var action = component.get("c.retrieveSObject");
var fieldsSOQL = "Id, Name";
var objAPIName = "Contact"
var whereSOQL = "Birthdate = TODAY";
var retrievedContactList = [];

action.setParams({
	"fieldsToRetrieve" : fieldsSOQL,
	"objectToReturn" : objAPIName,
	"whereClause" : whereSOQL
});

action.setCallback(this, function(response) {
	var state = response.getState();
	if (state === "SUCCESS") {
		var returnVal = response.getReturnValue();
		if (returnVal) {
			retrievedContactList = JSON.parse(returnVal);
			//if you have a List attribute, you can set it here
			component.set("v.retrievedContactList", retrievedContactList);
		}
	} else {
		var errors = response.getError();
		console.error('error: ' + errors[0].message);
	}
});

$A.enqueueAction(action);