3 Upgrading from Grails 2.2

New Data Binder

There is a new data binding mechanism written from the ground up to meet Grails' needs. If you wish to continue using Spring for data binding then you must set the grails.databinding.useSpringBinder property to true in grails-app/conf/Config.groovy

Dependency Resolution changes

Although dependency resolution using Ivy is still supported, the default for Grails 2.3 is to use Aether and the Ivy support will not be improved upon going forward. You may wish to consider using Aether instead for your existing applications by setting the following in grails-app/conf/BuildConfig.groovy:

grails.project.dependency.resolver = "maven" // or ivy

Dependency Metadata Changes

In addition, the POM and dependency metadata for Grails 2.3 has been re-arranged and cleaned up so that only direct dependencies are specified for an application and all other dependencies are inherited transitvely. This has implications to the upgrade since, for example, Ehcache is now a transitive dependency of the Hibernate plugin, whilst before it was a direct dependency. If get a compilation error related to Ehcache, it is most likely that you don't have the Hibernate plugin installed and need to directly declare the Ehcache dependency:

compile "net.sf.ehcache:ehcache-core:2.4.6"

In addition, excludes may no longer work and may need adjusting when upgrading due to how the metadata has changed. Run the dependency-report to see the new dependency metadata and make adjustments accordingly.

A common error that may occur when upgrading is:

| Configuring classpath
:: problems summary ::
:::: WARNINGS
    ::::::::::::::::::::::::::::::::::::::::::::::
    ::          UNRESOLVED DEPENDENCIES         ::
    ::::::::::::::::::::::::::::::::::::::::::::::
    :: org.springframework#spring-test;3.2.2.RELEASE: configuration not found in org.springframework#spring-test;3.2.2.RELEASE: 'compile'. It was required from org.grails#grails-plugin-testing;2.3.0.BUILD-SNAPSHOT compile
    ::::::::::::::::::::::::::::::::::::::::::::::

This is caused by a plugin that depends on an old version of spring-test (for example the Mail plugin). To correct this run grails dependency-report and search for plugins that have a transitive dependency on spring-test and exclude them. For example:

plugins {
  compile ':mail:1.0', {
    excludes 'spring-test'
  }  
}

However, longer term to solve problems like this we recommend that users move away from Ivy and use Aether instead for dependency resolution:

grails.project.dependency.resolver="maven"

No initial offline mode with Aether

Aether does not support resolving dependencies from a flat file system. This means that the jars we ship with Grails in GRAILS_HOME/lib are not used for the first resolve, but instead the jars are obtained from Maven central. After they have been obtained from Maven central then Aether operates fine offline.

If however you do not have the necessary jars in your local Maven repository, then the only way to get offline execution is to enable Ivy via BuildConfig (see above).

Scaffolding moved to a plugin and rewritten

If you have dynamically scaffolded controllers in your application then you will need to configure the 1.0 version of the Scaffolding plugin in BuildConfig:

plugins {
  compile ':scaffolding:1.0.0'
}

By default for new applications the 2.0 version of the scaffolding plugin is used, which is not backwards compatible with 1.0.

Forked Execution for Testing

Tests are now by default executed in a forked JVM (although this can be disabled). One implication of this is that tests will be slower to execute when using:

grails test-app

The reason for this is the need to load a separate JVM to execute tests. To mitigate this Grails interactive mode has been updated to load a background JVM that can be resumed. If you do:

$ grails // load interactive mode
$ grails -> test-app
$ grails -> test-app

Test execution will be noticably faster and is the recommended way to run tests in Grails. On older hardware that does not include multiple cores (to run the separate JVMs) it is recommended you disable forked execution for tests to achieve faster test execution times:

forkConfig = [maxMemory: 1024, minMemory: 64, debug: false, maxPerm: 256]
grails.project.fork = [
   test: false, // disable forked execution for test-app
   run: forkConfig, // configure settings for the run-app JVM
   …
]

Forked Execution and the Reloading Agent

In Grails 2.3 the reloading agent is no longer on the build system path unless you pass the -reloading flag to the grails command:

grails -reloading run-app

The reason for this is that the default in Grails 2.3 and above is to load Grails application in a forked JVM and enable the agent for the forked JVM. If you do not wish to use forked JVMs then you must ensure that you run Grails with the -reloading flag. Alternatively, you can enable forking with the following configuration in BuildConfig:

forkConfig = [maxMemory: 1024, minMemory: 64, debug: false, maxPerm: 256]
grails.project.fork = [
   test: forkConfig, // configure settings for the test-app JVM
   run: forkConfig, // configure settings for the run-app JVM
   war: forkConfig, // configure settings for the run-war JVM
   console: forkConfig // configure settings for the Swing console JVM
]

Forked Execution and Remote Debugging

The grails-debug command will no longer work with Grails for remote debugging sessions. The reason is the command enabled debugging for the build system JVM, but not the JVM used in forked execution. The solution to this is to use the debug-fork command line argument:

grails --debug-fork run-app

Alternatively you can set the debug setting to true in BuildConfig and use the regular grails command to execute:

forkConfig = [maxMemory: 1024, minMemory: 64, debug: true, maxPerm: 256]
grails.project.fork = [
   run: forkConfig, // configure settings for the run-app JVM
   ...

Changes to Core plugin versioning schemes and the Upgrade command

Core plugins like tomcat and hibernate are no longer versioned the same as the Grails version, instead they are versioned according to the Tomcat and Hibernate version they target. If you are upgrading from Grails 2.2 you need to manually configure the correct Tomcat and Hibernate plugins in BuildConfig. The upgrade command will not do this for you!

plugins {
        // plugins for the build system only
        build ':tomcat:7.0.40.1'
        // plugins needed at runtime but not for compilation
        runtime ':hibernate:3.6.10.M3' 
    }

Note that the upgrade command will be deprecated in 2.3 and replaced with a command named use-current-grails-version, which will make no attempts to automatically upgrade Grails applications.

Encoding / Escaping (XSS) Changes

Grails 2.3 includes new features to help prevent XSS attacks. These are enabled by default for new applications, but older applications will require manual intervention. See the section on Cross Site Scripting (XSS) prevention for how to appropriately configure XSS prevention.