Multi module Gradle project with IDE support

This article is a short how-to about multi-module project setup with usage of the Gradle automation build tool. Here’s how Rich Seller, a StackOverflow user, describes Gradle: Gradle promises to hit the sweet spot between Ant and Maven. It uses Ivy’s approach for dependency resolution. It allows for convention over configuration but also includes Ant tasks as first class citizens. It also wisely allows you to use existing Maven/Ivy repositories. So why would one use yet another JVM build tool such as Gradle? The answer is simple: to avoid frustration involved by Ant or Maven. Short story I was fooling around with some fresh proof of concept and needed a build tool. I’m pretty familiar with Maven so created project from an artifact, and opened the build file, pom.xml for further tuning. I had been using Grails with its own build system (similar to Gradle, btw) already for some time up then, so after quite a time without Maven, I looked on the pom.xml and found it to be really repulsive. Once again I felt clearly: XML is not for humans. After quick googling I found Gradle. It was still in beta (0.8 version) back then, but it’s configured with Groovy DSL and that’s what a human likes :) Where are we In the time Ant can be met but among IT guerrillas, Maven is still on top and couple of others like for example Ivy conquer for the best position, Gradle smoothly went into its mature age. It’s now available in 1.3 version, released at 20th of November 2012. I’m glad to recommend it to anyone looking for relief from XML configured tools, or for anyone just looking for simple, elastic and powerful build tool. Lets build I have already written about basic project structure so I skip this one, reminding only the basic project structure: <project root> │ ├── build.gradle └── src ├── main │ ├── java │ └── groovy │ └── test ├── java └── groovy Have I just referred myself for the 1st time? Achievement unlocked! ;) Gradle as most build tools is run from a command line with parameters. The main parameter for Gradle is a ‘task name’, for example we can run a command: gradle build. There is no ‘create project’ task, so the directory structure has to be created by hand. This isn’t a hassle though. Java and groovy sub-folders aren’t always mandatory. They depend on what compile plugin is used. Parent project Consider an example project ‘the-app’ of three modules, let say: database communication layer domain model and services layer web presentation layer Our project directory tree will look like: the-app │ ├── dao-layer │ └── src │ ├── domain-model │ └── src │ ├── web-frontend │ └── src │ ├── build.gradle └── settings.gradle the-app itself has no src sub-folder as its purpose is only to contain sub-projects and build configuration. If needed it could’ve been provided with own src though. To glue modules we need to fill settings.gradle file under the-app directory with a single line of content specifying module names: include 'dao-layer', 'domain-model', 'web-frontend' Now the gradle projects command can be executed to obtain such a result: :projects ------------------------------------------------------------ Root project ------------------------------------------------------------ Root project 'the-app' +--- Project ':dao-layer' +--- Project ':domain-model' \--- Project ':web-frontend' …so we know that Gradle noticed the modules. However gradle build command won’t run successful yet because build.gradle file is still empty. Sub project As in Maven we can create separate build config file per each module. Let say we starting from DAO layer. Thus we create a new file the-app/dao-layer/build.gradle with a line of basic build info (notice the new build.gradle was created under sub-project directory): apply plugin: 'java' This single line of config for any of modules is enough to execute gradle build command under the-app directory with following result: :dao-layer:compileJava :dao-layer:processResources UP-TO-DATE :dao-layer:classes :dao-layer:jar :dao-layer:assemble :dao-layer:compileTestJava UP-TO-DATE :dao-layer:processTestResources UP-TO-DATE :dao-layer:testClasses UP-TO-DATE :dao-layer:test :dao-layer:check :dao-layer:build BUILD SUCCESSFUL Total time: 3.256 secs To use Groovy plugin slightly more configuration is needed: apply plugin: 'groovy' repositories { mavenLocal() mavenCentral() } dependencies { groovy 'org.codehaus.groovy:groovy-all:2.0.5' } At lines 3 to 6 Maven repositories are set. At line 9 dependency with groovy library version is specified. Of course plugin as ‘java’, ‘groovy’ and many more can be mixed each other. If we have settings.gradle file and a build.gradle file for each module, there is no need for parent the-app/build.gradle file at all. Sure that’s true but we can go another, better way. One file to rule them all Instead of creating many build.gradle config files, one per each module, we can use only the parent’s one and make it a bit more juicy. So let us move the the-app/dao-layer/build.gradle a level up to the-app/build-gradle and fill it with new statements to achieve full project configuration: def langLevel = 1.7 allprojects { apply plugin: 'idea' group = 'com.tamashumi' version = '0.1' } subprojects { apply plugin: 'groovy' sourceCompatibility = langLevel targetCompatibility = langLevel repositories { mavenLocal() mavenCentral() } dependencies { groovy 'org.codehaus.groovy:groovy-all:2.0.5' testCompile 'org.spockframework:spock-core:0.7-groovy-2.0' } } project(':dao-layer') { dependencies { compile 'org.hibernate:hibernate-core:4.1.7.Final' } } project(':domain-model') { dependencies { compile project(':dao-layer') } } project(':web-frontend') { apply plugin: 'war' dependencies { compile project(':domain-model') compile 'org.springframework:spring-webmvc:3.1.2.RELEASE' } } idea { project { jdkName = langLevel languageLevel = langLevel } } At the beginning simple variable langLevel is declared. It’s worth knowing that we can use almost any Groovy code inside build.gradle file, statements like for example if conditions, for/while loops, closures, switch-case, etc… Quite an advantage over inflexible XML, isn’t it? Next the allProjects block. Any configuration placed in it will influence – what a surprise – all projects, so the parent itself and sub-projects (modules). Inside of the block we have the IDE (Intellij Idea) plugin applied which I wrote more about in previous article (look under “IDE Integration” heading). Enough to say that with this plugin applied here, command gradle idea will generate Idea’s project files with modules structure and dependencies. This works really well and plugins for other IDEs are available too. Remaining two lines at this block define group and version for the project, similar as this is done by Maven. After that subProjects block appears. It’s related to all modules but not the parent project. So here the Groovy language plugin is applied, as all modules are assumed to be written in Groovy. Below source and target language level are set. After that come references to standard Maven repositories. At the end of the block dependencies to groovy version and test library – Spock framework. Following blocks, project(‘:module-name’), are responsible for each module configuration. They may be omitted unless allProjects or subProjects configure what’s necessary for a specific module. In the example per module configuration goes as follow: Dao-layer module has dependency to an ORM library – Hibernate Domain-model module relies on dao-layer as a dependency. Keyword project is used here again for a reference to other module. Web-frontend applies ‘war’ plugin which build this module into java web archive. Besides it referes to domain-model module and also use Spring MVC framework dependency. At the end in idea block is basic info for IDE plugin. Those are parameters corresponding to the Idea’s project general settings visible on the following screen shot. jdkName should match the IDE’s SDK name otherwise it has to be set manually under IDE on each Idea’s project files (re)generation with gradle idea command. Is that it? In the matter of simplicity – yes. That’s enough to automate modular application build with custom configuration per module. Not a rocket science, huh? Think about Maven’s XML. It would take more effort to setup the same and still achieve less expressible configuration quite far from user-friendly. Check the online user guide for a lot of configuration possibilities or better download Gradle and see the sample projects. As a tasty bait take a look for this short choice of available plugins: java groovy scala cpp eclipse netbeans ida maven osgi war ear sonar project-report signing and more, 3rd party plugins…

This article is a short how-to about multi-module project setup with usage of the Gradle automation build tool.

Here’s how Rich Seller, a StackOverflow user, describes Gradle:

Gradle promises to hit the sweet spot between Ant and Maven. It uses Ivy’s approach for dependency resolution. It allows for convention over configuration but also includes Ant tasks as first class citizens. It also wisely allows you to use existing Maven/Ivy repositories.

So why would one use yet another JVM build tool such as Gradle? The answer is simple: to avoid frustration involved by Ant or Maven.

Short story

I was fooling around with some fresh proof of concept and needed a build tool. I’m pretty familiar with Maven so created project from an artifact, and opened the build file, pom.xml for further tuning.
I had been using Grails with its own build system (similar to Gradle, btw) already for some time up then, so after quite a time without Maven, I looked on the pom.xml and found it to be really repulsive.

Once again I felt clearly: XML is not for humans.

After quick googling I found Gradle. It was still in beta (0.8 version) back then, but it’s configured with Groovy DSL and that’s what a human likes :)

Where are we

In the time Ant can be met but among IT guerrillas, Maven is still on top and couple of others like for example Ivy conquer for the best position, Gradle smoothly went into its mature age. It’s now available in 1.3 version, released at 20th of November 2012. I’m glad to recommend it to anyone looking for relief from XML configured tools, or for anyone just looking for simple, elastic and powerful build tool.

Lets build

I have already written about basic project structure so I skip this one, reminding only the basic project structure:

<project root>
│
├── build.gradle
└── src
    ├── main
    │   ├── java
    │   └── groovy
    │
    └── test
        ├── java
        └── groovy

Have I just referred myself for the 1st time? Achievement unlocked! ;)

Gradle as most build tools is run from a command line with parameters. The main parameter for Gradle is a ‘task name’, for example we can run a command: gradle build.
There is no ‘create project’ task, so the directory structure has to be created by hand. This isn’t a hassle though.
Java and groovy sub-folders aren’t always mandatory. They depend on what compile plugin is used.

Parent project

Consider an example project ‘the-app’ of three modules, let say:

  1. database communication layer
  2. domain model and services layer
  3. web presentation layer

Our project directory tree will look like:

the-app
│
├── dao-layer
│   └── src
│
├── domain-model
│   └── src
│
├── web-frontend
│   └── src
│
├── build.gradle
└── settings.gradle

the-app itself has no src sub-folder as its purpose is only to contain sub-projects and build configuration. If needed it could’ve been provided with own src though.

To glue modules we need to fill settings.gradle file under the-app directory with a single line of content specifying module names:

include 'dao-layer', 'domain-model', 'web-frontend'

Now the gradle projects command can be executed to obtain such a result:

:projects
------------------------------------------------------------
Root project
------------------------------------------------------------
Root project 'the-app'
+--- Project ':dao-layer'
+--- Project ':domain-model'
\--- Project ':web-frontend'

…so we know that Gradle noticed the modules. However gradle build command won’t run successful yet because build.gradle file is still empty.

Sub project

As in Maven we can create separate build config file per each module. Let say we starting from DAO layer.
Thus we create a new file the-app/dao-layer/build.gradle with a line of basic build info (notice the new build.gradle was created under sub-project directory):

apply plugin: 'java'

This single line of config for any of modules is enough to execute gradle build command under the-app directory with following result:

:dao-layer:compileJava
:dao-layer:processResources UP-TO-DATE
:dao-layer:classes
:dao-layer:jar
:dao-layer:assemble
:dao-layer:compileTestJava UP-TO-DATE
:dao-layer:processTestResources UP-TO-DATE
:dao-layer:testClasses UP-TO-DATE
:dao-layer:test
:dao-layer:check
:dao-layer:build

BUILD SUCCESSFUL

Total time: 3.256 secs

To use Groovy plugin slightly more configuration is needed:

apply plugin: 'groovy'

repositories {
    mavenLocal()
    mavenCentral()
}

dependencies {
    groovy 'org.codehaus.groovy:groovy-all:2.0.5'
}

At lines 3 to 6 Maven repositories are set. At line 9 dependency with groovy library version is specified. Of course plugin as ‘java’, ‘groovy’ and many more can be mixed each other.

If we have settings.gradle file and a build.gradle file for each module, there is no need for parent the-app/build.gradle file at all. Sure that’s true but we can go another, better way.

One file to rule them all

Instead of creating many build.gradle config files, one per each module, we can use only the parent’s one and make it a bit more juicy. So let us move the the-app/dao-layer/build.gradle a level up to the-app/build-gradle and fill it with new statements to achieve full project configuration:

pipeline {
    agent any
    stages {
        stage('Unit Test') {
            steps {
                sh 'mvn clean test'
            }
        }
        stage('Deploy Standalone') {
            steps {
                sh 'mvn deploy -P standalone'
            }
        }
        stage('Deploy AnyPoint') {
            environment {
                ANYPOINT_CREDENTIALS = credentials('anypoint.credentials')
            }
            steps {
                sh 'mvn deploy -P arm -Darm.target.name=local-4.0.0-ee -Danypoint.username=${ANYPOINT_CREDENTIALS_USR}  -Danypoint.password=${ANYPOINT_CREDENTIALS_PSW}'
            }
        }
        stage('Deploy CloudHub') {
            environment {
                ANYPOINT_CREDENTIALS = credentials('anypoint.credentials')
            }
            steps {
                sh 'mvn deploy -P cloudhub -Dmule.version=4.0.0 -Danypoint.username=${ANYPOINT_CREDENTIALS_USR} -Danypoint.password=${ANYPOINT_CREDENTIALS_PSW}'
            }
        }
    }
}

At the beginning simple variable langLevel is declared. It’s worth knowing that we can use almost any Groovy code inside build.gradle file, statements like for example if conditions, for/while loops, closures, switch-case, etc… Quite an advantage over inflexible XML, isn’t it?

Next the allProjects block. Any configuration placed in it will influence – what a surprise – all projects, so the parent itself and sub-projects (modules). Inside of the block we have the IDE (Intellij Idea) plugin applied which I wrote more about in previous article (look under “IDE Integration” heading). Enough to say that with this plugin applied here, command gradle idea will generate Idea’s project files with modules structure and dependencies. This works really well and plugins for other IDEs are available too.
Remaining two lines at this block define group and version for the project, similar as this is done by Maven.

After that subProjects block appears. It’s related to all modules but not the parent project. So here the Groovy language plugin is applied, as all modules are assumed to be written in Groovy.
Below source and target language level are set.
After that come references to standard Maven repositories.
At the end of the block dependencies to groovy version and test library – Spock framework.

Following blocks, project(‘:module-name’), are responsible for each module configuration. They may be omitted unless allProjects or subProjects configure what’s necessary for a specific module. In the example per module configuration goes as follow:

  • Dao-layer module has dependency to an ORM library – Hibernate
  • Domain-model module relies on dao-layer as a dependency. Keyword project is used here again for a reference to other module.
  • Web-frontend applies ‘war’ plugin which build this module into java web archive. Besides it referes to domain-model module and also use Spring MVC framework dependency.

At the end in idea block is basic info for IDE plugin. Those are parameters corresponding to the Idea’s project general settings visible on the following screen shot.

jdkName should match the IDE’s SDK name otherwise it has to be set manually under IDE on each Idea’s project files (re)generation with gradle idea command.

Is that it?

In the matter of simplicity – yes. That’s enough to automate modular application build with custom configuration per module. Not a rocket science, huh? Think about Maven’s XML. It would take more effort to setup the same and still achieve less expressible configuration quite far from user-friendly.

Check the online user guide for a lot of configuration possibilities or better download Gradle and see the sample projects.
As a tasty bait take a look for this short choice of available plugins:

  • java
  • groovy
  • scala
  • cpp
  • eclipse
  • netbeans
  • ida
  • maven
  • osgi
  • war
  • ear
  • sonar
  • project-report
  • signing

and more, 3rd party plugins…

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Motivation

From time to time our sprints scope is changing. It is not a big deal because we are trying to be agile :-) but Jira's burndowchart in this situation draw a peek. Because in fact that chart shows scope changes not a real burndown. It means, that chart cannot break down an x-axis if we really do more than we were planned – it always stop on at most zero.

Also for better progress monitoring we've started to split our user stories to technical tasks and estimating them. Original burndowchart doesn't show points from technical tasks. I can find motivation of this – user story almost finished isn't finished at all until user can use it. But in the other hand, if we know which tasks is problematic we can do some teamwork to move it on.

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Tools

I've started with lift framework. In the World of Single Page Applications, this framework has more than simple interface for serving REST services. It comes with awesome Comet support. Comet is a replacement for WebSockets that run on all browsers. It supports long polling and transparent fallback to short polling if limit of client connections exceed. In backend you can handle pushes in CometActor. For further reading take a look at Roundtrip promises

But lift framework is also a kind of framework of frameworks. You can handle own abstraction of CometActors and push to client javascript that shorten up your way from server to client. So it was the trigger for author of lift-ng to make a lift with Angular integration that is build on top of lift. It provides AngularActors from which you can emit/broadcast events to scope of controller. NgModelBinders that synchronize your backend model with client scope in a few lines! I've used them to send project state (all sprints and thier details) to client and notify him about scrum board changes. My actor doing all of this hard work looks pretty small:

Lift-ng also provides factories for creating of Angular services. Services could respond with futures that are transformed to Angular promises in-fly. This is all what was need to serve sprint history:

And on the client side - use of service:


In my opinion this two frameworks gives a huge boost in developing of web applications. You have the power of strongly typing with Scala, you can design your domain on Actors and all of this with simplicity of node.js – lack of json trasforming boilerplate and dynamic application reload.

DDD + Event Sourcing

I've also tried a few fresh approaches to DDD. I've organize domain objects in actors. There are SprintActors with encapsulate sprint aggregate root. Task changes are stored as events which are computed as a difference between two boards states. When it should be provided a history of sprint, next board states are computed from initial state and sequence of events. So I realize that the best way to keep this kind of event sourcing approach tested is to make random tests. This is a test doing random changes at board, calculating events and checking if initial state + events is equals to previously created state:



First look

Screenshot of first version:


If you want to look at this closer, check the source code or download ready to run fatjar on github.During a last few evenings in my free time I've worked on mini-application called micro-burn. The idea of it appear from work with Agile Jira in our commercial project. This is a great tool for agile projects management. It has inline tasks edition, drag & drop board, reports and many more, but it also have a few drawbacks that turn down our team motivation.