Constrast DataWeave and Java mapping operations

Main points:

◉ DataWeave 2.0 provides mapping capabilities

◉ Java and DataWeave can achieve the same mappings

◉ DataWeave mapping operator is less verbose than Java

DataWeave map operator

The DataWeave 2.0 (Mule 4) map operator shares similarities with the map() method from Java’s Stream class.

Mapping is a transformative operation

The idea of mapping is to transform each element of an array and output a new array of transformed elements. An expression is provided that performs the transformation. It is applied to each element in the array and collected into another new array.

Apply a mapping to an array in Java

In Java, a transformative expression is applied by passing it to the map() method of the Stream class. It is applied in turn to each element of the array and collected to a new List. In the following code snippet the inline array is transformed into a stream so that mapping can be performed.

List<String> pets = Arrays.asList(

  new String[] { "cat", "dog", "fish" }

);

List<String> newPets = pets.stream()

  .map(e -> e.toUpperCase())

  .collect(Collectors.toList());

The transformation is performed by the lambda expression e -> e.toUpperCase() where the variable e represents each element in the array. The result of the transformation is added to a new List using a collector Collectors.toList().

There is a ‘short cut’ expression that you can use in place of the explicit lambda expression. It is String::toUpperCase, the above code would now look as follows.

pets.stream()

  .map(String::toUpperCase)

  .collect(Collectors.toList());

Apply a mapping to an array in DataWeave

In DataWeave a transformative expression is applied to each element of an array and outputted to a new array containing these new transformed elements.

var pets = ["cat", "dog", "fish"]

---

pets map upper($)

The upper() function is applied to each element in the pets array and transformed. Each transformed element is put into a new array. This new array is the output of this operation. The dollar ($) symbol represents each element in the array as the map function iterates over the array. The upper() function is a lambda function from the dw::Core module. It is automatically imported into all DataWeave scripts.

Final thoughts

DataWeave has been designed to transform data and does so in a performant way. The code is concise and easy to understand. As you can see Java is more verbose but provides much more capabilities than data transformation.