1 Introduction 2.3.8

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(Quick Reference) # 1 Introduction - Reference Documentation Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari Version: 2.3.8 ## Table of Contents # 1 Introduction Java web development as it stands today is dramatically more complicated than it needs to be. Most modern web frameworks in the Java space are over complicated and don't embrace the Don't Repeat Yourself (DRY) principles. Dynamic frameworks like Rails, Django and TurboGears helped pave the way to a more modern way of thinking about web applications. Grails builds on these concepts and dramatically reduces the complexity of building web applications on the Java platform. What makes it different, however, is that it does so by building on already established Java technologies like Spring and Hibernate. Grails is a full stack framework and attempts to solve as many pieces of the web development puzzle through the core technology and its associated plugins. Included out the box are things like: An easy to use Object Relational Mapping (ORM) layer built on Hibernate An expressive view technology called Groovy Server Pages (GSP) A controller layer built on Spring MVC A command line scripting environment built on the Groovy-powered Gant An embedded Tomcat container which is configured for on the fly reloading Dependency injection with the inbuilt Spring container Support for internationalization (i18n) built on Spring's core MessageSource concept A transactional service layer built on Spring's transaction abstraction All of these are made easy to use through the power of the Groovy language and the extensive use of Domain Specific Languages (DSLs) This documentation will take you through getting started with Grails and building web applications with the Grails framework. ## 1.1 What's new in Grails 2.3? #### Improved Dependency Management The default dependency resolution engine used by Grails has been changed to Aether, the dependency resolution engine used by Maven. Which engine you use can be configured in `BuildConfig`:
    grails.project.dependency.resolver = "maven" // or ivy
Using Aether dependency resolution in Grails results in the same behavior as when using the Maven build tool, meaning improved snapshot handling, understanding of custom packaging types and so on. In addition, the dependency-report command has been updated to print the dependency graph of the console, which helps in diagnosing dependency resolution failures. See the chapter on Dependency Resolution for more information. #### Data Binder Grails 2.3 includes a new data binding mechanism which is more flexible and easier to maintain than the data binder used in previous versions. The new data binder includes numerous enhancements including: Custom date formats on a per field basis using BindingFormat User defined data converters using ValueConverter User defined formatted data converters using BindingFormat and FormattedValueConverter Custom binding on a per class basis using BindUsing Custom binding on a per field basis using BindUsing By default all blank and empty Strings will be converted to null during data binding (configurable) See the Data Binding section for details. The legacy data binder may be used by assigning `true` to the `grails.databinding.useSpringBinder` property in `grails-app/conf/Config.groovy`. Note that the legacy binder does not support any of the new features provided by the new data binder. #### Binding Request Body To Command Objects If a request is made to a controller action which accepts a command object and the request includes a body, the body will be parsed and used to do data binding to the command object. This simplifies use cases where a request includes a JSON or XML body (for example) that can be bound to a command object. See the Command Objects documentation for more details. #### Domain Classes As Command Objects When a domain class is used as a command object and there is an `id` request parameter, the framework will retrieve the instance of the domain class from the database using the `id` request parameter. See the Command Objects documentation for more details. #### Forked Execution All major commands can now be forked into a separate JVM, thus isolating the build path from the runtime / test paths. Forked execution can be controlled via the `BuildConfig`:
    grails.project.fork = [
       test: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256, daemon:true], // configure settings for the test-app JVM
       run: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256], // configure settings for the run-app JVM
       war: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256], // configure settings for the run-war JVM
       console: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256]// configure settings for the Console UI JVM
    ]
See the documentation on Forked Mode for more information. #### Test Runner Daemon To speed up testing when using forked execution a new daemon will start-up in the background to run tests when using interactive mode. You can restart the daemon with the `restart-daemon` command from interactive mode:
    $ grails> restart-daemon
#### Server-Side REST Improvements Grails' REST support has been significantly improved with the addition of the following features: Rich REST URL Mapping support with supports for resource mappings, singular resource mappings, nested resources, versioning and more New extensible response rendering and binding APIs Support for HAL, Atom and Hypermedia (HATEAOS) Scaffolding for REST controllers See the user guide for more information. #### New Scaffolding 2.0 Plugin Grails' Scaffolding feature has been split into a separate plugin. Version 2.0 of the plugin includes support for generating REST controllers, Async controllers, and Spock unit tests. #### URL Mappings May Specify A Redirect URL Mappings may now specify that a redirect should be triggered when the mapping matches an incoming request:

    class UrlMappings {
        static mappings = {
            "/viewBooks"(redirect: '/books/list')
            "/viewAuthors"(redirect: [controller: 'author', action: 'list'])
            "/viewPublishers"(redirect: [controller: 'publisher', action: 'list', permanent: true])        // …
        }
    }
See the user guide for more information. #### Async support Grails 2.3 features new Asynchronous Programming APIs that allow for asynchronous processing of requests and integrate seamlessly with GORM. Example:
    import static grails.async.Promises.*
    …
    def index() {
       tasks books: Book.async.list(),
             totalBooks: Book.async.count(),
             otherValue: {
               // do hard work
             }
    }
See the documentation for further information. #### Encoding / Escaping Improvements Grails 2.3 features dedicated support for Cross Site Scripting (XSS) prevention, including : Defaulting to HTML escaping all GSP expressions and scriptlets Context sensitive encoding switching for tags Double encoding prevention Optional automatic encoding of all data in a GSP page not considered safe See the documentation on Cross Site Scripting (XSS) prevention for more information. #### Hibernate 3 and 4 support The GORM for Hibernate 3 support for Grails has been extracted into a separate project, allowing new support for Hibernate 4 as a separate plugin. #### Controller Exception Handling Controllers may define exception handler methods which will automatically be invoked any time an action in that controller throws an exception.

    // grails-app/controllers/demo/DemoController.groovy
    package democlass DemoController {    def someAction() {
            // do some work
        }    def handleSQLException(SQLException e) {
            render 'A SQLException Was Handled'
        }    def handleBatchUpdateException(BatchUpdateException e) {
            redirect controller: 'logging', action: 'batchProblem'
        }    def handleNumberFormatException(NumberFormatException nfe) {
            [problemDescription: 'A Number Was Invalid']
        }
    }
See the controller exception handling docs for more information. #### Namespaced Controllers Controllers may now be defined in a namespace which allows for multiple controllers to be defined with the same name in different packages.

    // grails-app/controllers/com/app/reporting/AdminController.groovy
    package com.app.reportingclass AdminController {    static namespace = 'reports'    // …
    }

    // grails-app/controllers/com/app/security/AdminController.groovy
    package com.app.securityclass AdminController {    static namespace = 'users'    // …
    }

    // grails-app/conf/UrlMappings.groovy
    class UrlMappings {    static mappings = {
            '/userAdmin' {
                controller = 'admin'
                namespace = 'users'
            }        '/reportAdmin' {
                controller = 'admin'
                namespace = 'reports'
            }        "/$namespace/$controller/$action?"()
        }
    }
    <g:link controller="admin" namespace="reports">Click For Report Admin</g:link>
    <g:link controller="admin" namespace="users">Click For User Admin</g:link>
See the namespaced controllers docs for more information. #### Command Line The `create-app` command will now by default generate the command line grailsw wrapper for newly created applications. The `--skip-wrapper` switch may be used to prevent the wrapper from being generated.
    grails create-app appname --skip-wrapper
## 1.2 What's new in Grails 2.2? #### Namespace Support Grails 2.2 includes improved support for managing naming conflicts between artifacts provided by an application and its plugins. Bean names for Service artifacts provided by a plugin are now prefixed with the plugin name. For example, if a Service named `com.publishing.AuthorService` is provided by a plugin named `PublishingUtilities` and another Service named `com.bookutils.AuthorService` is provided by a plugin named `BookUtilities`, the bean names for those services will be `publishingUtilitiesAuthorService` and `bookUtilitiesAuthorService` respectively. If a plugin provides a Service that does not have a name which conflicts with any other Service, then a bean alias will automatically be created that does not contain the prefix and the alias will refer to the bean referenced by the prefixed name. Service artifacts provided directly by the application will have no prefix added to the relevant bean name. See the dependency injection and services docs. Domain classes provided by a plugin will have their default database table name prefixed with the plugin name if the `grails.gorm.table.prefix.enabled` config property is set to `true`. For example, if the `PublishingUtilities` plugin provides a domain class named `Book`, the default table name for that domain class will be `PUBLISHING_UTILITIES_BOOK` if the `grails.gorm.table.prefix.enabled` config property is set to `true`. URL Mappings may now include a `plugin` attribute to indicate that the controller referenced in the mapping is provided by a particular plugin.

    static mappings = {    // requests to /bookAuthors will be handled by the
        // AuthorController provided by the BookUtilities plugin
        "/bookAuthors" {
            controller = 'author'
            plugin = 'bookUtilities'
        }    // requests to /publishingAuthors will be handled by the
        // AuthorController provided by the Publishing plugin
        "/publishingAuthors" {
            controller = 'author'
            plugin = 'publishing'
        }
    }
See the namespaced controllers docs for more information. Controller methods and GSP Tags which accept a controller name as a parameter now support an optional parameter indicating that the controller is provided by a specific plugin.
    <g:link controller="user" plugin="springSecurity">Manage Users</g:link>
    class DemoController {
        def index() {
            redirect controller: 'user', action: 'list', plugin: 'springSecurity'
        }
    }
#### Forked Tomcat Execution Grails 2.2 supports forked JVM execution of the Tomcat container in development mode. This has several benefits including: Reduced memory consumption, since the Grails build system can exit Isolation of the build classpath from the runtime classpath The ability to deploy other Grails/Spring applications in parallel without conflicting dependencies See the documentation on using forked mode for more information. #### SQL Projections In Criteria Queries Grails 2.2 adds new functionality to criteria queries to provide access to Hibernate's SQL projection API.

    // Use SQL projections to retrieve the perimeter and area of all of the Box instances…
    def c = Box.createCriteria()def results = c.list {
        projections {
          sqlProjection '(2 * (width + height)) as perimiter, (width * height) as area', ['perimeter', 'area'], [INTEGER, INTEGER]
        }
    }
See the Criteria section for more information. #### Groovy 2 Grails 2.2 ships with Groovy 2.0, which has a bunch of new features itself. ## 1.3 What's new in Grails 2.1? #### Maven Improvements / Multi Module Build Support Grails' Maven support has been improved in a number of significant ways. Firstly it is now possible to specify plugins within your `pom.xml` file:
    <dependency>
        <groupId>org.grails.plugins</groupId>
        <artifactId>hibernate</artifactId>
        <version>2.1.0</version>
        <type>zip</type>
        <scope>compile</scope>
    </dependency>
The Maven plugin now resolves plugins as well as jar dependencies (previously jar dependencies were resolved by Maven and plugins by Ivy). Ivy is completely disabled leaving all dependency resolution up to Maven ensuring that evictions work as expected. There is also a new Grails `create-multi-project-build` script which features initial support for Maven (Gradle coming in a future release). This script can be run from a parent directory containing Grails applications and plugins and it will generate a Maven multi-module build. Enabling Maven in a project has been made easier with the inclusion of the `create-pom` command:
    grails create-app myapp
    cd myapp
    grails create-pom com.mycompany
    mvn package
To create a multi-module Maven build follow these steps:
    grails create-app myapp
    grails create-plugin plugin-a
    grails create-plugin plugin-b
    grails create-multi-project-build com.mycompany:parent:1.0-SNAPSHOT
    mvn install
#### Grails Wrapper The Grails Wrapper allows a Grails application to build without having to install Grails and configure a GRAILS_HOME environment variable. The wrapper includes a small shell script and a couple of small bootstrap jar files that typically would be checked in to source code control along with the rest of the project. The first time the wrapper is executed it will download and configure a Grails installation. This wrapper makes it more simple to setup a development environment, configure CI and manage upgrades to future versions of Grails. When the application is upgraded to the next version of Grails, the wrapper is updated and checked in to the source code control system and the next time developers update their workspace and run the wrapper, they will automatically be using the correct version of Grails. See the Wrapper Documentation for more details. #### Debug Option The `grails` command now supports a `-debug` option which will startup the remote debug agent. This behavior used to be provided by the `grails-debug` command. `grails-debug` is still available but is deprecated and may be removed from a future release.
    grails -debug run-app
#### Grails Command Aliases The `alias` command may be used to define aliases for grails commands. The following command creates an alias named `rit` (short for "run integration tests"):
    grails alias rit test-app integration:
See the alias docs for more info. #### Cache Plugin Grails 2.1 installs the cache plugin by default. This plugin provides powerful and easy to use cache functionality to applications and plugins. The main plugin provides basic map backed caching support. For more robust caching options one of the implementation plugins should be installed and configured. See the cache-redis docs and the cache-ehcache docs for details. See the main plugin documentation for details on how to configure and use the plugin. #### New GORM Methods In Grails 2.1.1 domain classes now have static methods named `first` and `last` to retrieve the first and last instances from the datastore. See the first and last documentation for details. ## 1.4 What's new in Grails 2.0? This section covers the new features that are present in 2.0 and is broken down into sections covering the build system, core APIs, the web tier, persistence enhancements and improvements in testing. Note there are many more small enhancements and improvements, these sections just cover some of the highlights. ## 1.4.1 Development Environment Features #### Interactive Mode and Console Enhancements Grails 2.0 features brand new console output that is more concise and user friendly to consume. An example of the new output when running tests can be seen below: In general Grails makes its best effort to display update information on a single line and only present the information that is crucial. This means that while in previous versions of Grails the war command produced many lines of output, in Grails 2.0 only 1 line of output is produced: In addition simply typing 'grails' at the command line activates the new interactive mode which features TAB completion, command history and keeps the JVM running to ensure commands execute much quicker than otherwise For more information on the new features of the console refer to the section of the user guide that covers the console and interactive mode. #### Reloading Agent Grails 2.0 reloading mechanism no longer uses class loaders, but instead uses a JVM agent to reload changes to class files. This results in greatly improved reliability when reloading changes and also ensures that the class files stored in disk remain consistent with the class files loaded in memory, which reduces the need to run the clean command. #### New Test Report and Documentation Templates There are new templates for displaying test results that are clearer and more user friendly than the previous reports: In addition, the Grails documentation engine has received a facelift with a new template for presenting Grails application and plugin documentation: See the section on the documentation engine for more usage info. #### Use a TOC for Project Docs The old documentation engine relied on you putting section numbers into the gdoc filenames. Although convenient, this effectively made it difficult to restructure your user guide by inserting new chapters and sections. In addition, any such restructuring or renaming of section titles resulted in breaking changes to the URLs. You can now use logical names for your gdoc files and define the structure and section titles in a YAML table-of-contents file, as described in the section on the documentation engine. The logical names appear in the URLs, so as long as you don't change those, your URLs will always remain the same no matter how much restructuring or changing of titles you do. Grails 2.0 even provides a migrate-docs command to aid you in migrating existing gdoc user guides. #### Enhanced Error Reporting and Diagnosis Error reporting and problem diagnosis has been greatly improved with a new errors view that analyses stack traces and recursively displays problem areas in your code: In addition stack trace filtering has been further enhanced to display only relevant trace information:
    Line | Method
    ->>   9 | getValue     in Book.groovy
    - - - - - - - - - - - - - - - - - - - - - - - - -
    |     7 | getBookValue in BookService.groovy
    |   886 | runTask . .  in ThreadPoolExecutor.java
    |   908 | run          in     ''
    ^   662 | run . . . .  in Thread.java
#### H2 Database and Console Grails 2.0 now uses the H2 database instead of HSQLDB, and enables the H2 database console in development mode (at the URI /dbconsole) so that the in-memory database can be easily queried from the browser: #### Plugin Usage Tracking To enhance community awareness of the most popular plugins an opt-in plugin usage tracking system has been included where users can participate in providing feedback to the plugin community on which plugins are most popular. This will help drive the roadmap and increase support of key plugins while reducing the need to support older or less popular plugins thus helping plugin development teams focus their efforts. #### Dependency Resolution Improvements There are numerous improvements to dependency resolution handling via Ivy including: Grails now makes a best effort to cache the previous resolve and avoid resolving again unless you change `BuildConfig.groovy`. Plugins dependencies now appear in the dependency report generated by `grails dependency-report` Plugins published with the release plugin now publish their transitive plugin dependencies in the generated POM which are later resolved. It is now possible to customize the ivy cache directory via `BuildConfig.groovy`
    grails.project.dependency.resolution = {
        cacheDir "target/ivy-cache"
    }
You can change the ivy cache directory for all projects via `settings.groovy`
    grails.dependency.cache.dir = "${userHome}/.ivy2/cache"
It is now possible to completely disable resolution from inherited repositories (repositories defined by other plugins):

    grails.project.dependency.resolution = {    repositories {
            inherits false // Whether to inherit repository definitions from plugins
            …
        }
        …
    }
It is now possible to easily disable checksum validation errors:
    grails.project.dependency.resolution = {
        checksums false // whether to verify checksums or not
    }
## 1.4.2 Core Features #### Binary Plugins Grails plugins can now be packaged as JAR files and published to standard maven repositories. This even works for GSP and static resources (with resources plugin 1.0.1). See the section on Binary plugins for more information. #### Groovy 1.8 Grails 2.0 comes with Groovy 1.8 which includes many new features and enhancements #### Spring 3.1 Profile Support Grails' existing environment support has been bridged into the Spring 3.1 profile support. For example when running with a custom Grails environment called "production", a Spring profile of "production" is activated so that you can use Spring's bean configuration APIs to configure beans for a specific profile. ## 1.4.3 Web Features #### Controller Actions as Methods It is now possible to define controller actions as methods instead of using closures as in previous versions of Grails. In fact this is now the preferred way of expressing an action. For example:

    // action as a method
    def index() {}
    // action as a closure
    def index = {}
#### Binding Primitive Method Action Arguments It is now possible to bind form parameters to action arguments where the name of the form element matches the argument name. For example given the following form:
    <g:form name="myForm" action="save">
        <input name="name" />
        <input name="age" />
    </g:form>
You can define an action that declares arguments for each input and automatically converts the parameters to the appropriate type:
    def save(String name, int age) {
        // remaining
    }
#### Static Resource Abstraction A new static resource abstraction is included that allows declarative handling of JavaScript, CSS and image resources including automatic ordering, compression, caching and gzip handling. #### Servlet 3.0 Async Features Grails now supports Servlet 3.0 including the Asynchronous programming model defined by the specification:
    def index() {
        def ctx = startAsync()
        ctx.start {
            new Book(title:"The Stand").save()
            render template:"books", model:[books:Book.list()]
            ctx.complete()
        }
    }
#### Link Generation API A general purpose `LinkGenerator` class is now available that is usable anywhere within a Grails application and not just within the context of a controller. For example if you need to generate links in a service or an asynchronous background job outside the scope of a request:

    LinkGenerator grailsLinkGeneratordef generateLink() {
        grailsLinkGenerator.link(controller:"book", action:"list")
    }
#### Page Rendering API Like the `LinkGenerator` the new `PageRenderer` can be used to render GSP pages outside the scope of a web request, such as in a scheduled job or web service. The `PageRenderer` class features a very similar API to the `render` method found within controllers:

    grails.gsp.PageRenderer groovyPageRenderervoid welcomeUser(User user) {
        def contents = groovyPageRenderer.render(view:"/emails/welcomeLetter", model:[user: user])
        sendEmail {
            to user.email
            body contents
        }
    }
The `PageRenderer` service also allows you to pre-process GSPs into HTML templates:
    new File("/path/to/welcome.html").withWriter { w ->
        groovyPageRenderer.renderTo(view:"/page/content", w)
    }
#### Filter Exclusions Filters may now express controller, action and uri exclusions to offer more options for expressing to which requests a particular filter should be applied.

    filter1(actionExclude: 'log*') {
        before = {
            // …
        }
    }
    filter2(controllerExclude: 'auth') {
        before = {
            // …
        }
    }filter3(uriExclude: '/secure*') {
        before = {
            // …
        }
    }
#### Performance Improvements Performance of GSP page rendering has once again been improved by optimizing the GSP compiler to inline method calls where possible. #### HTML5 Scaffolding There is a new HTML5-based scaffolding UI: #### jQuery by Default The jQuery plugin is now the default JavaScript library installed into a Grails application. For backwards compatibility a Prototype plugin is available. Refer to the documentation on the Prototype plugin for installation instructions. #### Easy Date Parsing A new `date` method has been added to the `params` object to allow easy, null-safe parsing of dates:

    def val = params.date('myDate', 'dd-MM-yyyy')// or a list for formats
    def val = params.date('myDate', ['yyyy-MM-dd', 'yyyyMMdd', 'yyMMdd'])// or the format read from messages.properties via the key 'date.myDate.format'
    def val = params.date('myDate')
#### Customizable URL Formats The default URL Mapping mechanism supports camel case names in the URLs. The default URL for accessing an action named `addNumbers` in a controller named `MathHelperController` would be something like `/mathHelper/addNumbers`. Grails allows for the customization of this pattern and provides an implementation which replaces the camel case convention with a hyphenated convention that would support URLs like `/math-helper/add-numbers`. To enable hyphenated URLs assign a value of "hyphenated" to the `grails.web.url.converter` property in `grails-app/conf/Config.groovy`.

    // grails-app/conf/Config.groovygrails.web.url.converter = 'hyphenated'
Arbitrary strategies may be plugged in by providing a class which implements the UrlConverter interface and adding an instance of that class to the Spring application context with the bean name of `grails.web.UrlConverter.BEAN_NAME`. If Grails finds a bean in the context with that name, it will be used as the default converter and there is no need to assign a value to the `grails.web.url.converter` config property.

    // src/groovy/com/myapplication/MyUrlConverterImpl.groovypackage com.myapplicationclass MyUrlConverterImpl implements grails.web.UrlConverter {    String toUrlElement(String propertyOrClassName) {
            // return some representation of a property or class name that should be used in URLs…
        }
    }

    // grails-app/conf/spring/resources.groovybeans = {
        "${grails.web.UrlConverter.BEAN_NAME}"(com.myapplication.MyUrlConverterImpl)
    }
#### Web Flow input and output It is now possible to provide input arguments when calling a subflow. Flows can also return output values that can be used in a calling flow. ## 1.4.4 Persistence Features #### The GORM API The GORM API has been formalized into a set of classes (`GormStaticApi`, `GormInstanceApi` and `GormValidationApi`) that get statically wired into every domain class at the byte code level. The result is better code completion for IDEs, better integration with Java and the potential for more GORM implementations for other types of data stores. #### Detached Criteria and Where Queries Grails 2.0 features support for DetachedCriteria which are criteria queries that are not associated with any session or connection and thus can be more easily reused and composed:
    def criteria = new DetachedCriteria(Person).build {
        eq 'lastName', 'Simpson'
    }
    def results = criteria.list(max:4, sort:"firstName")
To support the addition of DetachedCriteria queries and encourage their use a new `where` method and DSL has been introduced to greatly reduce the complexity of criteria queries:
    def query = Person.where {
        (lastName != "Simpson" && firstName != "Fred") || (firstName == "Bart" && age > 9)
    }
    def results = query.list(sort:"firstName")
See the documentation on DetachedCriteria and Where Queries for more information. #### New findOrCreate and findOrSave Methods Domain classes have support for the findOrCreateWhere, findOrSaveWhere, findOrCreateBy and findOrSaveBy query methods which behave just like findWhere and findBy methods except that they should never return null. If a matching instance cannot be found in the database then a new instance is created, populated with values represented in the query parameters and returned. In the case of findOrSaveWhere and findOrSaveBy, the instance is saved before being returned.
    def book = Book.findOrCreateWhere(author: 'Douglas Adams', title: "The Hitchiker's Guide To The Galaxy")
    def book = Book.findOrSaveWhere(author: 'Daniel Suarez', title: 'Daemon')
    def book = Book.findOrCreateByAuthorAndTitle('Daniel Suarez', 'Daemon')
    def book = Book.findOrSaveByAuthorAndTitle('Daniel Suarez', 'Daemon')
#### Abstract Inheritance GORM now supports abstract inheritance trees which means you can define queries and associations linking to abstract classes:

    abstract class Media {
        String title
        …
    }
    class Book extends Media {
    }
    class Album extends Media {}
    class Account {
        static hasMany = [purchasedMedia:Media]
    }..def allMedia = Media.list()
#### Multiple Data Sources Support It is now possible to define multiple datasources in `DataSource.groovy` and declare one or more datasources a particular domain uses by default:

    class ZipCode {   String code   static mapping = {
          datasource 'ZIP_CODES'
       }
    }
If multiple datasources are specified for a domain then you can use the name of a particular datasource as a namespace in front of any regular GORM method:
    def zipCode = ZipCode.auditing.get(42)
For more information see the section on Multiple Data Sources in the user guide. #### Database Migrations A new database migration plugin has been designed and built for Grails 2.0 allowing you to apply migrations to your database, rollback changes and diff your domain model with the current state of the database. #### Database Reverse Engineering A new database reverse engineering plugin has been designed and built for Grails 2.0 that allows you to generate a domain model from an existing database schema. #### Hibernate 3.6 Grails 2.0 is now built on Hibernate 3.6 #### Bag Collections You can now use Hibernate Bags for mapped collections to avoid the memory and performance issues of loading large collections to enforce `Set` uniqueness or `List` order. For more information see the section on Sets, Lists and Maps in the user guide. ## 1.4.5 Testing Features #### New Unit Testing Console Output Test output from the test-app command has been improved: #### New Unit Testing API There is a new unit testing API based on mixins that supports JUnit 3, 4 and Spock style tests (with Spock 0.6 and above). Example:

    import grails.test.mixin.TestFor@TestFor(SimpleController)
    class SimpleControllerTests  {
        void testIndex() {
            controller.home()        assert view == "/simple/homePage"
            assert model.title == "Hello World"
        }
    }
The documentation on testing has also been re-written around this new framework. #### Unit Testing GORM A new in-memory GORM implementation is present that supports many more features of the GORM API making unit testing of criteria queries, named queries and other previously unsupported methods possible. #### Faster Unit Testing with Interactive Mode The new interactive mode (activated by typing 'grails') greatly improves the execution time of running unit and integration tests. #### Unit Test Scaffolding A unit test is now generated for scaffolded controllers | Quick Reference (hide)