JarCastingcommons-configuration
This provides a Spring scanned configuration file to support the @ConfigKey annotation from Sticky Code that injects System properties into your Spring objects.
e.g.
@UniversityComponent
class MyClass {
@ConfigKey("person.name") String name
@ConfigKey("person.age") Integer age
@ConfigKey Boolean alive // myclass.alive
@ConfigKey List<String> aliases // myclass.aliases
@ConfigKey Map<String, Integer> childrenAges // myclass.childrenAges
}
in system properties you would have
person.name=fred
person.age=35
myClass.alive=true
myClass.aliases=The Hammer, Sooty, Sweep
myClass.childrenAges=Barbara:7, William:2
You can include in your class a @PostConfigured annotation to then do post processing on the configuration.
@UniversityComponent
class AlsoMyClass {
@ConfigKey String parts = "gibberish"
@ConfigKey String password
@PostConfigured
public void configure() {
// do something here
}
}
Configuration Sources
There are two - the Jar Manifest file is first, the System Properties are second. Jar Manifest's can't use keys with a "." in their name, so those are immediately skipped.
Alternatives
We can use the @Value annotation from Spring, but this has a number of "issues":
- @Value annotated fields in base classes will not pull their configuration settings when the bean is configured
- @Value requires you to specify where your properties are coming from, which generally is undesirable as the source of configuration is extensible.
- @Value's default mechanism is clumsy, requiring error prone stringization of defaults
Web Usage
The artifact includes a web fragment, if included in a Servlet 3.x container, it will automatically be added to the global web.xml
Other Spring usage
Anyone using the Artifact outside of a web container will need to get the StickyBootstrap object and call "start" on it (see the StickyBootStrapServlet for an example).
Notes
- if you don't give a default value and the user doesnt provide a value, the initialization of your application will immediately fail (FAST FAIL)
Applications using: pretty much everything
