如何在Spring2.5.1中获取@Configuration注释功能

Question

我需要在加载上下文时加载属性文件。（constants.properties如下例所示）此属性文件中的一个键指向另一个不在类路径中的属性文件（例如privatedata.properties） 。我需要读取privatedata.properties文件的属性并注入我的bean。我可以在Spring 3.x中借助@Configuration注释在下面执行此操作。我如何在Spring2.5.1中获得相同的功能？

使用Spring 3.x

package com.snippets.enterprise;

**@Configuration**

@PropertySource("classpath:/constants.properties")

public class SpringConfig {    }

<context:component-scan base-package="com.snippets.enterprise"/>
 //constants.properties has a key called private.supportiveFile and that points to the   
 file in **non-class path**

 <context:property-placeholder location="file:${private.supportiveFile}" /> 

    <bean id="helloWorldBean"
    class="com.snippets.enterprise.services.HelloWorld">
     <property name="key" value="${keypath}" />
    </bean>

How can I get the same capability in Spring2.5.X. 

org.springframework.context.annotation.Configuration is present from spring3.x onwards.