Gradle has excellent incremental build support. This means that Gradle can determine if a task needs to be executed based on the input and output of that task. If for example nothing changed in one of the input and output files, then the task can be skipped. We can add incremental build support for our custom tasks by defining the input and output of the task. We can also define that a task can be skipped when a collection of files or a directory that is the input of the task are empty or not exists. Gradle offers the @SkipWhenEmpty annotation we can apply on the input of our task.

In the next example we have a task DisplayTask that prints the contents of files in a directory. We want to skip the task when the directory is empty.

In Grails we can use the @Resource annotation to make a domain class a REST resource. The annotation adds a controller as URL endpoint for the domain class. Values for the domain class properties are rendered with a default renderer. We can use JSON and markup views to customize the rendering of the domain class annotated with a @Resource annotation. First we must make sure we include views plugin in our build configuration. Then we must create a directory in the grails-app/views directory with the same name as our domain class name. Inside the directory we can add JSON and markup views with names that correspond with the controller actions. For example a file index.gson or index.gml for the index action. We can also create a template view that is automatically used for a resource instance by adding a view with the name of the domain class prefixed with an underscore (_).

In the next example application we create a custom view for the Book domain class that is annotated with the @Resource annotation:

Normally when we create a domain class in Grails we rely on GORM for all the persistence logic. But we can use the static property mapWith with the value none to instruct Grails the domain class is not persisted. This can be useful for example if we want to use a RestfulController for a resource and use the default data binding support in the RestfulController. The resource must be a domain class to make it work, but we might have a custom persistence implementation that is not GORM. By using the mapWith property we can still have benefits from the RestfulController and implement our own persistence mechanism.

In the following example we have a simple Book resource. We define it as a domain class, but tell Grails the persistence should not be handled by GORM:

Having an NPM package in an enterprise environment and wanting to release that package using the git-flow model? Then using the [node-generate-release](https://ift.tt/28QYo7d) can be very helpful. This blog shows how to execute an integrated git flow release from your NPM package, even if your master and develop branches are protected.

In Groovy we can add a method named call to a class and then invoke the method without using the name call. We would simply just type the parentheses and optional arguments on an object instance. Groovy calls this the call operator: (). This can be especially useful in for example a DSL written with Groovy. We can add multiple call methods to our class each with different arguments. The correct method is invoked at runtime based on the arguments.

In the following example we have User class with three call method implementations. Next we see how we invoke the call methods, but without typing the method name and just use the parenthesis and arguments:

In this small tutorial we can include a generated PlantUML diagram in typedoc (a way of documenting typescript packages). Note: Graphiz needs to be installed to run this diagram generation.

To create JSON output with Groovy is easy using JsonBuilder and StreamingJsonBuilder. In the samples mentioned in the links we create a JSON object with a key and values. But what if we want to create JSON with a root JSON array using JsonBuilder or StreamingJsonBuilder? It turns out to be very simple by passing a list of values using the constructor or using the implicit method call.

In the following example we use JsonBuilder to create a root JSON array:

Sometimes we want to check which operating system is used in our build script. For example we have tasks that need to run if the operating system is Windows and not for other operating systems. Gradle has an internal class org.gradle.nativeplatform.platform.internal.DefaultOperatingSystem, but we should not use this class in our build scripts. The class is used internally by Gradle and can change without warning. If we would depend on this class and it changes we break our build scripts. But we can use a class from Ant that is already in Gradle’s class path: org.apache.tools.ant.taskdefs.condition.Os. The class has several methods and constants to check the operating system name, version and architecture. The values are based on the Java system properties os.name, os.version and os.arch.

In the following example build script we use import static to include the Os class, so we can directly invoke the methods and refer to the constants in the Os class. We add some tasks that have a condition check with onlyIf so the task only runs when the condition in the closure is true. The task osInfo simply shows values from the Os class:

Since Groovy 2.4.8 we can use the uncapitalize method on CharSequence objects. The capitalize method was already available for a long time, but now we have the opposite as well.

In the following example we see that the uncapitalize method only replaces the first letter of a String value to lower case:

Gradle builds are fast because Gradle supports incremental tasks. This means Gradle can determine if input or output of task has changed, before running the task. If nothing has changed a task is marked a up-to-date and the task is not executed, otherwise the task is executed. If we want execute a task even if it is up-to-date we must use the command line option --rerun-tasks.

In the following example we run the assemble task for a simple Java project, and we see all tasks are executed. When we invoke the assemble task again we see the tasks are all up-to-date:

With Spring Boot Actuator we get some useful endpoints in our application to check on our application when it is running. One of the endpoints is the /info endpoint. We can add information about our application if Spring Boot finds a file META-INF/build-info.properties in the classpath of our application. With the Gradle Spring Boot plugin we can generate the build-info.properties file. When we apply the Gradle Spring Boot plugin to our project we get a Gradle extension springBoot in our build file. With this extension we can configure Spring Boot for our project. To generate project information that is used by the /info endpoint we must add the method statement buildInfo() inside the springBoot extension. With this method statement the Gradle Spring Boot plugin generates a file build/main/resources/META-INF/build-info.properties..

Let’s run our application and send a request for /info:

With Spring Boot Actuator we get some endpoints that display information about our application. One of the endpoints is the /info endpoint. If our project uses Git we can add information about Git to the /info endpoint. By default Spring Boot will look for a file git.properties in the classpath of our application. The file is a Java properties file with keys that start with git. and have values like the branch name, commit identifier and commit message. Spring Boot uses this information and when we request the /info endpoint we get a response with the information. This can be very useful to check the Git information that was used to build the application. To create the git.properties file we can use a Gradle (or Maven) plugin that will do the work for us.

In the following example we use the Gradle plugin to generate the git.properties file for our project. The Gradle Git properties plugin is added in the plugins configuration block. The plugin adds a Gradle extension gitProperties that can be used to customize the output in git.properties. We could even change the location, but we keep it to the default location which is build/resources/main/git.properties.