Wednesday, July 17, 2013

Spring 3.1 - Programmatic access to Properties managed by Property Placeholder

Spring follows Inversion Of Control approach, this means that we can simply inject particular property into POJO. But there are some cases, when you would like to access property given by name directly from your code - some might see it as anti-pattern - this is palpably true, but lets concentrate on how to do it.
The PropertiesAccessor below provides access to properties loaded by Property Placeholder and encapsulates container specific stuff. It also caches found properties because call on AbstractBeanFactory#resolveEmbeddedValue(String) is not cheap.
public class PropertiesAccessor {

    private final AbstractBeanFactory beanFactory;

    private final Map<String,String> cache = new ConcurrentHashMap<>();

    protected PropertiesAccessor(AbstractBeanFactory beanFactory) {
        this.beanFactory = beanFactory;

    public  String getProperty(String key) {
            return cache.get(key);

        String foundProp = null;
        try {
            foundProp = beanFactory.resolveEmbeddedValue("${" + key.trim() + "}");
        } catch (IllegalArgumentException ex) {
           // ok - property was not found

        return foundProp;