></ul></div></div> <!----></nav></div></header> <div class="sidebar-mask"></div> <div class="sidebar"><nav class="nav-links"><div class="nav-item"><a href="/midway/" class="nav-link">首页</a></div><div class="nav-item"><a href="/midway/guide.html" class="nav-link">使用文档</a></div><div class="nav-item"><a href="/midway/ioc.html" aria-current="page" class="nav-link router-link-exact-active router-link-active">依赖注入手册</a></div><div class="nav-item"><a href="/midway/tool_set.html" class="nav-link">工具集</a></div><div class="nav-item"><a href="/midway/ts_start.html" class="nav-link">TS 新手指南</a></div><div class="nav-item"><a href="http://midwayjs.org/midway/api-reference/globals.html" target="_blank" rel="noopener noreferrer" class="nav-link external">
API
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">MidwayJs 系列产品</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>框架</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/midway/" class="nav-link">Midway - 面向未来的 Web 全栈框架</a></li></ul></li><li class="dropdown-item"><h4>应用管理</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="http://midwayjs.org/pandora/" target="_blank" rel="noopener noreferrer" class="nav-link external">
Pandora.js - Node.js 应用管理器
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></li></ul></li><li class="dropdown-item"><h4>监控产品</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://github.com/midwayjs/sandbox-docker" target="_blank" rel="noopener noreferrer" class="nav-link external">
Sandbox - 私有化 Node.js 监控产品
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></li></ul></li><li class="dropdown-item"><h4>Node.js 依赖注入模块</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="http://midwayjs.org/injection" target="_blank" rel="noopener noreferrer" class="nav-link external">
Injection - 让你的应用用上 IoC，体验依赖注入的感觉
<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title">Languages</span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/midway/ioc.html" aria-current="page" class="nav-link router-link-exact-active router-link-active">zh-CN</a></li><li class="dropdown-item"><!----> <a href="/midway/en/ioc.html" class="nav-link">en-US</a></li></ul></div></div> <!----></nav> <ul class="sidebar-links"><li><div class="sidebar-group first"><p class="sidebar-heading open"><span>依赖注入手册</span> <!----></p> <ul class="sidebar-group-items"><li><a href="/midway/ioc.html#背景" class="sidebar-link">背景</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#ioc-概览" class="sidebar-link">IoC 概览</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#使用-injection-解耦" class="sidebar-link">使用 injection 解耦</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#获取-ioc-容器" class="sidebar-link">获取 IoC 容器</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#对象定义" class="sidebar-link">对象定义</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#绑定对象定义" class="sidebar-link">绑定对象定义</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#普通情况下获取对象" class="sidebar-link">普通情况下获取对象</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#使用装饰器注入" class="sidebar-link">使用装饰器注入</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a href="/midway/ioc.html#provide" class="sidebar-link">@provide()</a></li><li class="sidebar-sub-header"><a href="/midway/ioc.html#inject" class="sidebar-link">@inject()</a></li></ul></li><li><a href="/midway/ioc.html#对象-id" class="sidebar-link">对象 id</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#构造器注入" class="sidebar-link">构造器注入</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#配置作用域" class="sidebar-link">配置作用域</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#异步初始化" class="sidebar-link">异步初始化</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#动态函数注入" class="sidebar-link">动态函数注入</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#注入已有对象" class="sidebar-link">注入已有对象</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/midway/ioc.html#通过依赖图排错" class="sidebar-link">通过依赖图排错</a><ul class="sidebar-sub-headers"></ul></li></ul></div></li></ul> </div> <div class="page"> <div class="content"><h1 id="依赖注入手册"><a href="#依赖注入手册" class="header-anchor">#</a> 依赖注入手册</h1> <div class="warning custom-block"><p class="custom-block-title">WARNING</p> <p>本文档已迁移至 <a href="https://midwayjs.org/injection/guide.html" target="_blank" rel="noopener noreferrer">新地址<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a>，此处内容不再继续更新。</p></div> <p>Midway 中使用了非常多的依赖注入的特性，通过装饰器的轻量特性，让依赖注入变的优雅，从而让开发过程变的便捷有趣。</p> <h2 id="背景"><a href="#背景" class="header-anchor">#</a> 背景</h2> <p>midway 默认使用 <a href="http://web.npm.alibaba-inc.com/package/injection" target="_blank" rel="noopener noreferrer">injection<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 这个包来做依赖注入，这个包也是 MidwayJs 团队根据业界已有的实现而产出的自研产品，它除了常见的依赖了注入之外，还满足了 Midway 自身的一些特殊需求。</p> <p>这篇文章不仅仅是 IoC 体系的介绍，也是属于 <a href="http://web.npm.alibaba-inc.com/package/injection" target="_blank" rel="noopener noreferrer">injection<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 这个包的一份使用文档。</p> <p>你不仅可以在 Midway 的开发过程中用到它，如果你希望，它也可以在你的模块开发中帮助到你，它可以单独使用，也可以和现有框架集成，比如 <code>koa</code>, <code>thinkjs</code> 等。</p> <div class="tip custom-block"><p class="custom-block-title">TIP</p> <p>我们在 midway 包上做了自动导出，所以 injection 包中的模块，都能从 midway 中获取到。
import {Container} from 'injection' 和 import {Container} from 'midway' 是一样的。</p></div> <h2 id="ioc-概览"><a href="#ioc-概览" class="header-anchor">#</a> IoC 概览</h2> <p>IoC(<a href="https://en.wikipedia.org/wiki/Inversion_of_control" target="_blank" rel="noopener noreferrer">Inversion of control<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a>) 控制反转，是 Java Spring 中非常重要的思想和核心，有不少人是第一次听说，也不禁会有许多疑问。</p> <ul><li>什么是控制反转？</li> <li>什么是依赖注入？</li> <li>它们之间有什么关系？</li></ul> <p>软件中的对象就像齿轮一样，协同工作，但是互相耦合，一个零件不能正常工作，整个系统就崩溃了。这是一个强耦合的系统。</p> <p>现在，伴随着工业级应用的规模越来越庞大，对象之间的依赖关系也越来越复杂，经常会出现对象之间的多重依赖性关系，因此，架构师和设计师对于系统的分析和设计，将面临更大的挑战。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token comment">// 常见的依赖</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span><span class="token constant">A</span><span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'./A'</span><span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span><span class="token constant">B</span><span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'./B'</span><span class="token punctuation">;</span>
<span class="token keyword">class</span> <span class="token class-name">C</span> <span class="token punctuation">{</span>
<span class="token function">consturctor</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>a <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">A</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>b <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">B</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>这里的 A 被 B 和 C 所依赖，而且在构造器需要进行实例化操作，这样的依赖关系在测试中会非常麻烦。这个依赖，一般被叫做 "耦合"，而耦合度过高的系统，必然会出现牵一发而动全身的情形。</p> <p>为了解决对象间耦合度过高的问题，软件专家 Michael Mattson 提出了 IoC 理论，用来实现对象之间的“解耦”。</p> <p>控制反转（Inversion of Control）是一种是面向对象编程中的一种设计原则，用来减低计算机代码之间的耦合度。</p> <h2 id="使用-injection-解耦"><a href="#使用-injection-解耦" class="header-anchor">#</a> 使用 injection 解耦</h2> <p>如果你使用了 midway，这些创建的过程将会自动完成，这里为了更好理解，我们将从头开始展示。</p> <p>首先是安装依赖：</p> <div class="language-bash extra-class"><pre class="language-bash"><code><span class="token function">npm</span> i injection --save
</code></pre></div><p>然后我们将上面的代码进行解耦。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token comment">// 使用 IoC</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span>Container<span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'injection'</span><span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span><span class="token constant">A</span><span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'./A'</span><span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span><span class="token constant">B</span><span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'./B'</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> container <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Container</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token constant">A</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token constant">B</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">class</span> <span class="token class-name">C</span> <span class="token punctuation">{</span>
<span class="token function">consturctor</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>a <span class="token operator">=</span> container<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span><span class="token string">'A'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>b <span class="token operator">=</span> container<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span><span class="token string">'B'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>这里的 <code>container</code> 就是 IoC 容器，是依赖注入这种设计模式的一种实现，使得 C 和 A, B 没有了强耦合关系，甚至，我们可以把 C 也交给 IoC 容器，所以，IoC 容器成了整个系统的关键核心。</p> <div class="tip custom-block"><p class="custom-block-title">注意</p> <p>IoC 容器就像是一个对象池，管理这每个对象实例的信息（Class Definition），所以用户无需关心什么时候创建，当用户希望拿到对象的实例 (Object Instance) 时，可以直接拿到实例，容器会 <strong>自动将所有依赖的对象都自动实例化</strong>。</p></div> <h2 id="获取-ioc-容器"><a href="#获取-ioc-容器" class="header-anchor">#</a> 获取 IoC 容器</h2> <p>所谓的容器就是一个对象池，它会在应用初始化的时候自动处理类的依赖，并将类进行实例化。比如下面的 <code>UserService</code> 类，在经过容器初始化之后，会自动实例化，并且对 <code>userModel</code> 进行赋值，看不到实例化的过程。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token keyword">class</span> <span class="token class-name">UserService</span> <span class="token punctuation">{</span>
<span class="token keyword">private</span> userModel<span class="token punctuation">;</span>
<span class="token keyword">async</span> <span class="token function">getUser</span><span class="token punctuation">(</span><span class="token parameter">uid</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token comment">// TODO</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>Midway 内部使用了自动扫描的机制，在应用初始化之前，会扫描所有的文件，包含装饰器的文件会 <strong>自动绑定</strong> 到容器。</p> <p>injection 的容器有几种：</p> <ul><li>AppliationContext 基础容器，提供了基础的增加定义和根据定义获取对象实例的能力</li> <li>Container 用的最多的容器，做了上层封装，通过 bind 函数能够方便的生成类定义，midway 从此类开始扩展</li> <li>RequestContext 用于请求链路上的容器，会自动销毁对象并依赖另一个容器创建实例。</li></ul> <p>其中 <code>Container</code> 是我们最常用的容器，下面的代码就是创建一个容器。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token keyword">import</span> <span class="token punctuation">{</span>Container<span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'injection'</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> container <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Container</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><h2 id="对象定义"><a href="#对象定义" class="header-anchor">#</a> 对象定义</h2> <p>一个对象的基本元信息，比如名字，是否异步，有哪些属性，依赖等等，我们把这些信息组合到一起，形成一个对象定义。</p> <p>对象定义往往表现在他的基础类型上， injection 内置了名为 <code>ObjectDefinition</code> 的对象定义类，它包含一系列属性，比如：</p> <ul><li>有哪些属性</li> <li>是否有依赖的对象</li> <li>创建时是否是异步的</li> <li>初始化方法是哪个</li> <li>是否自动装配</li></ul> <p>以上只是列举了一小部分，通过这个定义，容器就可以将一个对象简单的创建出来。</p> <p><code>ObjectDefinition</code> 的具体属性文档，可以在 <a href="https://midwayjs.org/injection/api-reference/classes/objectdefinition.html" target="_blank" rel="noopener noreferrer">这里看到<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a></p> <h2 id="绑定对象定义"><a href="#绑定对象定义" class="header-anchor">#</a> 绑定对象定义</h2> <p>我们在创建容器之后，将会往这个容器中添加一些对象定义，这样容器才能将对应对象创建出来。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token keyword">class</span> <span class="token class-name">UserService</span> <span class="token punctuation">{</span>
<span class="token keyword">private</span> userModel<span class="token punctuation">;</span>
<span class="token keyword">async</span> <span class="token function">getUser</span><span class="token punctuation">(</span><span class="token parameter">uid</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token comment">// TODO</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">// 内部代码</span>
<span class="token keyword">const</span> container <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Container</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 创建容器</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token string">'userService'</span><span class="token punctuation">,</span> UserService<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 可以在绑定的时候传一个名字作为 key</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span>UserService<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 也可以直接传入 Class，自动分析对象的元信息生成对象定义</span>
</code></pre></div><p><code>bind</code> 方法通过传入类型，自动分析类型上面包含的元信息，具体的 API 参数可以查看<a href="https://midwayjs.org/injection/api-reference/classes/container.html#bind" target="_blank" rel="noopener noreferrer">这里<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a>。</p> <h2 id="普通情况下获取对象"><a href="#普通情况下获取对象" class="header-anchor">#</a> 普通情况下获取对象</h2> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token comment">//... 省略绑定逻辑</span>
<span class="token keyword">const</span> userService <span class="token operator">=</span> <span class="token keyword">await</span> container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'userService'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 这里根据 key 获取对象</span>
<span class="token keyword">const</span> user <span class="token operator">=</span> <span class="token keyword">await</span> userService<span class="token punctuation">.</span><span class="token function">getUser</span><span class="token punctuation">(</span><span class="token string">'123'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 如果对象以及对象的依赖中没有异步的情况，也可以同步获取</span>
<span class="token keyword">const</span> userService <span class="token operator">=</span> container<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span><span class="token string">'userService'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> user <span class="token operator">=</span> userService<span class="token punctuation">.</span><span class="token function">getUser</span><span class="token punctuation">(</span><span class="token string">'123'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">//...</span>
</code></pre></div><p>只有绑定过的对象定义才能通过 <code>get</code> 和 <code>getAsync</code> 方法创建出来。</p> <p>如果一个对象依赖了另一个对象，那么在创建的时候，依赖的对象都会被自动创建并且在容器中管理起来。</p> <div class="tip custom-block"><p class="custom-block-title">Tip</p> <p>由于 Node.js 中大多对象或者依赖都需要支持异步的情况，所以一般情况下我们都使用 <code>getAsync</code> 方法。</p></div> <h2 id="使用装饰器注入"><a href="#使用装饰器注入" class="header-anchor">#</a> 使用装饰器注入</h2> <p>如果每次代码都需要手动绑定，然后通过 <code>get/getAsync</code> 方法拿到对应的对象，那将会非常繁琐，由于 在设计之初 midway/injection 体系就基于 ts，参考了业界的 IoC 实现，完成了属于自己的依赖注入能力，主要是通过 <code>@provide</code> 和 <code>@inject</code> 两个装饰器来完成绑定定义和自动注入属性，大大简化了代码量。</p> <div class="tip custom-block"><p class="custom-block-title">TIP</p> <p>由于使用了依赖注入体系，我们希望所有的业务代码都通过 class 语法来完成</p></div> <div class="language-typescript extra-class"><pre class="language-typescript"><code>@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">UserService</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
userModel<span class="token punctuation">;</span>
<span class="token keyword">async</span> <span class="token function">getUser</span><span class="token punctuation">(</span><span class="token parameter">userId</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">await</span> <span class="token keyword">this</span><span class="token punctuation">.</span>userModel<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span>userId<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>我们可以看到业务代码的样子和以往有着一些不同。</p> <ul><li>类加了装饰器，同时直接导出，不需要关心如何实例化</li> <li>属性加了装饰器，但是没有任何初始化以及赋值的操作即可使用</li></ul> <h3 id="provide"><a href="#provide" class="header-anchor">#</a> @provide()</h3> <p>有了 <code>@provide()</code> 装饰器，就可以简化绑定，被 IoC 容器自动扫描，并绑定定义到容器上，对应的逻辑是 <a href="#%E7%BB%91%E5%AE%9A%E5%AF%B9%E8%B1%A1%E5%AE%9A%E4%B9%89">绑定对象定义</a>。</p> <p><code>@provide(id?)</code> 的参数为对象 id，可选。</p> <div class="tip custom-block"><p class="custom-block-title">注意</p> <p>@provide 装饰器是用于自动被 IoC 容器装载。</p></div> <h3 id="inject"><a href="#inject" class="header-anchor">#</a> @inject()</h3> <p><code>@inject()</code> 的作用是将容器中的定义实例化成一个对象，并且绑定到属性中，这样，在调用的时候就可以访问到该属性。</p> <div class="warning custom-block"><p class="custom-block-title">注意</p> <p>注入的时机为构造器（new）之后，所以在构造方法(constructor)中是无法获取注入的属性的，如果要获取注入的内容，可以使用 <a href="#%E6%9E%84%E9%80%A0%E5%99%A8%E6%B3%A8%E5%85%A5">构造器注入</a>。</p></div> <p>父类的属性使用 <code>@inject()</code> 装饰器装饰，子类实例会得到装饰后的属性。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code><span class="token keyword">class</span> <span class="token class-name">Parent</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
katana1<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">class</span> <span class="token class-name">Child</span> <span class="token keyword">extends</span> <span class="token class-name">Parent</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
katana2<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">class</span> <span class="token class-name">Grandson</span> <span class="token keyword">extends</span> <span class="token class-name">Child</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
katana3<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p><code>Grandson</code> 的实例 <code>grandson</code> 拥有 <code>@inject()</code> 装饰器注入的
<code>grandson.katana3</code>, <code>grandson.katana2</code>, <code>grandson.katana1</code> 属性。</p> <p>实现时，会查找 <code>Gradson</code> 的原型链，遍历原型链上所有用 <code>@inject()</code> 装饰的属性，运行装饰器，注入相应的属性。</p> <p>查找类的原型使用 <a href="https://github.com/rbuckton/reflect-metadata" target="_blank" rel="noopener noreferrer">reflect-metadata<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 仓库的 <a href="https://github.com/rbuckton/reflect-metadata/blob/c2dbe1d02ceb9987f9002eedf0cdb21d74de0019/Reflect.ts#L1553-L1583" target="_blank" rel="noopener noreferrer">OrdinaryGetPrototypeOf<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 方法，使用 <code>recursiveGetPrototypeOf</code> 方法以数组形式返回该类的所有原型。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code><span class="token keyword">function</span> <span class="token function">recursiveGetPrototypeOf</span><span class="token punctuation">(</span><span class="token parameter">target<span class="token operator">:</span> <span class="token builtin">any</span></span><span class="token punctuation">)</span><span class="token operator">:</span> <span class="token builtin">any</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span>
<span class="token keyword">const</span> properties <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> parent <span class="token operator">=</span> <span class="token function">ordinaryGetPrototypeOf</span><span class="token punctuation">(</span>target<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">while</span> <span class="token punctuation">(</span>parent <span class="token operator">!==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
properties<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span>parent<span class="token punctuation">)</span><span class="token punctuation">;</span>
parent <span class="token operator">=</span> <span class="token function">ordinaryGetPrototypeOf</span><span class="token punctuation">(</span>parent<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">return</span> properties<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><h2 id="对象-id"><a href="#对象-id" class="header-anchor">#</a> 对象 id</h2> <p>在默认情况下，injection 会将类名变为 <code>驼峰</code> 形式作为对象 id，这样你可以通过容器获取实例。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code>container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'userService'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 根据字符串 id 获取实例</span>
container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span>UserService<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 传入类名，自动根据类目获取实例</span>
</code></pre></div><p>而默认情况下，Midway 的依赖注入使用的是 <code>byName</code> ，只要同名，就会自动进行注入。</p> <p>而在某些场景下，用户希望注入不同的实例，这个时候可以对默认生成的 id 进行修改。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code>@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token string">'uModel'</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">UserModel</span> <span class="token punctuation">{</span>
<span class="token punctuation">}</span>
@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token string">'user'</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">UserService</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token string">'uModel'</span><span class="token punctuation">)</span>
userModel<span class="token punctuation">;</span>
<span class="token keyword">async</span> <span class="token function">getUser</span><span class="token punctuation">(</span><span class="token parameter">userId</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">await</span> <span class="token keyword">this</span><span class="token punctuation">.</span>userModel<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span>userId<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">// 使用修改之后的 id 获取对象</span>
<span class="token keyword">const</span> userService <span class="token operator">=</span> <span class="token keyword">await</span> container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'user'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>同理，在使用 <code>@inject</code> 的时候也可以使用不同的 id。</p> <h2 id="构造器注入"><a href="#构造器注入" class="header-anchor">#</a> 构造器注入</h2> <p>除了标准的属性注入方法之外，midway 在一定程度上支持了构造器注入的方式，来让一些应用或者三方包平稳过度。</p> <p>同样还是使用 <code>@inject</code> 装饰器。</p> <div class="language-ts extra-class"><pre class="language-ts"><code>@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">A</span> <span class="token punctuation">{</span>
config <span class="token operator">=</span> <span class="token punctuation">{</span>
c<span class="token operator">:</span> <span class="token number">20</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">B</span> <span class="token punctuation">{</span>
config <span class="token operator">=</span> <span class="token punctuation">{</span>
c<span class="token operator">:</span> <span class="token number">40</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">BaseService</span> <span class="token punctuation">{</span>
config<span class="token punctuation">;</span>
plugin2<span class="token punctuation">;</span>
<span class="token keyword">constructor</span><span class="token punctuation">(</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span> a<span class="token punctuation">,</span>
@<span class="token function">config</span><span class="token punctuation">(</span><span class="token string">'hello'</span><span class="token punctuation">)</span> config<span class="token punctuation">,</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span> b<span class="token punctuation">,</span>
@<span class="token function">plugin</span><span class="token punctuation">(</span><span class="token string">'plugin2'</span><span class="token punctuation">)</span> plugin2
<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>config <span class="token operator">=</span> Object<span class="token punctuation">.</span><span class="token function">assign</span><span class="token punctuation">(</span>config<span class="token punctuation">,</span> <span class="token punctuation">{</span>
c<span class="token operator">:</span> a<span class="token punctuation">.</span>config<span class="token punctuation">.</span>c <span class="token operator">+</span> b<span class="token punctuation">.</span>config<span class="token punctuation">.</span>c <span class="token operator">+</span> config<span class="token punctuation">.</span>c
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>plugin2 <span class="token operator">=</span> plugin2<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>在一个类的构造器中，我们可以还可以使用其他的类似 <code>@config</code>, <code>@plugin</code>, <code>@logger</code> 等装饰器。只要是通过 IoC 管理的对象，都能够被自动依赖和注入。</p> <h2 id="配置作用域"><a href="#配置作用域" class="header-anchor">#</a> 配置作用域</h2> <p>在 injection 体系中，有三种作用域。</p> <ul><li>Singleton 单例，全局唯一（进程级别）</li> <li>Request <strong>默认</strong>，请求作用域，生命周期随着请求链路，在请求链路上唯一，请求结束立即销毁</li> <li>Prototype 原型作用域，每次调用都会重复创建一个新的对象</li></ul> <p>在这三种作用域中，midway 的默认作用域为 <strong>请求作用域</strong>，这也意味着，如果我们需要将一个对象定义为其他两种作用域，需要额外的配置。</p> <p>injection 提供了 <code>@scope</code> 装饰器来定义一个类的作用域。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code>@<span class="token function">scope</span><span class="token punctuation">(</span>ScopeEnum<span class="token punctuation">.</span>Prototype<span class="token punctuation">)</span>
@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token string">'petrol'</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">PetrolEngine</span> <span class="token keyword">implements</span> <span class="token class-name">Engine</span> <span class="token punctuation">{</span>
capacity <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
@<span class="token function">scope</span><span class="token punctuation">(</span>ScopeEnum<span class="token punctuation">.</span>Singleton<span class="token punctuation">)</span>
@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token string">'diesel'</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">DieselEngine</span> <span class="token keyword">implements</span> <span class="token class-name">Engine</span> <span class="token punctuation">{</span>
capacity <span class="token operator">=</span> <span class="token number">20</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// in IoC Container</span>
<span class="token function">assert</span><span class="token punctuation">(</span>container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'petrol'</span><span class="token punctuation">)</span> <span class="token operator">===</span> container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'petrol'</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">// false</span>
<span class="token function">assert</span><span class="token punctuation">(</span>container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'diesel'</span><span class="token punctuation">)</span> <span class="token operator">===</span> container<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'diesel'</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">// true</span>
</code></pre></div><p class="warning">
插件，在 midway 中为单例，不可配置。
</p> <h2 id="异步初始化"><a href="#异步初始化" class="header-anchor">#</a> 异步初始化</h2> <p>在某些情况下，我们需要一个实例在被其他依赖调用前需要初始化，如果这个初始化只是读取某个文件，那么可以写成同步方式，而如果这个初始化是从远端拿取数据或者连接某个服务，这个情况下，普通的同步代码就非常的难写。</p> <p>midway 提供了异步初始化的能力，通过 <code>@init</code> 标签来管理初始化方法。</p> <p><code>@init</code> 方法目前只能是一个。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code>@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">BaseService</span> <span class="token punctuation">{</span>
@<span class="token function">config</span><span class="token punctuation">(</span><span class="token string">'hello'</span><span class="token punctuation">)</span>
config<span class="token punctuation">;</span>
@<span class="token function">plugin</span><span class="token punctuation">(</span><span class="token string">'plugin2'</span><span class="token punctuation">)</span>
plugin2<span class="token punctuation">;</span>
@<span class="token function">init</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">async</span> <span class="token function">init</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">await</span> <span class="token keyword">new</span> <span class="token class-name">Promise</span><span class="token punctuation">(</span><span class="token parameter">resolve</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
<span class="token function">setTimeout</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>config<span class="token punctuation">.</span>c <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
<span class="token function">resolve</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><div class="warning custom-block"><p class="custom-block-title">注意</p> <p>@async 装饰器已废弃，所有的 init 方法默认都会异步，同步初始化可以直接在构造器执行，此装饰器没有意义。</p></div> <p>只要在方法上标记 <code>@init</code> 装饰器之后，这个时候会自动在实例化之后，通过异步的来调用 <code>@init</code> 标记的方法。</p> <h2 id="动态函数注入"><a href="#动态函数注入" class="header-anchor">#</a> 动态函数注入</h2> <p>在某些场景下，我们需要函数作为某个逻辑动态执行，而 IoC 中的对象属性则都是已经创建好的，无法满足动态的逻辑需求。</p> <p>比如你需要一个工厂函数，根据不同的场景返回不同的实例，也可能有一个三方包，是个函数，在业务中想要直接调用，种种的场景下，你就需要直接注入一个函数，并且在函数中拿到上下文。</p> <p>标准的函数注入样例。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code><span class="token keyword">export</span> <span class="token keyword">function</span> <span class="token function">contextHandler</span><span class="token punctuation">(</span><span class="token parameter">context</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">async</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
<span class="token comment">// const xxx = context.getAsync('xxxx');</span>
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token function">providerWrapper</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
<span class="token punctuation">{</span>
id<span class="token operator">:</span> <span class="token string">'contextHandler'</span><span class="token punctuation">,</span>
provider<span class="token operator">:</span> contextHandler<span class="token punctuation">,</span>
<span class="token punctuation">}</span>
<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>使用端。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code>@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">BaseService</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token function-variable function">contextHandler</span><span class="token operator">:</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token builtin">boolean</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>midway 通过 <code>providerWrapper</code> 函数来包裹一个函数，并且指定提供的 key，供其他 IoC 对象使用。由于函数直接传递了一个 context 对象，可以轻松的通过此对象拿到所需的其他对象，而不需要管理依赖。</p> <p>函数注入大多数为了创建一个简单的工厂。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code><span class="token keyword">export</span> <span class="token keyword">function</span> <span class="token function">adapterFactory</span><span class="token punctuation">(</span><span class="token parameter">context<span class="token operator">:</span> IApplicationContext</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">async</span> <span class="token punctuation">(</span><span class="token parameter">adapterName<span class="token operator">:</span> <span class="token builtin">string</span></span><span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>adapterName <span class="token operator">===</span> <span class="token string">'google'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">await</span> context<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'googleAdapter'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>adapterName <span class="token operator">===</span> <span class="token string">'baidu'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">await</span> context<span class="token punctuation">.</span><span class="token function">getAsync</span><span class="token punctuation">(</span><span class="token string">'baiduAdapter'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// return await context.getAsync(adapterName + 'Adapter');</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token function">providerWrapper</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
<span class="token punctuation">{</span>
id<span class="token operator">:</span> <span class="token string">'adapterFactory'</span><span class="token punctuation">,</span>
provider<span class="token operator">:</span> adapterFactory<span class="token punctuation">,</span>
<span class="token punctuation">}</span>
<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>这样在业务中，可以直接来使用了。</p> <div class="language-typescript extra-class"><pre class="language-typescript"><code>
@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">BaseService</span> <span class="token punctuation">{</span>
@<span class="token function">config</span><span class="token punctuation">(</span><span class="token string">'adapterName'</span><span class="token punctuation">)</span>
adapterName<span class="token punctuation">;</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token string">'adapterFactory'</span><span class="token punctuation">)</span>
factory<span class="token punctuation">;</span>
adapter<span class="token operator">:</span> Adapter<span class="token punctuation">;</span>
@<span class="token function">init</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">async</span> <span class="token function">init</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">this</span><span class="token punctuation">.</span>adapter <span class="token operator">=</span> <span class="token keyword">await</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">factory</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>adapterName<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><div class="tip custom-block"><p class="custom-block-title">TIP</p> <p>这个函数可以是异步的 (async)。</p></div> <p>再举个例子，比如如果应用希望自己使用 sequelize， 而 sequelize 的创建 model 的过程是个异步操作，代码就可以这么写：</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token keyword">import</span> <span class="token punctuation">{</span> providerWrapper<span class="token punctuation">,</span> IApplicationContext <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'midway'</span><span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token operator">*</span> <span class="token keyword">as</span> Sequelize <span class="token keyword">from</span> <span class="token string">'sequelize'</span><span class="token punctuation">;</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span> Sequelize <span class="token keyword">as</span> SequelizeInstance <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'sequelize'</span><span class="token punctuation">;</span>
<span class="token comment">// 可以直接写 async 方法</span>
<span class="token keyword">export</span> <span class="token keyword">async</span> <span class="token keyword">function</span> <span class="token function">factory</span><span class="token punctuation">(</span><span class="token parameter">context<span class="token operator">:</span> IApplicationContext</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">const</span> instance <span class="token operator">=</span> <span class="token keyword">await</span> context<span class="token punctuation">.</span>getAsync<span class="token operator"><</span>SequelizeInstance<span class="token operator">></span><span class="token punctuation">(</span><span class="token string">'coreDB'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> UiKeyTraceModel <span class="token operator">=</span> instance<span class="token punctuation">.</span><span class="token function">define</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> <span class="token punctuation">{</span>
gmtCreate<span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token keyword">type</span><span class="token operator">:</span> Sequelize<span class="token punctuation">.</span><span class="token constant">DATE</span><span class="token punctuation">,</span>
allowNull<span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">,</span>
field<span class="token operator">:</span> <span class="token string">'gmt_create'</span><span class="token punctuation">,</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
gmtModified<span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token keyword">type</span><span class="token operator">:</span> Sequelize<span class="token punctuation">.</span><span class="token constant">DATE</span><span class="token punctuation">,</span>
allowNull<span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">,</span>
field<span class="token operator">:</span> <span class="token string">'gmt_modified'</span><span class="token punctuation">,</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token punctuation">{</span>
timestamps<span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">,</span>
createdAt<span class="token operator">:</span> <span class="token string">'gmt_create'</span><span class="token punctuation">,</span>
updatedAt<span class="token operator">:</span> <span class="token string">'gmt_modified'</span><span class="token punctuation">,</span>
freezeTableName<span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">,</span>
tableName<span class="token operator">:</span> <span class="token string">'xxxx'</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">return</span> UiKeyTraceModel<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token function">providerWrapper</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
<span class="token punctuation">{</span>
id<span class="token operator">:</span> <span class="token string">'keyTraceModel'</span><span class="token punctuation">,</span>
provider<span class="token operator">:</span> factory
<span class="token punctuation">}</span>
<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>通过 <code>providerWrapper</code> 我们将一个原本的函数写法进行了包裹，和现有的依赖注入体系可以融合到一起，让容器能够统一管理。</p> <h2 id="注入已有对象"><a href="#注入已有对象" class="header-anchor">#</a> 注入已有对象</h2> <p>有时候，应用已经有现有的实例，而不是类，比如引入了一个第三库，这个时候如果希望对象能够被其他 IoC 容器中的实例引用，也可以通过增加对象的方式进行处理。</p> <p>我们拿常见的 http 请求库 <a href="https://www.npmjs.com/package/urllib" target="_blank" rel="noopener noreferrer">urllib<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 来举例。</p> <p>假如我们希望在不同的类中来使用，并且不通过 require 的方式，你需要在容器的入口通过 <a href="https://midwayjs.org/injection/api-reference/classes/container.html#registerobject" target="_blank" rel="noopener noreferrer">registerobject<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 方法添加这个对象。</p> <p>在添加的时候需要给出一个 key，方便其他类中注入。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token comment">// in global file</span>
<span class="token keyword">import</span> <span class="token operator">*</span> <span class="token keyword">as</span> urllib <span class="token keyword">from</span> <span class="token string">'urllib'</span><span class="token punctuation">;</span>
container<span class="token punctuation">.</span><span class="token function">registerobject</span><span class="token punctuation">(</span><span class="token string">'httpclient'</span><span class="token punctuation">,</span> urllib<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>这个时候就可以在任意的类中通过 <code>@inject</code> 来使用了。</p> <div class="language-ts extra-class"><pre class="language-ts"><code>@<span class="token function">provide</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">class</span> <span class="token class-name">BaseService</span> <span class="token punctuation">{</span>
@<span class="token function">inject</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
httpclient<span class="token punctuation">;</span>
<span class="token keyword">async</span> <span class="token function">getUser</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> <span class="token keyword">await</span> <span class="token keyword">this</span><span class="token punctuation">.</span>httpclient<span class="token punctuation">.</span><span class="token function">request</span><span class="token punctuation">(</span><span class="token string">'/api/getuser'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><div class="tip custom-block"><p class="custom-block-title">TIP</p> <p>在 midway 中可以在 src/app.ts 中进行添加。</p></div> <h2 id="通过依赖图排错"><a href="#通过依赖图排错" class="header-anchor">#</a> 通过依赖图排错</h2> <p>在业务代码中，我们可能会碰到依赖注入不生效或者作用域配置错误的问题，这个时候由于容器管理的问题显得不透明，用户也不太清楚容器里有哪些东西，分别依赖了什么。</p> <p>我们提供了一个依赖树生成的方法，目前可以通过它生成文本形式的图形。</p> <div class="language-ts extra-class"><pre class="language-ts"><code><span class="token keyword">const</span> container <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Container</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span>UserService<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span>UserController<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">container</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span>DbAPI<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> newTree <span class="token operator">=</span> <span class="token keyword">await</span> container<span class="token punctuation">.</span><span class="token function">dumpDependency</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token builtin">console</span><span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>newTree<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><p>通过 <code>dumpDependency</code> 方法生成的文本，可以直接在 <a href="http://viz-js.com/" target="_blank" rel="noopener noreferrer">viz-js<svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg></a> 渲染为图案，方便排查问题。</p> <p>也可以通过安装 <code>graphviz</code> 等工具将文本树转化为图片形式。</p> <div class="tip custom-block"><p class="custom-block-title">TIP</p> <p>midway 在启动时会将依赖树生成到 /run 目录下，方便排错。</p></div></div> <div class="page-edit"><!----> <!----></div> <!----> </div> <!----></div></div>
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