Suppose we use the Gradle apply from: statement to import another Gradle build file into our build file. The external build file uses a Gradle plugin that needs a buildscript block to define the classpath configuration with the classes needed for the plugin. We cannot use the plugin id inside our external build script to use it, but we must use the type of the plugin. Otherwise Gradle cannot resolve the plugin from the main build file.

Let's create a simple Gradle build that we want to include in our main Gradle build file:

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Grails 3 makes it very easy to create a JAR file that is runnable with a simple $java -jar command. We must use the Grails command package or the Gradle task assemble to package our application as a so-called runnable JAR file. This JAR file has all the necessary classes to start up our Grails application.

In the following example we have a Grails application sample-app. We use the Gradle task assemble to package the application into a JAR file. The resulting JAR file can be found in the build/libs directory of our project:

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Asciidoctor is a great tool for writing technical documentation. The documentation to our Java source is what we write in Javadoc comments. Wouldn't it be nice if we could use Asciidoctor in our Javadoc comments? Of course! We can achieve this with the Asciidoclet Javadoc doclet. The doclet processes the Javadoc comments as Asciidoctor source and generates HTML in the final Javadoc documentation. We can use all of Asciidoc syntax like tables, lists, include directives, styling and more. We can even use Asciidoctor extensions like asciidoctor-diagram.

In the following Java source code we have Javadoc comments with Asciidoctor syntax. We have document attributes, list, styling, include macro, table and asciidoctor-diagram code in our Javadoc. Notice that we don't have the clutter of HTML tags we normally we would have if we write Javadoc.

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In a previous post we learned how to log request information in common log or NCSA format. But we can also provide our own implementation of a RequestLogger to log for example the time spent in processing a request. One of the easiest ways to do this is by using the RequestLogger.of method. We can provide a lambda expression or closure for this method with an argument type RequestOutcome. The RequestOutcome class has properties to access the request and sent response objects. And it also contains a Duration object which has the duration of the time spent for the total request (all handlers in the chain). This doesn't include the necessary time to send the request to the client.

import ratpack.handling.RequestLogger

import static ratpack.groovy.Groovy.ratpack

ratpack {

    handlers {

        // Here we use the of method to implement
        // custom request logging.
        all(RequestLogger.of { outcome ->

            // Only log when logger is enabled.
            if (RequestLogger.LOGGER.infoEnabled) {

                // Log how long the request handling took.
                RequestLogger.LOGGER.info(
                        'Request for {} took {}.{} seconds.',
                        outcome.request.uri,
                        outcome.duration.seconds,
                        outcome.duration.nano)
            }
        })

        get {
            render 'Ratpack rules!'
        }

    }

}

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Ratpack comes with a special handler to log requests in the common log or NCSA format. We need the (default) interface ratpack.handling.RequestLogger which has a method ncsa that returns a handler instance capable of logging our request data.

In the following example code we have a Groovy DSL definition of our Ratpack application. We use the all method to add the request logger. The RequestLogger implementation will make sure the complete handler chain is finished before logging the information.

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To start our Ratpack application with a random port number we must use the value 0 as port number. The value 0 tells Ratpack to use a random port number (in a safe port range).

In the following example Ratpack application we configure the server port to be random:

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When we define a Ratpack application we can set a server port in the server configuration code. When we do not define the port number in our code and use the default server configuration we can also set the server port with the environment variables PORT or RATPACK_PORT.

In the following example we use Gradle as build tool to run our Ratpack application. Gradle will pass on environment variables to the run task. We use the environment variable RATPACK_PORT to change the port to 9000:

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To define project properties outside the Gradle build file, we can define them in a file gradle.properties in our project directory. If we want to define property values that are used by all Gradle builds we can create a file gradle.properties in the GRADLE_USER_HOME directory. By default this is in the USER_HOME/.gradle directory.

In the following example gradle.properties file we assign values to some properties that can be used in all Gradle builds we run on our computer. We store the file in USER_HOME/.gradle.

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When we have multiple Options and only want to do something when they're all set. In this example we have a property file with multiple configurations for one thing. A host and a port, we only want to use them if they're both set.

//The individual properties
val stubHost: Option[String] = Some("host")
val stubPort: Option[Int] = Some(8090)

//The case class I'll turn them into
case class StubConfig(host: String, port: Int)

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Ratpack applications can be written in Java and Groovy. The Java API is already very clean and on top is a Groovy DSL to work with Ratpack. When we use Groovy we can use the DSL, which allows for more clean code. The Ratpack developers have used the @DelegateTo annotation in the source code for the DSL definition. The annotation can be used to indicate which class or interface is used as delegate to execute the closure that is passed to the method. And this helps us a lot in the code editor of IntelliJ IDEA, because IDEA uses this information to give us code completion when we use the Groovy DSL in Ratpack. And that makes using the DSL very easy, because we rely on the IDE to give us the supported properties and methods and we make less mistakes.

Let's see this with an example in code. First we create a new Ratpack.groovy file:

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