How URL parameters are mapped to an object on spring boot controller?

I have controller like below

@RequestMapping("/hello")
public void callHello(MyObject myObject) {
    //code
}

Here MyObject is a POJO class with getter and setter

public class MyObj {
    private String fName;
    private String lName;
    //getter and setter
}

I am calling this controller via ajax call as

var jqxhr = $.ajax({
    url:'hello?fName=testFname&lName=testLname',
    type:"GET",
    dataType:'JSON'
}});

This is working fine but I am wondering what is the feature of spring that automatically maps url parameter fname and lName and to field of myObject.