Grails Firebase Plugin

Firebase is an API to store and sync data in realtime.

When data changes, apps built with Firebase update instantly across every device including web and mobile. Firebase-powered apps work offline. Data is synchronized instantly when app regains connectivity.

Data Structure in firebase is designed to be represented by a specific URL and the client can register a listener/callback to accomplish an event when a particular element has changed/added/removed. This plugin is a grails wrapper over the Firebase Java client to accomplish the callback functionalitly on modification of data.

Firebase is not only targeted for client apps but also for servers. This blog shows where in a technology stack firebase fits in.

Installation

plugins {
    compile ':firebase:0.0.1'
}

Usage

This plugin registers a bean firebaseRef which extends Firebase and implements methods in a Groovier way.

Steps:

1. Sign up in Firebase.com to create a Firebase Data Structure.
2. Use the data structure id abcd-fire-7000 from the URL for example (https://abcd-fire-7000.firebaseio.com) in the below config setting in Config.groovy
3. Add the secretKey provided by Firebase in order to generate a token which will be used for authentication. Custom Authentication is used for this plugin.

Example:

grails {
    plugin {
        firebase {
            base = "abcd-fire-7000"
            secretKey = "a5b8c5d8e9f3g7h1i1j0k5l2m2n4o8p4q4r8s7t6u9v7w8x8y8z5"
        }
    }
}

To use firebase inject firebaseRef in any of the grails artifact:

//Service class
def firebaseRef

def addValue(){
    firebaseRef.child("first").value = "John"
    firebaseRef.child("last").value = "Doe"

    // Value Event Listener
    // Closure callback takes two parameters
    // 1. The value that was change (null in case of error)
    // 2. Errors if any during update (null in case of success)
    firebaseRef.on('value'){ data, error ->
        println "first name is ${data.value}"
    }
}

def method() {

    // Writing data as a child
    firebaseRef.value  = [
        address: [
            street: '123 Main Street',
            apt: 123,
            city: 'Columbus',
            zip: 43230,
            state: 'OH',
            country: 'USA'
        ]
    ]
    
    // Child Event Listener for add event
    // Closure callback takes three parameters
    // 1. Map representation of the child that was added (null in case of error)
    // 2. Previous name of child (null in case of addition)
    // 2. Errors if any during update (null in case of success)
    firebaseRef.onChildAdded { data, previous, error ->
        println "Add callback"
        println data
        println previous
        println error
    }

    // Child Event Listener for change event
    // Closure callback takes three parameters
    // 1. Map representation of the child that was changed (null in case of error)
    // 2. Previous name of child (null in case of addition)
    // 2. Errors if any during update (null in case of success)
    firebaseRef.on('childChanged'){ data, previous, error ->
        println "Change callback"
        println data
        println previous
        println error
    }

    // Child Event Listener for remove event
    // Closure callback takes three parameters
    // 1. Map representation of the child that was removed (null in case of error)
    // 2. Previous name of child (null in case of addition)
    // 2. Errors if any during update (null in case of success)
    firebaseRef.on('childRemoved'){ data, previous, error ->
        println "Remove callback"
        println data
        println previous
        println error
    }
    
    //Additional ways to use for Child Events
    firebaseRef.onChildChanged{ }
    firebaseRef.onChildRemoved{ }
    
    //Additional ways to used for Value Event
    firebaseRef.onValue { }
    
    //Listener for single value event (only applicable for value)
    firebaseRef.once { }
}

TODO

• Add transactional feature
• Add authentication
• Add offline/online mode
• Add GORM features

License

APACHE 2.0