Core Java

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 =
  .map(e -> e.toUpperCase())

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.


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.

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Published on Java Code Geeks with permission by Alex Theedom, partner at our JCG program. See the original article here: Constrast DataWeave and Java mapping operations

Opinions expressed by Java Code Geeks contributors are their own.

Alex Theedom

Alex Theedom is a Senior Java Developer and has recently played a pivotal role in the architectural design and development of a microservice based, custom built lottery and instant win game platform. Alex has experience of Java web application development in a diverse range of fields including finance, e-learning, lottery and software development. He is the co-author of Professional Java EE Design Patterns and many articles.
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