spring 在子上下文中覆盖父上下文中定义的 bean
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Overriding the bean defined in parent context in a child context
提问by Aravind Yarram
Our app has a requirement to support multi-tenancy. Each of the boarded customer might potentially override 1 or more beans or some properties of a bean defined at the core platform level (common code/definitions). I am wondering what is the best way to handle this.
我们的应用程序需要支持多租户。每个登上的客户可能会覆盖 1 个或多个 bean 或在核心平台级别定义的 bean 的某些属性（公共代码/定义）。我想知道处理这个问题的最佳方法是什么。
回答by skaffman
Spring allows you to redefine the same bean name multiple times, and takes the last bean definition processed for a given name to be the one that wins. So for example, your could have an XML file defining your core beans, and import that in a client-specific XML file, which also redefines some of those beans. It's a bit fragile, though, since there's no mechanism to specifically say "this bean definition is an override".
Spring 允许您多次重新定义相同的 bean 名称，并将为给定名称处理的最后一个 bean 定义作为获胜者。例如，您可以有一个定义核心 bean 的 XML 文件，并将其导入到特定于客户端的 XML 文件中，该文件还会重新定义其中一些 bean。但是，它有点脆弱，因为没有机制专门说“这个 bean 定义是一个覆盖”。
I've found that the cleanest way to handle this is using the new @Bean-syntax introduced in Spring 3. Rather than defining beans as XML, you define them in Java. So your core beans would be defined in one @Bean-annotated class, and your client configs would subclass that, and override the appropriate beans. This allows you to use standard java @Overrideannotations, explicitly indicating that a given bean definition is being overridden.
我发现处理这个问题的最干净的方法是使用Spring 3 中引入的新@Bean-syntax。不是将 bean 定义为 XML，而是在 Java 中定义它们。因此，您的核心 bean 将在一个带@Bean注释的类中定义，您的客户端配置将子类化该类，并覆盖适当的 bean。这允许您使用标准的 java@Override注释，明确指示给定的 bean 定义正在被覆盖。
