从另一个属性的属性占位符位置 [英] property-placeholder location from another property

问题描述

我需要从一个我不知道的位置将一些属性加载到Spring上下文中，直到程序运行。

I need to load some properties into a Spring context from a location that I don't know until the program runs.

所以我认为如果我有一个没有位置的PropertyPlaceholderConfigurer，它将从系统中读入 my.location 属性，然后我可以在上下文中使用该位置：property-placeholder

So I thought that if I had a PropertyPlaceholderConfigurer with no locations it would read in my.location from the system properties and then I could use that location in a context:property-placeholder

喜欢这个

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"/>    
<context:property-placeholder location="${my.location}"/>

但这不起作用， location =classpath：$ {my.location}

保罗

推荐答案

这里的问题是你正在尝试使用属性占位符语法配置属性占位符:)这有点像鸡蛋和鸡蛋的情况 - spring无法解析你的 $ {my.location} 占位符，直到它配置了property-placeholder。

The problem here is that you're trying to configure a property place holder using property placeholder syntax :) It's a bit of a chicken-and-egg situation - spring can't resolve your ${my.location} placeholder until it's configured the property-placeholder.

这不太令人满意，但你可以通过使用更多来避免它显式语法：

This isn't satisfactory, but you could bodge it by using more explicit syntax:

<bean class="org.springframework.beans.factory.config.PropertyPlaceHolderConfigurer">
   <property name="location">
      <bean class="java.lang.System" factory-method="getenv">
         <constructor-arg value="my.location"/>
      </bean>
   </property>
</bean>

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