Today I’ve been working exactly minus 23 days at JDriven. So as you might expect, officially I’ll be starting there at the first of July. For my new employer, this is no reason at all not to invite you on the seminars they provide for their people, so yes this proved as well there is a reason to make this next step into choosing for JDriven. So last Thursday there I headed to headquarters at Nieuwegein for a full day workshop about Microservices, given by nobody else than Sam Newman!

In a previous post we learned about setting the value of options attribute to nowrap on listing and literal blocks, so the lines in the block are not wrapped. In the comments a user suggested another option to disable line wrapping for all listing and literal blocks in the document by using the document attribute prewrap. We must negate the document attribute, :prewrap!:, to disable all wrapping. If we place this document attribute at the top of our Asciidoctor document it is applied for the whole document. We can also place it at other places in the document to change the setting for all listing and literal blocks following the prewrap document attribute. To enable wrapping again we set :prewrap: (leaving out the exclamation mark).

Since Gradle 5 we can easily use a bill of materials (BOM) in our build file to get recommended dependency versions. The dependency versions defined in the BOM are dependency constraints in Gradle. This means the dependencies we define in our build that are part of the BOM don’t need a version, because the version is resolved via the dependency constraint that is defined in the BOM. Also transitive dependency versions are resolved using the BOM if applicable. We use the dependency handler method platform to define the BOM we want to import. The versions in the BOM are recommendations. We can override the recommendation by specifying the version for a dependency found in the BOM with an explicit version.

From Maven builds we know the dependencyManagement section in our POM file. In the section we can describe dependencies with their version and later in the dependencies section we can refer to the dependency without the version. We can use dependency constraints in Gradle to do the same thing. A dependency constraint can be used to define the version or version range for a dependency defined in our scripts or a transitive dependency. Just like a dependency the dependency constraint is defined for a configuration, so we can fine tune the constraints to the correct configuration.

I like to create immutable classes. When using lombok we can easily create immutable classes.

With the release of Asciidoctor 2.0.0 we get nice help on the basic syntax of Asciidoc with the command-line option --help syntax. This gives us samples of the syntax in Asciidoc markup. As mentioned by Dan Allen on Twitter we can pipe the syntax sample to Asciidoctor itself to get a HTML page:

Micronaut can convert String values defined as a number followed by (case-insensitive) KB/MB/GB to a number value in certain cases. The conversion service in Micronaut supports the @ReadableBytes annotation that we can apply to a method parameter. Micronaut will then parse the String value and convert it to a number. The value 1Kb is converted to 1024. We can use this for example in a configuration class or path variable in a controller.

Micronaut supports the RFC-6570 URI template specification to define URI variables in a path definition. The path definition can be a value of the @Controller annotation or any of the routing annotations for example @Get or @Post. We can define a path variable as {?binding*} to support binding of request parameters to all properties of an object type that is defined as method argument with the name binding. We can even use the Bean Validation API (JSR380) to validate the values of the request parameters if we add an implementation of this API to our class path.

Working with SQL database from Groovy code is very easy using the groovy.sql.Sql class. The class has several methods to execute a SQL query, but we have to take special care if we use methods from Sql that take a GString argument. Groovy will extract all variable expressions and use them as values for placeholders in a PreparedStatement constructed from the SQL query. If we have variable expressions that should not be extracted as parameters for a PreparedStatement we must use the Sql.expand method. This method will make the variable expression a groovy.sql.ExpandedVariable object. This object is not used as parameter for a PreparedStatement query, but the value is evaluated as GString variable expression.