Gradle Goodness: Using Incremental Task Action

Gradle has incremental build support to speed up our builds. This means Gradle checks input and output for a task and if something changed the task is executed, otherwise the task is skipped. In previous posts we learned how to add incremental build support to our tasks with annotations and inputs and outputs property of a task. When we have a task that has an output file for an input file, like with transformations, we can have a more efficient task using an incremental task action. With an incremental task action we have extra information on the files that are handled by the task. We can have different actions based on if an input file is out of date or removed. This way we can handle only the input files that have changed or removed with incremental builds, instead of all the input files.

To create an incremental task action we must have a task action method (annotated with @TaskAction) that has a single argument of type IncrementalTaskInputs. The IncrementalTaskInputs class has the method outOfDate and removed. These methods take an action, that can be implemented with a closure, with an instance of InputFileDetails as argument. We can get to the input file via this instance and use that for our task logic. When an input file is out of date, because the file contents has changed or the output file has been removed, the action we defined for the outOfDate method is invoked. If the input file is removed the action for the method removed is invoked.

In the following example we have a task HtmlConverter with a task action that support incremental builds for input files. When an input file has changed it is processed, otherwise it is skipped. In the build file we create the task convert that uses the HtmlConverter task class:

In our project we have 3 source files in the directory src/docs/text: sample1.txt, sample2.txt and hello.txt. We run the convert task for the first time and we see all input files are processed:

Next we change hello.txt and when re-run the task we see only our changed file is processed. If we rename it after the change we can see the hello.html is removed and the new file is processed:

Written with Gradle 3.5.

Original post

This entry was posted in Coding, Gradle and tagged by mrhaki. Bookmark the permalink.

About mrhaki

My name is Hubert A. Klein Ikkink also known as mrhaki. I work at the great IT company JDriven. Here I work on projects with Groovy & Grails, Gradle and Spring. At JDriven we focus on SpringSource technologies. All colleagues want to learn new technologies, support craftmanship and are very eager to learn. This is truly a great environment to work in. You can contact me via Google+ or @mrhaki.

Leave a Reply

Your email address will not be published. Required fields are marked *