Introduction to GrailsIntroduction to Grails

Christopher BartlingChristopher Bartling

TopicsTopics

Decomposing Grails

Major components

Extending Grails with plugins

Demostrations

Basic Grails commands

Book Club

Questions

Decomposing Grails

Major components

Extending Grails with plugins

Demostrations

Basic Grails commands

Book Club

Questions

What is Grails?What is Grails?

Next generation web framework for the JVM

Focus on developer productivity

Dynamic language - Groovy

Convention over Configuration

Pragmatic tooling promotes agility

DSLs, code generators, dependency resolution, multi-environment configuration

Next generation web framework for the JVM

Focus on developer productivity

Dynamic language - Groovy

Convention over Configuration

Pragmatic tooling promotes agility

DSLs, code generators, dependency resolution, multi-environment configuration

Under the hoodUnder the hood

Grails utilizes a lot of existing Java frameworks

Spring Framework: Dependency injection, AOP, core abstractions

Spring MVC: Web application framework

Hibernate: Relational database persistence

SiteMesh: Web layout and templating

Servlet API: Core web application infrastructure

Grails utilizes a lot of existing Java frameworks

Spring Framework: Dependency injection, AOP, core abstractions

Spring MVC: Web application framework

Hibernate: Relational database persistence

SiteMesh: Web layout and templating

Servlet API: Core web application infrastructure

Decomposing GrailsDecomposing Grails

Grails scripts and Gant

Model-View-Controller (MVC) design

Grails Object Relational Mapping (GORM)

Services

Dependency resolution and configuration

Plugins

Grails scripts and Gant

Model-View-Controller (MVC) design

Grails Object Relational Mapping (GORM)

Services

Dependency resolution and configuration

Plugins

Grails scriptsGrails scripts

Generate various parts of the Grails application

create-app: Creates a blank Grails application

create-domain-class: Creates a new domain object

generate-all: Generates the controller and associated views for a domain object

run-app: Runs the Grails application in the bundled Tomcat engine

Generate various parts of the Grails application

create-app: Creates a blank Grails application

create-domain-class: Creates a new domain object

generate-all: Generates the controller and associated views for a domain object

run-app: Runs the Grails application in the bundled Tomcat engine

GantGant

Grails build system

Thin DSL wrapper around Apache Ant

Gant scripts reside in grails-app/scripts directory

Create a new script:

grails create-script [scriptName]

Grails build system

Thin DSL wrapper around Apache Ant

Gant scripts reside in grails-app/scripts directory

Create a new script:

grails create-script [scriptName]

Domain objects (Model)Domain objects (Model)

Automatically mapped to database schema

Can tweak mapping through DSL on domain class

Object relationship management

DSL on domain class

Attribute and object validation

Configured through DSL on domain class

Automatically mapped to database schema

Can tweak mapping through DSL on domain class

Object relationship management

DSL on domain class

Attribute and object validation

Configured through DSL on domain class

Domain class exampleDomain class example

class Book {

String title

String author

String description

Date reviewDate

static hasMany = [comments: Comment]

static constraints = {

title nullable: false, blank: false, size: 1..1024

author nullable: false, blank: false, size: 2..255

description nullable:true, blank: true, maxSize: 1000000

reviewDate nullable: true

}

}

class Book {

String title

String author

String description

Date reviewDate

static hasMany = [comments: Comment]

static constraints = {

title nullable: false, blank: false, size: 1..1024

author nullable: false, blank: false, size: 2..255

description nullable:true, blank: true, maxSize: 1000000

reviewDate nullable: true

}

}

GORMGORM

The default Grails persistence layer

Functionality for reading, listing, sorting, counting, saving, and deleting objects

Relationship management

Dynamic finder and counting methods

Criteria, HQL, and SQL queries

Pagination support

The default Grails persistence layer

Functionality for reading, listing, sorting, counting, saving, and deleting objects

Relationship management

Dynamic finder and counting methods

Criteria, HQL, and SQL queries

Pagination support

Domain class dynamic runtime methodsDomain class dynamic runtime methods

Groovy provides method interception support

Grails injects several methods on all domain objects at runtime

get(id), getAll([id, id, id, …]), list(), listOrderBy*()

findBy*(), findAllBy*(), count(), countBy*()

save(), delete(), validate(), hasErrors

withTransaction, withCriteria

Groovy provides method interception support

Grails injects several methods on all domain objects at runtime

get(id), getAll([id, id, id, …]), list(), listOrderBy*()

findBy*(), findAllBy*(), count(), countBy*()

save(), delete(), validate(), hasErrors

withTransaction, withCriteria

Synthesized domain methodsSynthesized domain methods

The countBy*() and findBy*() methods are synthesized from domain class properties and the following comparators:

Equal, NotEqual, LessThan, LessThanEquals, GreaterThan, GreaterThanEquals, Like, like (case insensitive), InList, Between, IsNull, IsNotNull

This support works for up to two properties with optional comparators and logical operator

The countBy*() and findBy*() methods are synthesized from domain class properties and the following comparators:

Equal, NotEqual, LessThan, LessThanEquals, GreaterThan, GreaterThanEquals, Like, like (case insensitive), InList, Between, IsNull, IsNotNull

This support works for up to two properties with optional comparators and logical operator

Domain class constraint validationDomain class constraint validation

The domain class’s save() and validate() methods will trigger data validation

Domain object maintains validation errors collection

17 built-in constraints

The validator constraint supports custom validation scenarios

Many of the domain constraints influence database schema generation

The domain class’s save() and validate() methods will trigger data validation

Domain object maintains validation errors collection

17 built-in constraints

The validator constraint supports custom validation scenarios

Many of the domain constraints influence database schema generation

Domain classes: One-to-one relationshipsDomain classes: One-to-one relationships

One class references another

Declared by a property of the type of referenced domain class

Bi-directional one-to-one: Each class has a property to the other domain class

Ownership and cascading updates are declared with the static belongsTo property

One class references another

Declared by a property of the type of referenced domain class

Bi-directional one-to-one: Each class has a property to the other domain class

Ownership and cascading updates are declared with the static belongsTo property

Domain classes: One-to-many relationshipsDomain classes: One-to-many relationships

Uni-directional one-to-many relationship uses the static hasMany property

The static belongsTo property can also be used in this relationship scenario

Bi-directional one-to-many relationship is as easy as adding a reference for the parent object reference and using the static belongsTo property

Uni-directional one-to-many relationship uses the static hasMany property

The static belongsTo property can also be used in this relationship scenario

Bi-directional one-to-many relationship is as easy as adding a reference for the parent object reference and using the static belongsTo property

Domain classes: Many-to-many relationshipsDomain classes: Many-to-many relationships

Declared by adding a static hasMany property to each class participating in the relationship

One of the classes must declare a static belongsTo property to properly set ownership of the relationship

Declared by adding a static hasMany property to each class participating in the relationship

One of the classes must declare a static belongsTo property to properly set ownership of the relationship

ControllersControllers

Groovy class with name ending in “Controller”

Resides in grails-app/controllers directory

Dynamically receive methods and properties at runtime

Any closure defined as a property of the controller becomes an action reachable by URL

book-club/book/add

Groovy class with name ending in “Controller”

Resides in grails-app/controllers directory

Dynamically receive methods and properties at runtime

Any closure defined as a property of the controller becomes an action reachable by URL

book-club/book/add

Controller responsesController responses

Return a map of data or nothing

Controller forwards execution control to view of the same name as action

Redirect to another action or URL

Render output directly

Rendering can be a view, template, JSON, XML, binary

JSON and XML converters part of Grails

Return a map of data or nothing

Controller forwards execution control to view of the same name as action

Redirect to another action or URL

Render output directly

Rendering can be a view, template, JSON, XML, binary

JSON and XML converters part of Grails

UrlMappings.groovyUrlMappings.groovy

Resides in grails-app/conf directory

DSL for customizing the mapping of the URIs to controller actions

Use this file to implement RESTful web service URIs

Error status codes can also be mapped to custom error pages

Resides in grails-app/conf directory

DSL for customizing the mapping of the URIs to controller actions

Use this file to implement RESTful web service URIs

Error status codes can also be mapped to custom error pages

ViewsViews

Each controller will have a corresponding directory under grails-app/views for views

e.g. grails-app/views/book

Groovy Server Pages (GSPs) reside here

View rendering convention: Forward to view GSP named the same as controller action

This is very customizable

Each controller will have a corresponding directory under grails-app/views for views

e.g. grails-app/views/book

Groovy Server Pages (GSPs) reside here

View rendering convention: Forward to view GSP named the same as controller action

This is very customizable

Groovy Server Pages (GSPs)Groovy Server Pages (GSPs)

View rendering

Reside in the grails-app/views directory

Grails provides about 50 tags for use in GSPs

Logical, looping, link creation, forms and form inputs, JavaScript and other resource management tags

Custom taglibs are easily created for use in GSPs

View rendering

Reside in the grails-app/views directory

Grails provides about 50 tags for use in GSPs

Logical, looping, link creation, forms and form inputs, JavaScript and other resource management tags

Custom taglibs are easily created for use in GSPs

Tag librariesTag libraries

Reside in grails-app/taglib directory

Groovy class with name ending in “TagLib”

Taglib actions are just closure properties

Write output to OutputStream out

Automatically injected into your taglib instance

TagLib attributes become attributes on taglib XML

Reside in grails-app/taglib directory

Groovy class with name ending in “TagLib”

Taglib actions are just closure properties

Write output to OutputStream out

Automatically injected into your taglib instance

TagLib attributes become attributes on taglib XML

SiteMeshSiteMesh

Web page layout and decorator framework

Uses HTML meta tags to decorate your web page with standardized layout

Implemented as a page filter

Layout reside in grails-app/views/layouts

The main.gsp is your default layout master page

Web page layout and decorator framework

Uses HTML meta tags to decorate your web page with standardized layout

Implemented as a page filter

Layout reside in grails-app/views/layouts

The main.gsp is your default layout master page

ServicesServices

Reside in grails-app/services directory

Automatically have transaction support

static transactional = true | false

Automatically hosted by Spring DI container as singleton-scoped beans by default

Services can be injected into controllers, other services, domain classes

Reside in grails-app/services directory

Automatically have transaction support

static transactional = true | false

Automatically hosted by Spring DI container as singleton-scoped beans by default

Services can be injected into controllers, other services, domain classes

Dependency resolutionDependency resolution

Spring Framework is used to provide dependency injection

Spring bean configuration in resources.groovy

Spring DSL

Services will be autowired in controllers automatically

Spring Framework is used to provide dependency injection

Spring bean configuration in resources.groovy

Spring DSL

Services will be autowired in controllers automatically

Extending Grails with pluginsExtending Grails with plugins

At its heart, Grails is really just a plugin management system

Most of the major pieces of Grails are implemented as plugins

• http://grails.org/plugins/ hosts Grails plugins

• Currently about 575 plugins available!

• One of Grails big selling points

At its heart, Grails is really just a plugin management system

Most of the major pieces of Grails are implemented as plugins

• http://grails.org/plugins/ hosts Grails plugins

• Currently about 575 plugins available!

• One of Grails big selling points

Finding and installing Grails pluginsFinding and installing Grails plugins

• Listing plug-ins

• grails list-plugins

• Installing a plugin

• grails install-plugin [plugin-name] [version]

• Grails takes care of downloading, installing, and managing the plugin

• Listing plug-ins

• grails list-plugins

• Installing a plugin

• grails install-plugin [plugin-name] [version]

• Grails takes care of downloading, installing, and managing the plugin

Testing in GrailsTesting in Grails

• Grails creates unit test stubs

• Several GroovyTestCase subclasses specialized for testing Grails components

• Great mock object support

• mockDomain, mockForConstraintsTest, mockController, mockTagLib, mockLogging

• Integration testing supported with separate test environment configuration

• Grails creates unit test stubs

• Several GroovyTestCase subclasses specialized for testing Grails components

• Great mock object support

• mockDomain, mockForConstraintsTest, mockController, mockTagLib, mockLogging

• Integration testing supported with separate test environment configuration

Grails demonstrationsGrails demonstrations

Questions?Questions?

Resources available onlineResources available online

• Presentation and demo available on BitBucket.org

• https://bitbucket.org/cebartling/presentations

• Need Mercurial client to clone the repository or pull a zip archive snapshot of the repository

• Presentation and demo available on BitBucket.org

• https://bitbucket.org/cebartling/presentations

• Need Mercurial client to clone the repository or pull a zip archive snapshot of the repository

Contact informationContact information

• Christopher Bartling

• chris.bartling@gmail.com

• Twitter: @cbartling

• Blog: http://bartling.blogspot.com

• Christopher Bartling

• chris.bartling@gmail.com

• Twitter: @cbartling

• Blog: http://bartling.blogspot.com