Java Action is a resource in Mendix which allows you to build complex backend logic by writing code in Java and exposing it through a custom Java Action. This can then be used within a microflow to perform the complicated task. Mendix Project can be exported as an Eclipse General Project and then we can start writing our Java Action in Eclipse IDE. The Java Action in Mendix which we create can accept Parameters as Input and can return an Object (which inherits iMendixObject in Java). This returned Object can be processed further in Microflow. Click here for detailed steps on adding a new JAVA Action in Mendix. Import the eclipse project in Eclipse IDE and edit the Java action as required. As depicted below we have an overridden method executeAction() which is invoked whenever our Java Action is executed in Mendix. You can add your custom code in between the Commented lines Begin User Code and End User Code.
In this example, character count is taken as an input parameter and Alpha Numeric String consisting of the letters A-Z and Number 0-9 is generated. The length of the final string will be equal to the input Character count.