Description

Russian documentation is available here

This plugin simplifies process of using config value in your Spring beans (controllers, services, taglibs and etc.). Let's check how you can use config value now:

import javax.annotation.PostConstruct

class MyService {

    def grailsApplication

    private myVariable

    @PostConstruct
    private setUp() {
        myVariable = grailsApplication.config.app.myVariable
    }

    void doSomeCoolStuff() {
        println myVariable
    }

}

I think this is not the best approach - why do you need to inject grailsApplication bean only to read config value? Let's improve this code:

import grails.util.Holders

import javax.annotation.PostConstruct

class MyService {

    private myVariable

    @PostConstruct
    private setUp() {
        myVariable = Holders.config.app.myVariable
    }

    void doSomeCoolStuff() {
        println myVariable
    }

}

Much better. But we can make it even shorter.

How can I use Grails Config Annotation to inject config value?

Here is similar problem solved with Grails Config Annotation:

import ru.grails.config.GrailsConfig

class MyService {

    @GrailsConfig("app.myVariable")
    private myVariable

    void doSomeCoolStuff() {
        println myVariable
    }

}

All you have to do is:

1. Import annotation: import ru.grails.config.GrailsConfig
2. Add @GrailsConfig annotation to the variable. Annotation value should be the same as variable name from Config.groovy file (in our case app.myVariable): @GrailsConfig("app.myVariable").

Default values

You can specify default variable value. When Config.groovy file doesn't have required variable default value will be used to configure variable. To configure default value use the following annotation value structure: config_variable_name_to_inject:default value. For example:

import ru.grails.config.GrailsConfig

class MyService {

    @GrailsConfig("app.myVariable:my default value")
    private myVariable

    void doSomeCoolStuff() {
        println myVariable
    }

}

When file Config.groovy doesn't have variable app.myVariable, then default value my default value will be used to configure variable myVariable.

Default values defined by class

If @GrailsConfig annotation doesn't specify default value then value defined by class will be used as default. For example:

import ru.grails.config.GrailsConfig

class MyService {

    @GrailsConfig("app.myDelay")
    private Long myDelay = 5000

    void doSomeCoolStuff() {
        sleep(myDelay)
    }

}

When file Config.groovy doesn't have variable app.myDelay, then class value 5000 will be used to configure variable myDelay.

Types casting

You can explicitly specify the variable type. Then variable value will be type casted to required type. For example:

import ru.grails.config.GrailsConfig

class MyService {

    @GrailsConfig("app.myVariable:-1")
    private Integer myVariable

    void doSomeCoolStuff() {
        println myVariable
    }

}

In this case value of config variable app.myVariable or default value -1 will be type casted to Integer type.

Code reloading

This plugin supports development with enabled code reloading (grails run-app) - variable values should be updated as you expect it. Variable value should be updated in the following cases:

• When you add/remove annotated variable
• When you change config variable value in Config.groovy
• When you change value of @GrailsConfig annotation

@GrailsConfig and Grails Controllers

Don't use @GrailsConfig with Grails Controllers! By default Grails Controllers have prototype scope. As documentation says A new controller will be created for each request. It means that @GrailsConfig annotation will spend more resources injecting config value for each request. You've got two ways to solve this problem:

1. Change controller's scope to singleton
2. Move @GrailsConfig annotation into service.

If you have any problems

If you have any problems or suggestions pls feel free to ask me - I'll be glad to answer you.

In conclusion

Pls note that @GrailsConfig only works in Spring beans (controller, services, tagLib's and etc.). Don't use it with POJO/POGO.