如何在java对象里访问Spring中已加载的property内容

Exposing the spring properties bean in java

To allow our Java classes to access the properties from the same object as spring, we’ll need to extend the PropertyPlaceholderConfigurer so that we can provide a more convenient method for retrieving the properties (there is no direct method of retrieving properties!).

We can extend the spring provided class to allow us to reuse spring’s property resolver in our Java classes:

01	public class PropertiesUtil extends PropertyPlaceholderConfigurer {

02	private static Map propertiesMap;

03

04

@Override

05	protected void processProperties(ConfigurableListableBeanFactory beanFactory,

06	Properties props) throws BeansException {

07	super .processProperties(beanFactory, props);

08

09	propertiesMap = new HashMap<String, String>();

10	for (Object key : props.keySet()) {

11	String keyStr = key.toString();

12	propertiesMap.put(keyStr, parseStringValue(props.getProperty(keyStr),

13	props, new HashSet()));

14

}

15

}

16

17	public static String getProperty(String name) {

18	return propertiesMap.get(name);

19

}

20

}

If we now update the applicationProperties bean to use the PropertiesUtil class, we can use the static getProperty method to access the resolved properties via the same object as the spring configuration bean.

Of course, we could run into problems if a class tries to use PropertiesUtil before the spring context has been initialised. For example if you’re registering ServletContextListeners in your web.xml before configuring spring, you’ll get a NullPointerException if one of those classes tries to use PropertiesUtil. For that reason I’ve had to declare the spring context before any context listeners.

view source print ?

01	< context-param >

02	< param-name >contextConfigLocation</ param-name >

03	< param-value >

04	/WEB-INF/applicationContext.xml

05	</ param-value >

06	</ context-param >

07

08	< listener >

09	< listener-class >org.springframework.web.context.ContextLoaderListener</ listener-class >

10	</ listener >

11

12	<!-- Other listeners -->

References

1. http://www.jdocs.com/spring/1.2.8/org/springframework/beans/factory/config/PropertyPlaceholderConfigurer.html
2. http://j2eecookbook.blogspot.com/2007/07/accessing-properties-loaded-via-spring.html