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This is the Alexa skills Plugin!

This plugin helps you create Speechlets/Skills on Grails. It will create a starter class for you so you can get running quickly making your own skills.


add the following to the dependencies {} block to your build.gradle:

dependencies {
     compile "org.grails.plugins:alexa-skills:0.1.2"

also if you have issues resolving the plugin, try adding my bintray repo (NOT to buildscript block but the lower one):

repositories {
    maven { url  "" }
    maven {
            url  "" 

How it works

run 'grails create-speechlet ' This will create a speechlet class file located in grails-app/speechlets. Do not use the suffix 'Speechlet' because that will be automatically appended to the name.


Here's the config values you can set in application.yml or application.groovy:

alexaSkills.supportedApplicationIds (String)

  • this is a comma delimited list of application Ids you speechlet will recognize.
  • you can get ID this under Skills->create on

alexaSkills.disableVerificationCheck (boolean)

  • if you are debugging and sending in canned request (see 'serializeRequests') via CURL turn this on
  • be very careful not to disable this in a public service as it turns off all checking the request is really coming from Amazon.

alexaSkills.serializeRequests (boolean)

  • if you are having problems wondering what is going on with your skill or want to capture a request and replay it in CURL it will write them to disk

alexaSkills.serializeRequestsOutputPath (boolean)

  • if you turn on serialization requests this is the path the files will be saved to. The files will be names in the format:
  • files will be saved in the format speechlet-${System.currentTimeMillis()}.out

Recommended usage with a Controller

class TestController {

    def speechletService
    def testSpeechlet

    def index() {
        speechletService.doSpeechlet(request,response, testSpeechlet)


Here you see the speechlet is turned into a Spring bean, and you invoke the speechlet service and pass it in. Likely we could turn the speechlet artefact class into a controller itself in the future to skip this. If you are using Spring security, make sure to whitelist the urlmapping for the index.

Blog Article from Grails Team Blog on how to make this all work


Recently I gave a talk at about building applications for the Amazon Alexa platform. I talked about using Groovy with Lambdas to demonstrate Skills (Alexa Apps) as well as using Grails. I'll give this talk again at at the end of July and have even more good stuff to show. On top of that, after working on this for months I have the material to have an Alexa workshop at to Collin Harrington for helping with the idea). Good Times! I wanted to write a post as a step-by step on using a plugin I've recently developed as to help you crank out Alexa apps(skills or speechlets). Amazon has a promotion right now, if you submit a new skill to their library, you can win a free T-Shirt, so maybe you can make something cool with this and get one! You do not even need an Amazon device: you can point your browser to to use their emulator.

Let me first get started to explain how these things work and a little about the devices. Starting a couple years ago, Amazon released a home device/speaker thing called the Echo. It's a household helper device with very nice multi-directional microphones, and a nice speaker for playing music. At first I didn't get one or understand it: it sounded like a useless toy to me. However peers gobbled them up and started playing around with them. They weren't building apps for it, but raved about how cool it was and how it helped automate their home and do useful things. Then they started saying they loved it so much they were buying more units and putting them all over their house. Now my attention was had - of course the first thing that pops into my head was 'how can I get Groovy to work with this thing?'

The first examples they give are all about AWS Lambda functions in Node - however they aren't fantastic on Java because they have a hard limit of 50mb jars you can upload. Surely you can't fit all of grails and dependencies in there to do much. Still we gave it a shot - I followed Benoit Hédiard's presentation on Groovy with Lambdas from GGX 2015. I sat down with a buddy of mine, Lee Fox (He will be at, and we hammed out a bunch of ideas we could build with it - in Groovy of course!

The first app we got working was a simple Twitter app that combined Groovy, Spring Social and Skills to make a skill that would connect to Twitter and search for tweets, as well as give updates to your timeline. You can find the code here. Good! Now we're getting somewhere. I did a little digging and found they have some servlet support to make a stand along web service - now we can get Grails involved and make this less hideous.

Next we took it a level up - we didn't want the user to have to hard-code their twitter API keys to run the app, and you can't publish a skill that pulls down someone else's twitter info. So we build a Grails app that used Spring Security, Oath plugin, and Spring Security UI to allow a UI that lets you register and enter your own twitter keys for your account. Source for that is here.

After that it was time to make a plugin to help you make these skills - that I published while I was out at here. It works similar to the Quartz plugin in that you have a CLI command to create a working template of a Skill to get you started. I will show you here how to build a skill using the Grails plugin to get you started making your own Skills in a short about of time.

How Alexa service Works

The devices themselves, (which are currently the Echo, Tap, Dot, and FireTV) don't do a whole lot. They even publish the source to the devices for you to look at if you choose here. The magic resides on the amazon side that handles all the voice recognition and handling of requests. Basically what happens is the user initiates a action (skill) on the device, and it goes to the alexa service to figure out what you want to do. When your app is invoked, it calls back to your app via a JSON HTTPS call and initiates a series of Intents to make your app do things. Your app simple waits for the call and takes appropriate action (via JSON) to do what you want. It's up to you as the developer to make it do something useful.

The picture above give you an idea of how it works (from Amazon's site). Let's go over Intents and Sample utterances to have a better idea of what's going on.


Intents are sort of like simplified Intents on android if you have every done Android coding. They signal an intention for a command to run to do something.

Let's look at an example one to get an idea:

  "intents": [
      "intent": "ResponseIntent",
      "slots": [
          "name": "Answer",
          "type": "AMAZON.LITERAL"
      "intent": "QuestionCountIntent",
      "slots": [
          "name": "Count",
          "type": "AMAZON.NUMBER"
      "intent": "AMAZON.HelpIntent"

Here this application can trigger 3 intents: ResponseIntent, QuestionCountIntent, and HelpIntent. You use JSON to tell it what these are. You can define 'slots' which is the expected responses which are comprised of a name and Type. There are pre-defined data types you can use to help amazon parse what is said (Number for example knows the user is going to say a number. Literal is a simple String. Some intents don't need anything as they are 'built in' like the help intent (no inputs).

A little bit about slots - they are entirely optional. You can do things like define a list of allowed responses (custom slots) that are valid things for the user to say. In this case the ResponseIntent is free form, and we sort out what we want to do by parsing the string we get from Amazon (translated via TTS).

Sample Utterances

Let's look at another example:

ResponseIntent {test|Answer}
ResponseIntent {last player|Answer}
ResponseIntent {test test|Answer}
ResponseIntent {test test test|Answer}
ResponseIntent {test test test test|Answer}
QuestionCountIntent {Count} questions

Here we see the intent each utterances (what the person says) and map it to an intent. Amazon will generate common words like conjunctions and ignored things on their end so you don't have to mess with handling things like 'and', 'the', 'or' etc. Variables are surrounded by {}. You can use the | operator to specify alternate options. If you want to say something to your skill, it must match the pattern here. For this case, we want to parse multi-world answers to a question. Basically here we support one, two, three of four word responses - anything else will be cut off/ignored. The last item allows the user to answer how many questions they want to be asked.


  • A publicly available container(Self running Grails jar, Tomcat, Elastic Beanstalk, etc) to launch your app with HTTPS on port 443 (no way around this). Can be self-signed for DEV mode only.
  • If you want to use audio snippets via SSML they must be hosted as above but with a recognized CA (no self-signed). S3 Static HTTPS buckets are easiest.
  • SSL Certificate common name MUST match hostname (even for self-signed DEV certs)

Let's make a Grails app using the plugin and I will explain more as we go

The plugin is for Grails 3.x only. Let's create a new app first:

grails create-app skillsTest

Now lets open build.gradle and add the plugin into the dependencies {} closure:

compile "org.grails.plugins:alexa-skills:0.1.1"

Now let's create a skill from the command line:

grails create-speechlet SkillsTest
| Rendered template Speechlet.groovy to destination grails-app/speechlets/skillstest/SkillsTestSpeechlet.groovy

Now let's see what it's created in grails-app/speechlets:

class SkillsTestSpeechlet implements GrailsConfigurationAware, Speechlet {

    def grailsApplication

    Config grailsConfig
    def speechletService

    def index() {
        speechletService.doSpeechlet(request,response, this)

     * This is called when the session is started
     * Add an initialization setup for the session here
     * @param request SessionStartedRequest
     * @param session Session
     * @throws SpeechletException
    public void onSessionStarted(final SessionStartedRequest request, final Session session)
            throws SpeechletException {"onSessionStarted requestId={}, sessionId={}", request.getRequestId(),


     * This is called when the skill/speechlet is launched on Alexa
     * @param request LaunchRequest
     * @param session Session
     * @return
     * @throws SpeechletException
    public SpeechletResponse onLaunch(final LaunchRequest request, final Session session)
            throws SpeechletException {"onLaunch requestId={}, sessionId={}", request.getRequestId(),

        return getWelcomeResponse()

     * This is the method fired when an intent is called
     * @param request IntentRequest intent called from Alexa
     * @param session Session
     * @return SpeechletResponse tell or ask type
     * @throws SpeechletException
    public SpeechletResponse onIntent(final IntentRequest request, final Session session)
            throws SpeechletException {"onIntent requestId={}, sessionId={}", request.getRequestId(),

        log.debug("invoking intent:${intentName}")
        PlainTextOutputSpeech speech = new PlainTextOutputSpeech()
        // Create the Simple card content.
        SimpleCard card = new SimpleCard(title:"Twitter Search Results")
        def speechText = "I will say something"
        def cardText = "I will print something"
        // Create the plain text output.
        SpeechletResponse.newTellResponse(speech, card)

     * Grails config is injected here for configuration of your speechlet
     * @param co Config
    void setConfiguration(Config co) {
        this.grailsConfig = co

     * this is where you do session cleanup
     * @param request SessionEndedRequest
     * @param session
     * @throws SpeechletException
    public void onSessionEnded(final SessionEndedRequest request, final Session session)
            throws SpeechletException {"onSessionEnded requestId={}, sessionId={}", request.getRequestId(),
        // any cleanup logic goes here

    SpeechletResponse getWelcomeResponse()  {
        String speechText = "Say something when the skill starts"

        // Create the Simple card content.
        SimpleCard card = new SimpleCard(title: "YourWelcomeCardTitle", content: speechText)

        // Create the plain text output.
        PlainTextOutputSpeech speech = new PlainTextOutputSpeech(text:speechText)

        // Create reprompt
        Reprompt reprompt = new Reprompt(outputSpeech: speech)

        SpeechletResponse.newAskResponse(speech, reprompt, card)

     * default responder when a help intent is launched on how to use your speechlet
     * @return
    SpeechletResponse getHelpResponse() {
        String speechText = "Say something when the skill need help"
        // Create the Simple card content.
        SimpleCard card = new SimpleCard(title:"YourHelpCardTitle",
        // Create the plain text output.
        PlainTextOutputSpeech speech = new PlainTextOutputSpeech(text:speechText)
        // Create reprompt
        Reprompt reprompt = new Reprompt(outputSpeech: speech)
        SpeechletResponse.newAskResponse(speech, reprompt, card)

     * if you are using account linking, this is used to send a card with a link to your app to get started
     * @param session
     * @return
    SpeechletResponse createLinkCard(Session session) {

        String speechText = "Please use the alexa app to link account."
        // Create the Simple card content.
        LinkAccountCard card = new LinkAccountCard()
        // Create the plain text output.
        PlainTextOutputSpeech speech = new PlainTextOutputSpeech(text:speechText)
        log.debug("Session ID=${session.sessionId}")
        // Create reprompt
        Reprompt reprompt = new Reprompt(outputSpeech: speech)
        SpeechletResponse.newTellResponse(speech, card)


Also the plugin will generate a Controller class embedded in your Speechlet file. If you are using Spring Security, you will want to make sure that uri is assessable to the outside to the Alexa service can contact it (there are some requirements I'll fill you in on later):

 * this controller handles incoming requests - be sure to white list it with SpringSecurity
 * or whatever you are using
class SkillsTestController {

    def speechletService
    def skillsTestSpeechlet

    def index() {
        speechletService.doSpeechlet(request,response, skillsTestSpeechlet)


The speechlet artefact will be registered as a Spring bean so it's automatically injected. There is also a service the plugin provides to handle the boring stuff like verifying the request, checking the app ID (more on that later) and the plumbing that calls your skill.

Built-in Events

Looking at the code example above, you can see it made several methods for you. These are part of the skill(speechlet) lifecycle. The first one is:


This allows you to store variables for the duration of the session (the interactions as a whole of the app for that time). You can do some setup here and store variables you can use later. This is technically optional for you to implement.


This is called when you invoke the skill. When you say 'Alexa open skillTest' etc this is you chance to say an opening message about your app, what it does, or what they will need to do.


This is the meat and is required to be implemented. When your sample utterances maps to an Intent when the user says something this is invoked. Here you should generate a card that will appear in the Alexa app on your phone (you can also get to this on your local network via browser by going to ''. Cards are similar to Android cards (more popular in Android Wear) that simply show a message to the user they can see what is going on. You can make several kinds of cards which are Simple, Standard, and LinkAccount. Here we have a switch statement to figure out what Intent to process and call the code for the appropriate intent.


This is the last one, optional, where you can clean up and session resources you might have created like database records for the run.

I've added a few other helper methods to see how to render a help response, link an account, and get some setup details from the Grails config. As a first pass, just try to get the default template working, then start to change things like changing the text, add an Intent, etc.

Set up your app on Amazon Developer Portal

This is separate from AWS. I am not aware of any APIs that will create all of this for you so you have to sign up for an account and do this by hand for each skill you want to run.

  • Pull down the 'twitterAuth' app here to get some Intents/Sample utterances to try. They are located in src/main/resources.

  • Sign up for the Amazon developer program here if you haven't already

  • Click on Apps and Services -> Alexa

  • Click on Alexa Skill Kit / Get Started -> Add New Skill

  • Pick any name and any invocation name you want to start the app on your Echo / Alexa Device

  • Copy the contents of src/main/resources/IntentSchema.json into Intent Schema.

  • Don't fill in anything for slots

  • Under Sample Utterances, copy the contents of the file src/main/resources/SampleUtterances.txt

  • Under configuration Copy the url for /twitterAuth/twitter/index for the endpoint for your server (Choose amazon https not ARN). Click next

  • Leave 'enable account linking' turned off.

  • For domain list, enter a domain that matches your SSL cert the oauth tokens will be valid for. You may use a self-signed cert for development mode, but if you want to publish your skill, your server will need to be running a real recognized certificate (a cheap option is RapidSSL).

  • Enter the url for the privacy policy on your server. It can be any valid web page, a link will show during account linking in the alexa app

  • Hit Save

  • Click on SSL Certificate. If you have a self-signed cert (will only work for DEV mode) paste it here under 'I will upload a self-signed certificate in X.509 format.'

  • Hit Save and go to Test page and hit Save

  • Go to Privacy and Compliance, and fill out the info there (It's required)

Now note the application ID it gives you. You will need to add this to the application.groovy/yml file so the application will know the app ID and accept it.

Copy the application ID on the first tab 'SKILL INFORMATION', and paste that into application.groovy

alexaSkills.disableVerificationCheck = true // helpful for debugging or replay a command via curl
alexaSkills.serializeRequests = true // this logs the requests to disk to help you debug
alexaSkills.serializeRequestsOutputPath = "/tmp/"

Build and deploy your war file to your server (btw it must be port 443 HTTPS, no exceptions)

Test your app

Now try it on your Echo/Alexa device. Say either 'start' or 'open' and the invocation name you gave the app and follow the prompts! You can also use the test function on the portal itself.


Debugging can be very frustrating. Make sure to turn your log level to debug. In the Grails config, the there is an option called 'serializeRequests' and a output path for them. This allows you to capture the request that came from Amazon. If you are trying to test a fix for a bug, you can replay this via CURL. The files will look like this:

-rw-r--r-- 1 tomcat tomcat      598 Jun  6 22:45 speechlet-1465249551692.out
-rw-r--r-- 1 tomcat tomcat      636 Jun  6 22:45 speechlet-1465249557538.out
-rw-r--r-- 1 tomcat tomcat      598 Jun  6 22:46 speechlet-1465249601675.out
-rw-r--r-- 1 tomcat tomcat      636 Jun  6 22:46 speechlet-1465249607216.out

The build-in security provided by the plugin and underlying library will now allow you to reuse a request because the hash ahd timestamps are too old (to prevent this type of attack called a 'replay attack'). You can disable this check for dev purposes with the 'disableVerificationCheck' Grails config value. Now you can replay a file via CURL back to your server to avoid the whole voice interaction to test that one case (and test it locally!):

curl -vX POST http://localhost:8080/test/index -d @speechlet-14641464378122470.out --header "Content-Type: application/json"

If you save enough requests of a normal interaction, you could write some functional tests that replay this as part of a test suite or just be able to dev against them locally a bit.

Advanced stuff - full UI with Spring Security, OAuth

If your want a UI for the user and use account linking, an easy path is to add Spring Security, Spring Security UI, Spring Security OAuth grails plugins. You can see an example of how to do this here.

Advanced stuff - say sample audio clips in your skill

There is a supported markup called SSML which allows up to 90 seconds of low quality mp3 sound clips to play. Their settings/requirements are quick picky to work:

  • Must be hosted on a recognized CA HTTPS port 443 server (I use S3 static website for this)
  • Must be 16khz, 48 kb/s MP3 files
  • Use the open source tool 'ffmpeg' to encode them - these settings work: 'ffmpeg -y -i -ar 16000 -ab 48k -codec:a libmp3lame -ac 1 file.mp3'
  • See the heroQuiz app for an example of playback sounds being used.

Example SSML:

      <audio src="\"\"/"> ${speechText}

Useful links


The Alexa service is a great invention that is catching on. Google and Apple are dipping their toes into the market. I see the star trek experience in the home being a reality for everyone in a few years. Already my wife uses it (who swore she never would), and my 4 year old asks it to tell her jokes all the time. I use it to control my lights very often. The sky is the limit, and these tools can be useful in the workplace too. Get out there and build some neat stuff for Alexa with Grails!


This plugin helps you build alexa skills with Grails 3.x







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