How to add Properties to an Application Context

Question

I have a Standalone Application, this application calculates a value (Property) and then starts a Spring Context. My question is how can I add that calculated property to th

Answer 1

In Spring 3.1 you can implement your own PropertySource, see: Spring 3.1 M1: Unified Property Management.

First, create your own PropertySource implementation:

private static class CustomPropertySource extends PropertySource {

    public CustomPropertySource() {super("custom");}

    @Override
    public String getProperty(String name) {
        if (name.equals("myCalculatedProperty")) {
            return magicFunction();  //you might cache it at will
        }
        return null;
    }
}

Now add this PropertySource before refreshing the application context:

AbstractApplicationContext appContext =
    new ClassPathXmlApplicationContext(
        new String[] {"applicationContext.xml"}, false
    );
appContext.getEnvironment().getPropertySources().addLast(
   new CustomPropertySource()
);
appContext.refresh();

From now on you can reference your new property in Spring:

Also works with annotations (remember to add ):

@Value("${myCalculatedProperty}")
private String magic;

@PostConstruct
public void init() {
    System.out.println("Magic: " + magic);
}