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[[tut-services-step3,Step 3 - Reading the Service Configuration]]
= Step 3 - Reading the Service Configuration =

Services typically have configuration. Configurations are directly supported in Polygene™. A
ConfigurationComposite is a subtype of EntityComposite. That is because
configurations are stored in EntityStores, can be modified in runtime by client code and has
the same semantics as regular entities.

Polygene™ also handles the bootstrapping of configuration for the services. If the ConfigurationComposite is
not found in the configured entity store, then Polygene™ will automatically locate a properties file for each
service instance, read those properties into a ConfigurationComposite instance, save that to the
entity store and provide the values to the service. The properties file must be with the same name as
the service instance with the extension "properties" in the same package as the service.

For this exercise, create a LibraryConfiguration that contains "titles", "authors" and "copies".
The first two are a string with a comma separated list, and the "copies" is just an Integer with how many
copies are made of each title.

Steps to do.

- Create a LibraryConfiguration interface that extends ConfigurationComposite, and has three Property instances named "titles", "authors" and "copies", where the first two are of String type and the last is of Integer type.
- Delete the LibraryActivator and remove the @Activators annotation from the LibraryService and the corresponding createInitialData method.
- In the LibraryMixin remove the member injection of the ValueBuilderFactory, and instead inject the ValueBuilderFactory in the constructor.
- Inject the LibraryConfiguration via the constructor. The injection scope is @This.
- Create a resource called LibraryService.properties and place it in the directory +org/apache/polygene/tutorials/services/step4+ in the classpath (for instance, src/main/resources ). Put something like this in:
    titles=Domain Driven Design, Pragmatic Programmer, Extreme Programming Explained
    authors=Eric Evans, Andy Hunt, Kent Beck
    #Number of copies of each book.
    copies=3
- Load initial data from the LibraryConfiguration in the LibraryMixin constructor.