Service Locator Pattern

Martin Fowler 的 Inversion of Control Containers and the Dependency Injection pattern 中提到的。

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basic idea: service locator is an object that knows how to get hold of all of the services that an application might need.（我是否可以理解为一个应用可能有 DaoLocator 和 ServiceLocator 来分层管理，而不是只有一个 locator 管理全部组件？）

A well-known object that other objects can use to find common objects and services is known as a registry. Therefore, no doubt，ServiceLocator is a registry.

如果 Service 包含一个 DaoLocator，也可以实现注入的效果。

segregated ([‘segrigeitid], 种族隔离的) locator：如果不想把所有的 DaoLocator 接口都暴露给 XXXService，可以写成 DaoLocator implements AppleDaoLocator，然后 AppleService 只包含 AppleDaoLocator。

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如果要深入研究的话，先看下这篇 Service Locator is an Anti-Pattern.