The living room was dimly lit, with the only source of light being the glow of the computer screen in front of a young woman. She sat cross-legged on the floor, headphones on, typing away furiously. Her grandfather, a wiry old man with a thick beard, sat on the couch behind her, watching her work with a sense of pride and wonder.

GINQ (Groovy-INtegerate Query) is part of Groovy since version 4. With GINQ we can use SQL-like queries to work with in-memory data collections. If we want to sort the data we can use orderby followed by the property of the data we want to sort just like in SQL we can use order by. By default the sort ordering is ascending and null values are put last. We can change the sort ordering by specifying in desc with the orderby clause. Or to make the ascending order explicitly we use the statement in asc. Each of asc and desc also can take an argument to specify how we want null values to be sorted. The default way is to keep null values last in the ordering. If we want to make this explicit we use nullslast as argument to asc or desc. To have null values in the sorted result first we use the argument nullsfirst.

Since Groovy 4 we can use SQL like queries on in-memory collections with GINQ (Groovy-Integrated Query). GINQ provides some built-in aggregate functions like min, max, sum and others. One of these functions is median. With median we can get the value that is in the middle of the sorted list of values we want to calculate the median for. If the list has an uneven number of elements the element in the middle is returned, but if the list has an even number of elements the average of the two numbers in the middle is returned.

In the following example we see the use of the median function with GINQ:

Groovy supports a tuple type. A tuple is an immutable object to store elements of potentially different types. In Groovy there is a separate Tuple class based on how many elements we want to store in the tuple. The range starts at Tuple0 and ends with Tuple16. So we can store a maximum of 16 elements in a Groovy tuple.
Each of the classes has a constructor that takes all elements we want to store. But the Tuple class also has static factory methods to create those classes. We can use the tuple method and based on how many elements we provide to this method we get the corresponding Tuple object.

In a previous blog post we learned how to use DataVariable and DataVariables to test asynchronous code. Spock also provides PollingConditions as a way to test asynchronous code. The PollingConditions class has the methods eventually and within that accept a closure where we can write our assertions on the results of the asynchronous code execution. Spock will try to evaluate conditions in the closure until they are true. By default the eventually method will retry for 1 second with a delay of 0.1 second between each retry. We can change this by setting the properties timeout, delay, initialDelay and factor of the PollingConditions class. For example to define the maximum retry period of 5 seconds and change the delay between retries to 0.5 seconds we create the following instance: new PollingConditions(timeout: 5, initialDelay: 0.5).
Instead of changing the PollingConditions properties for extending the timeout we can also use the method within and specify the timeout in seconds as the first argument. If the conditions can be evaluated correctly before the timeout has expired then the feature method of our specification will also finish earlier. The timeout is only the maximum time we want our feature method to run.

Testing asynchronous code needs some special treatment. With synchronous code we get results from invoking method directly and in our tests or specifications we can easily assert the value. But when we don’t know when the results will be available after calling a method we need to wait for the results. So in our specification we actually block until the results from asynchronous code are available. One of the options Spock provides us to block our testing code and wait for the code to be finished is using the classes DataVariable and DataVariables. When we create a variable of type DataVariable we can set and get one value result. The get method will block until the value is available and we can write assertions on the value as we now know it is available. The set method is used to assign a value to the BlockingVariable, for example we can do this in a callback when the asynchronous method support a callback parameter.

The BlockingVariable can only hold one value, with the other class BlockingVariables we can store multiple values. The class acts like a Map where we create a key with a value for storing the results from asynchronous calls. Each call to get the value for a given key will block until the result is available and ready to assert.

The log function in the dw::Core module allows to log a value or an expression. The function returns the input unchanged. This means we can wrap our code with the log function and the code is still executed as is, but also logged in a system log. As an extra argument we can specify a String value that will be a prefix to the expression value in the logging output. The fact that the input is also returned makes it very easy to add the log function to our DataWeave expressions.

A .mvn directory in the root of our project can contains some useful extras. For example we can set default Maven options or Java VM options when we run a Maven command. We can also define Maven extensions we want to add to the Maven classpath using the file extensions.xml in the .mvn directory. The Maven extension we want to add can be referenced using a groupId, artifactId and version inside an <extension> element. We can define one or more extensions within the parent element extensions. Once we have defined the extension and run Maven the extension is added to classpath of Maven itself.

Since Groovy 4.0.5 we can use a subscript operator that accepts multiple fields on a java.util.Date and java.util.Calendar objects. And Groovy 4.0.6 extended this subscript operator to any java.time.TemporalAccessor instance. Before these Groovy version we could already use the subscript operator, but we could provide only one field we wanted to access. In a previous post we already have seen this. But now we can use multiple fields to get their values with one statement. We simply define the fields we want as arguments to the subscript operator. Under the hood the subscript operator is implemented by a getAt method that is added as an extension to the Date, Calendar and TemporalAccess classes. The return type is java.util.List and we can combine this with the multiple assignment support in Groovy. In other languages it is also called destructurizing. With multiple assignments we can assign the values from a java.util.List directly to variables.

In a previous blog we learned about setting default JVM options when we run Maven commands. We can also set default Maven options that we want to apply each time we run a Maven command. All options can be defined in the file maven.config in a .mvn directory in the root of our project. Each option must be defined on a new line. This directory and file can be added to our source control so that all users that have access to the repository will use the same Maven options.