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January 27, 2016

Grails Goodness: Changing Gradle Version

Since Grails 3 Gradle is used as the build tool. The Grails shell and commands use Gradle to execute tasks. When we create a new Grails 3 application a Gradle wrapper is added to our project. The Gradle wrapper is used to download and use a specific Gradle version for a project. This version is also used by the Grails shell and commands. The default version (for Grails 3.0.12) is Gradle 2.3, which is also part of the Grails distribution. At the time of writing this blog post the latest Gradle version is 2.10. Sometimes we use Gradle plugins in our project that need a higher Gradle version, or we just want to use the latest version because of improvements in Gradle. We can change the Gradle version that needs to be used by Grails in different ways.

Grails will first look for an environment variable GRAILS_GRADLE_HOME. It must be set to the location of a Gradle installation. If it is present is used as the Gradle version by Grails. In the following example we use this environment variable to force Grails to use Gradle 2.10:

$ GRAILS_GRADLE_HOME=~/.sdkman/gradle/2.10 grails

BUILD SUCCESSFUL

| Enter a command name to run. Use TAB for completion:
grails> gradle help
:help

Welcome to Gradle 2.10.

To run a build, run gradle <task> ...

To see a list of available tasks, run gradle tasks

To see a list of command-line options, run gradle --help

To see more detail about a task, run gradle help --task <task>

BUILD SUCCESSFUL

Total time: 0.861 secs
grails>

Another way to set the Gradle version is by change the Gradle wrapper version. In our build.gradle file there is a task wrapper. This creates a Gradle wrapper for our project with the version that is specified in the file gradle.properties with the property gradleWrapperVersion. Let's change the value of gradleWrapperVersion to 2.10 and execute the wrapper task. We can change the value in the grade.properties file, the build.gradle file or pass it via the command line:

$ ./gradlew wrapper -PgradleWrapperVersion=2.10
:wrapper

BUILD SUCCESSFUL

Total time: 2.67 secs

$ grails

BUILD SUCCESSFUL

| Enter a command name to run. Use TAB for completion:
grails> gradle help
:help

Welcome to Gradle 2.10.

To run a build, run gradle <task> ...

To see a list of available tasks, run gradle tasks

To see a list of command-line options, run gradle --help

To see more detail about a task, run gradle help --task <task>

BUILD SUCCESSFUL

Total time: 0.861 secs
grails> 

It could be that we get an org/gradle/mvn3/org/apache/maven/model/building/ModelBuildingException exception after upgrading to a newer version. This is because the io.spring.dependency-management plugin is set to a version not supported by the newer Gradle version. If we change the version of the plugin to the latest version (0.5.4.RELEASE at the time of writing this blog post) the error is solved.

It also important to notice that Grails will look for Gradle wrapper defined for the base project if we use our Grails project in a multi-module project. So the directory that contains the settings.gradle file is then used to look for a Gradle wrapper. If it is not found the default Gradle version that is defined by the Grails distribution is used.

Written with Grails 3.0.12.