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Custom Gradle tasks can be made highly flexible by adding properties. These properties act like variables that allow you to configure a task's behavior from your build.gradle script.

Using properties makes your custom tasks reusable and adaptable to different project needs without having to change their core logic.

To add a property to a custom task, you simply declare a public field within your task class. For basic types like String, int, or boolean, this is straightforward.

For more advanced scenarios, Gradle also offers dedicated Property types, but we'll start with simple declarations.

Here's a basic custom task defined directly in build.gradle. It has a message property that will be printed when the task runs. Notice the default value set for the property.

Once a task property is defined, you can easily set its value from your build.gradle file. This is done within the task's configuration block, which allows you to customize the task instance.

Run the example to see how the default message is overridden.

One of Gradle's most powerful features is incremental builds. This means Gradle can skip tasks if their inputs and outputs haven't changed since the last build, saving a lot of time.

To enable this, you must tell Gradle which properties are considered task inputs. These are properties whose values influence the task's outcome.

You mark a property as an input using the @Input annotation. Gradle will then track its value. If the value changes between builds, the task will execute. If not, Gradle can mark it as UP-TO-DATE and skip it.

For file or directory inputs, use @InputFile, @InputDirectory, or @InputFiles.

Equally important are outputs. These are the files or directories that your task creates or modifies during its execution. Gradle also tracks these to determine if a task is up-to-date.

If a task's inputs haven't changed AND its declared outputs are present and valid, Gradle knows the task doesn't need to run again.

You use annotations like @OutputFile for a single result file or @OutputDirectory for a directory containing results. These tell Gradle where the task's generated artifacts will be stored.

The task will ensure the parent directory exists before writing the file.

By correctly declaring both inputs and outputs, you unlock Gradle's powerful incremental build feature. This means your tasks only run when necessary, drastically speeding up build times.

This optimization is crucial for efficient development workflows and robust CI/CD pipelines, ensuring quick feedback and resource savings.

Imagine you have a custom Gradle task that takes a specific configuration file as an input. Which annotation would you use for the property that defines the path to this single configuration file?

In this lesson, you learned how to add properties to custom tasks, making them configurable and reusable. You also discovered how to mark properties as inputs (e.g., @Input, @InputFile) and outputs (e.g., @OutputFile, @OutputDirectory).

These annotations are key to enabling Gradle's powerful incremental build feature, which significantly speeds up your builds by skipping tasks that are already up-to-date. Keep practicing to master efficient task configuration!