从自定义类获取spring配置值 [英] Acquiring a spring configuration value from a custom class

问题描述

我正在考虑使用Spring来组装我的应用程序的组件，但我有一个问题。我们的应用程序使用VM的全局配置存储库，并且与系统属性相似（但不完全相同）。

I'm considering using Spring to assemble the components of my application, but I've got a problem. Our application uses a configuration repository that is global to the VM, and is similar (but not precisely) to the system properties.

此配置API的访问方式如下： / p>

This configuration API is accessed like so:

Configuration.getDb ().get ("some_property_name")

有没有办法在Spring xml bean文件中使用这个全局配置中的值？ getDb 可能会根据配置库的当前状态（它有上下文）返回不同的值，但是我愿意声明Spring配置将完全在应用程序上下文初始化时加载。

Is there any way to use values from this global configuration in Spring xml bean files? getDb may return a different value depending on the current state of the configuration library (it has context), but I'm willing to make the statement that the Spring configuration will be fully-loaded at application context initialization time. Still, something more flexible would be fantastic.

由于我是Spring的新手，代码示例会让我的生活变得更加容易。

Given that I'm a Spring newbie, code examples would make my life a great deal easier.

推荐答案

要扩展cletus的suggesrion，我想说你想要一个自定义子类PropertyPlaceholderConfigurer，并重写resolvePlaceholder（）方法， Configuration.getDb（）代码。如果无法解析值，请委托回超类。

To expand on cletus' suggesrion, I'd say you want a custom subclass of PropertyPlaceholderConfigurer, and override the resolvePlaceholder() method, which would call your Configuration.getDb() code. If you can't resolve the value, then delegate back to the superclass.

例如：

public class MyPlaceholderConfigurer extends PropertyPlaceholderConfigurer {
    @Override
    protected String resolvePlaceholder(String placeholder, Properties props) {
        String value = Configuration.getDb().get(placeholder)
        if (value == null) {
            value = super.resolvePlaceholder(placeholder, props);
        }
        return value;
    }
}

然后在应用程序中定义一个类型为MyPlaceholderConfigurer的bean上下文和spring会自动咨询您的类以解析占位符值。

Then just define a bean of type MyPlaceholderConfigurer in your application context, and spring will automagically consult your class to resolve the placeholder values.

如果您的Configuration.getDb（）组件无法解析该值，超类允许spring查找值作为系统属性。或者，您可以将属性文件注入到bean中，也可以检查它。

If your Configuration.getDb() component can't resolve the value, then delegating back to the superclass allows spring to look up the value as a system property instead. Alternatively, you can inject a properties file into the bean, and it can check that also.

阅读参考文档的PropertyPlaceholderConfigurer的基本用法，怎么运行的。它非常灵活。

Read the ref docs on the basic usage of PropertyPlaceholderConfigurer, to get a feel for how it works. It's quite flexible.

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