In a previous post we learned how to add a banner to a Grails 3.0 application. We used the Spring Boot support in Grails to show a banner on startup. The solution we used doesn't work for a Grails 3.1 application. We need to implement a different solution to show a banner on startup.

First of all we create a new class that implements the org.springframework.boot.Banner interface. We implement the single method printBanner and logic to display a banner, including colors:

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With Grails 3 we can create a so-called fat jar or war file. To run our application we only have to use java -jar followed by our archive file name and the application starts. Another option is to create a fully executable jar or war file, which adds a shell script in front of the jar or war file so we can immediately run the jar or war file. We don't have to use java -jar anymore to run our Grails application. The fully executable JAR file can only run on Unix-like systems and it is ready to be used as service using init.d or systemd.

To create a fully executable jar file for our Grails application we must add the following lines to our build.gradle file:

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In a previous post we learned how to add Git commit information to the /info endpoint in our Grails application. We can add our own custom information to this endpoint by defining application properties that start with info..

Let's add the Grails environment the application runs in to the /info endpoint. We create the file grails-app/conf/application.groovy. To get the value we must have a piece of code that is executed so using the application.groovy makes this possible instead of a static configuration file like application.yml:

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We know Grails 3 is based on Spring Boot. This means we can use Spring Boot features in our Grails application. For example a default Grails application has a dependency on Spring Boot Actuator, which means we have a /info endpoint when we start the application. We add the Git commit id and branch to the /info endpoint so we can see which Git commit was used to create the running application.

First we must add the Gradle Git properties plugin to our build.gradle file. This plugin create a git.properties file that is picked up by Spring Boot Actuator so it can be shown to the user:

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Ratpack has a very useful class: TestHttpClient. This is a blocking HTTP client that we normally use for testing our Ratpack applications. For example we use MainClassApplicationUnderTest or GroovyRatpackMainApplicationUnderTest in a test and invoke the getHttpClient method to get an instance of TestHttpClient. The class has a lot of useful methods to make HTTP requests with a nice DSL. TestHttpClient is also very useful as a standalone HTTP client in other applications.

Suppose we have a piece of code that needs to access MapQuest Open Platform Web Services to get location details for a given combination of longitude and latitude values. In the constructor we create an instance of the interface ApplicationUnderTest. We then can use the getHttpClient method of ApplicationUnderTest to get a TestHttpClient instance:

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When we write code with a lot of method chaining that involves closures and the use the Reformat code feature of IntelliJ IDEA things might get screwed up. Luckily we can changes some Groovy formatting rules in IntelliJ IDEA to prevent the reformatting.

In the following screenshot we see the original piece of code in the IntelliJ IDEA editor:

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Suppose we have a piece of code that uses an external HTTP service. If we write a test for this code we can invoke the real HTTP service each time we execute the tests. But it might be there is a request limit for the service or the service is not always available when we run the test. With Ratpack it is very, very easy to write a HTTP service that mimics the API of the external HTTP service. The Ratpack server is started locally in the context of the test and we can write extensive tests for our code that uses the HTTP service. We achieve this using the Ratpack EmbeddedApp or GroovyEmbeddedApp class. With very little code we configure a server that can be started and respond to HTTP requests.

In our example project we have a class GeocodeService that uses the external service MapQuest Open Platform Web Services. We use the HTTP Requests library to make a HTTP request and transform the response to an object:

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When we define our Ratpack application using the Groovy DSL in a file ratpack.groovy, we can split up the definition in multiple files. With the include method inside the ratpack configuration closure we can use the file name of the file we want to include. The file that we include also contains a ratpack configuration closure. We can use the same bindings, handlers and serverConfig sections. The bindings configuration is appended to the parent configuration. The handlers and serverConfig configuration is merged with the parent configuration.

In an example project we have the following ratpack.groovy, that includes two extra files: course.groovy and loghandler.groovy:

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In a previous post we learned how to add an extra DataSource to our Ratpack application. At that time on the Ratpack Slack channel there was a discussion on this topic and Danny Hyun mentioned an idea by Dan Woods to use a Map with DataSource objects. So it easier to add more DataSource and Sql objects to the Ratpack registry. In this post we are going to take a look at a solution to achieve this.

We are going to use the HikariDataSource, because it is fast and low on resources, in our example code. First we create a new class to hold the configuration for multiple datasources. The configuration is a Map where the key is the name of the database and the value an HikariConfig object. The key, the name of the database, is also used for creating the HikariDataSource and Sql objects. And the good thing is that Ratpack uses a Jackson ObjectMapper to construct a configuration object and it understands Map structures as well. In the ratpack.groovy file at the end of this blog post we see how we can have a very clean configuration this way.

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Recently on our project where we use Ratpack we had to get data from different databases in our Ratpack application. We already used the HikariModule to get a DataSource to connect to one database. Then with the SqlModule we use this DataSource to create a Groovy Sql instance in the registry. In our code we use the Sql object to query for data. To use the second database we used the Guice feature binding annotations to annotate a second DataSource and Sql object. In this post we see how we can achieve this.

Interestingly while I was writing this post there was a question on the Ratpack Slack channel on how to use multiple datasources. The solution in this post involves still a lot of code to have a second DataSource. In the channel Danny Hyun mentioned a more generic solution involving a Map with multiple datasources. In a follow-up blog post I will write an implementation like that, so we have a more generic solution, with hopefully less code to write. BTW the Ratpack Slack channel is also a great resource to learn more about Ratpack.

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To start a new project based on Spring or Spring Boot we can use the website start.spring.io. We can easily create a project templates based on Maven or Gradle and define all needed dependencies by clicking on checkboxes in the UI. In a previous post we also learned how to create a project using a URL using the same start.spring.io website. The start.spring.io website is actually a Spring Boot application and we can easily host our own server. With our own server we can for example limit the number of dependencies, force Gradle as the only build tool and set default values for project name, packages and much more.

To get started we must first clone the GitHub project. We need to build the project with Maven to install the libraries in our local Maven repository. After that is done we are reading to use it in our own Spring Boot application that is our customised Spring Initializr server. The easiest way to run the server is to have the Spring CLI tool installed. The easiest way to install it is using SDKMAN!. We type on the command line $ sdk install springboot.

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GitHub supports Asciidoctor markup. We can add a document to GitHub with the extension adoc and it is parsed and the resulting HTML is shown when we view the document in our web browser in a GitHub repository. In March 2016 Dan Allen tweeted about enabling admonition icons on GitHub. A follow-up tweet by Ted Bergeron mentioned more examples. In this post we see an example on how to use their suggestions. Normally we wouldn't see an icon, but we can use document attributes and assign an emoji for each admonition type. For example a note admonition icon is set with the document attribute note-caption. We can use a condition check to see if the document is rendered on GitHub and only then use the document attributes.

In the following example we assign icons to the different admonitions:

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