Overview of using Gradle for building Java EE applications. Presentation given at the NY Java SIG.

1. Faster Java EE Builds
with Gradle
RYAN CUPRAK

2. About
 Ryan Cuprak
 @ctjava
 rcuprak@gmail.com
 http://www.cuprak.info
 https://www.linkedin.com/in/rcuprak

3. Introducing Gradle
• Open source build automation system
• Apache 2.0 License
• Builds upon Apache Ant and Maven
• First released in 2007
• Uses a Groovy-based DSL (not XML)
• Uses directed acyclic graph to determine build order
• Supports multiple languages: Java, C++, C, etc.
• Rich plug-in architecture
• Convention over configuration but easily
customized/adapted

4. Introducing Gradle
• Build file can be versioned like dependencies.
Ever run Ant 1.9 file with Ant 1.6?
• Background daemon reduces build-time
• Supports incremental builds
• Built-in profiling support
• Build projects in parallel and some tasks*
• Built-in Ant/Maven integration
• Supported central repositories:
• Maven Central
• Jcenter
• Ivy

5. Build System Evolution
Ant
Maven
Gradle2004
2007
2000

6. Gradle versus Maven
Feature Gradle Maven
Fully configurable DAG ✅ ❌
Task Exclusion ✅ ❌
Dry Run ✅ ❌
Advanced Task Ordering ✅ ❌
Custom Distributions ✅ ❌
Checksum Based Cache ✅ ❌
Version Conflict Resolution ✅ ❌
File Based Dependencies ✅ ❌
Finalizers ✅ ❌
Custom Dependency Scopes ✅ ❌
ReplaceByRules ✅ ❌
https://gradle.org/maven-vs-gradle

7. Why Gradle?

8. Questions
1. Do you need to learn Groovy?
No (Good idea)
2. Do you need to completely refactor your code base?
No
3. Do you need additional IDE plugins?
Maybe
4. Do you need to change your build process?
Depends
5. Do you need to port your entire build system over?
No – can port over individual modules
6. Can you embed custom Ant logic?
Yes

9. Questions…
7. Must all dependencies originate from a repository?
No
8. Can artifacts be pushed to a repository?
Yes
9. Can Jenkins initiate Gradle builds?
Yes

10. Why Gradle for Java EE?
Java EE projects are:
 Large
 Complex
 Contain many dependencies
 Ant lacks dependency management
Large Ant files are a nightmare to debug
Maven isn’t flexible
 Custom plugins aren’t the solution
 Evolving slowly

11. Installation
 Installation similar to Ant/Maven
 Download and install from gradle.org
 Set environment variables:
 GRADLE_HOME
 PATH (to GRADLE_HOME/bin)
 gradle = ant = mvn

12. Key Gradle Files
Build file build.gradle
Configuration settings settings.gradle
Local settings ~/.gradle/gradle.properties
Local repository (project)/.gradle
build.gradle = pom.xml = build.xml

13. Gradle Daemon
Gradle daemon is enabled by default
(Disable for continuous build environments!)
Displaying status
gradle –status
Stopping daemon:
gradle –stop
Disabling daemon:
Add org.gradle.daemon=false to ~/.gradle

14. Project Creation
To start a new project:
 gradle init – creates a new project
 Uses pom.xml if present.
 Imports multi-model projects
 Optionally specify –type <type>
 java-library
 scala-library
 groovy-library
 basic (default) – no src directories created.
 Central repository defaults to jcenter()
https://bintray.com/bintray/jcenter

15. Project Creation…
 gradle init --type java-library
Default Project Layout
src
main
resources
test
java
resources
build.gradle
settings.gradle
java
project

16. Initial Gradle File

17. Command line – listing tasks
gradle –q tasks
------------------------------------------------------------
All tasks runnable from root project
------------------------------------------------------------
Build tasks
-----------
assemble - Assembles the outputs of this project.
build - Assembles and tests this project.
buildDependents - Assembles and tests this project and all
projects that depend on it.
buildNeeded - Assembles and tests this project and all projects
it depends on.
classes - Assembles classes 'main'.
clean - Deletes the build directory.
jar - Assembles a jar archive containing the main classes.
testClasses - Assembles classes 'test'.

18. Tasks Continued…
Build Setup tasks
-----------------
init - Initializes a new Gradle build. [incubating]
wrapper - Generates Gradle wrapper files. [incubating]
Documentation tasks
-------------------
javadoc - Generates Javadoc API documentation for the
main source code.

19. Tasks Continue…
Help tasks
----------
components - Displays the components produced by root
project 'scratch'. [incubating]
dependencies - Displays all dependencies declared in root
project 'scratch'.
dependencyInsight - Displays the insight into a specific
dependency in root project 'scratch'.
help - Displays a help message.
model - Displays the configuration model of root project
'scratch'. [incubating]
projects - Displays the sub-projects of root project 'scratch'.
properties - Displays the properties of root project 'scratch'.
tasks - Displays the tasks runnable from root project 'scratch'.
Verification tasks
------------------
check - Runs all checks.
test - Runs the unit tests.

20. Sample Output
gradle build
src
build
scratch-1.0-SNAPSHOT.jar
libs
project
Output

21. Projects versus Tasks
Project 1 Project 2
Project 3
Task 1
Task 3
Task 2
Depends on
Task 1
Task 2
Depends on
Task 1
Task 3
Task 2
Depends on
Task 3
Depends on

22. Understanding build.gradle
org.gradle.api.Project
apply(options: Map<String,?>)
buildscript(config: Closure)
dependencies(config: Closure)
configurations(config: Closure)
getDependencies()
getConfigurations()
getAnt()
getName()
getDescription()
getGroup()
getPath()
getVersion()
getLogger()
setDescription(description: String)
setVersion(version: Object)
file(path: Object)
task(args: Map<String,?>,name: String)
Project is an implicit object.
Project.apply plugin: ‘java

23. Understanding Gradle Tasks
org.gradle.api.Task
dependsOn(tasks: Object…)
doFirst(action: Closure)
doLast(action: Closure)
getActions()
getInputs()
getOutputs()
getAnt()
getDescription()
getEnabled()
getGroup()
setDescription(description: String)
setEnabled(enabled: boolean)
setGroup(group: String)
Tasks are built on the Task object.

24. Defining Tasks

25. Task Dependencies

26. Grouping Tasks

27. Grouping Tasks
Custom Group

28. Plugins
Plugin ID Automatically
Applies
Works With Description
java java-base Java compilation/testing
application java,distribution
ear java Java EE Support
maven java,war Maven publishing
war java Assembles WAR files
java-library-
distribution
java, distribution Support for tar/zip
distributions for Java
library.
idea java Generates IDEA files
eclipse java,groovy,
scala
Generates Eclipse files
Standard: https://docs.gradle.org/current/userguide/standard_plugins.html
Third party: https://plugins.gradle.org

29. Multi-Module Projects

30. Multi-Module Projects
admin-web
model
myApp
web
mobile-app
build.gradle
gradle.properties
admin-web
model
myApp
web
mobile-app
build.gradle
gradle.properties
master
Hierarchical Layout Flat Layout

31. Hierarchical Layout: Example Project
ctjava
build.gradle
settings.gradle
ctcore
build.gradle
settings.gradle
ctweb
build.gradle
settings.gradle
migrate
build.gradle
settings.gradle

32. Hierarchical Layout: Top Level
build.gradle gradle.settings
ctjava

33. Hierarchical Layout: Second Level
 gradle.settings for ctcore/migrate/ctweb:
rootProject.name = 'ctjava’
 migrate/ctweb dependencies on ctcore
compile project (':ctcore’)

34. IDE Support

35. IDE Support
IDE Separate Plugin Java EE Support
IDEA (free) No Yes
IDEA (paid) No Yes
NetBeans Yes Yes
Eclipse Yes Yes

36. Eclipse Gradle Support
 http://download.eclipse.org/buildship/updates/e46/r
eleases/1.0

37. NetBeans Gradle Support
Multi-project Java EE projects not recognized.

38. IntelliJ Support

39. Legacy Project

40. NetBeans EE Project to Gradle
File System Project Representation

41. NetBeans EE Project to Gradle
Java Source
directories
WAR Plugin
Local JARs

42. NetBeans EE Project to Gradle
Web resource
directory
Java EE
Dependencies
Local JAR
Continued…

43. WAR Plugin Configuration
Configuration Description
from Adds a file-set to the root of the archive
webInf Adds a file-set to the WEB-INF dir.
classpath Adds a file-set to the WEB-INF/lib dir
webAppDirName The name of the web application source directory, relative
to the project directory.
webXml Copies a file to WEB-INF/web.xml

44. Recipes

45. JavaScript Minification
Minification Output
Google Minifier

46. JavaScript Minification…
 Extend JavaExec Task to invoke Minifier

47. JavaScript Minification…
gradle -PjsOptimize=true build

48. Node/Webpack Integration
Node Gradle Plugin
https://github.com/srs/gradle-node-plugin
Supports: NodeJS, Yarn, Grunt, Gulp

49. Generating JPA Meta-Model
Create custom plugin to run Java Annotation Processor:
implementation-class=JavaAptPlugin

50. Custom Annotation Processor
Custom annotation processor

51. Custom Annotation Processor
Custom annotation processor

52. Custom Annotation Processor:
Build Plugin
Exclude everything
but JPA entities
Custom annotation processor

53. EAR Projects
Project Output
Contents of EAR

54. EAR Project
EAR plugin

55. Provided Scope – Non-WAR Projects
• providedCompile is a configuration on WAR plugin.
• Non-WAR projects must add a custom scope.

56. jaxb Code Generation
POJOxsd

57. Generating JAX-WS Client
 Generate JAX-WS client for WSDL using wsimport
 Plugin:
 https://plugins.gradle.org/plugin/me.seeber.wsimport
 Generated source code:
 build/generated-src/wsimport

58. Generating JAX-WS Client
https://plugins.gradle.org/plugin/me.seeber.wsimport

59. Generating JAX-WS Client
Generated Source Code

60. Docker
 Build Docker images from project output:
 Transmode/gradle-docker - http://tinyurl.com/k7o7nab
 Build/publish docker files from build script – not Dockerfile
 bmuschko/gradle-docker-plugin -
http://tinyurl.com/hg4q6jr
 docker-remote-api – interacts with Docker via remote API
 docker-java-application – creates/pushes docker images for java
applications
 Run Docker containers during build
 palantir/gradle-docker - http://tinyurl.com/hpw853h
 docker – building and pushing docker images
 docker-compose - populating placeholders in a docker-compose
template
 docker-run – starting/stopping/status on named images

61. Building Docker Images

62. Simple Docker Example – Run
Container
Available Tasks:
• dockerRun
• dockerStop
• dockerRunStatus
• dockerRemoveContainer

63. Docker & Testing
 Launch PostgreSQL Docker container before unit tests
execute
 Test cleanup:
 Leave container running if any tests fail
 Destroy container if tests succeed

64. Docker & Testing

65. Docker Database Testing

66. Parameter Substitution: persistence.xml

67. Parameter Substitution: build.gradle

68. Testing with Arquillian/Selenium

69. Misc
 View Dependencies:
gradle -q ctweb:dependencies
 Build GUI:
gradle –gui
 Profiling:
gradle –profile
 Dryrun
gradle –m build

70. Reasons to Convert
 Incremental compilation
 Better dependency management/control
 Customizable without needing plugins
 Supports multiple languages/platforms
 Build system can be versioned

71. Q&A