Hi,
To send an ajax request, we have number of functions in jQuery. But to send JSON object along with the request, I chose jQuer.ajax(). It takes various parameters url, type, data, dataType, beforeSend etc.
See below steps

jQuery.ajax({
          url: ,
          type: "POST",
          data: {name: "raj", id:4 },
          dataType: "json",
          beforeSend: function(x) {
            if (x && x.overrideMimeType) {
              x.overrideMimeType("application/j-son;charset=UTF-8");
            }
          },
          success: function(result) {
             //Write your code here
          }
}); 

The above example works for simple JSON object. Now I can send JSON objects list as given below:

var jsonObjects = [{id:4, name:"raj"}, {id:5, name:"inder"},{id:6, name:"om"},{id:4, name:"shiva"}];

jQuery.ajax({
          url: ,
          type: "POST",
          data: {students: JSON.stringify(jsonObjects) },
          dataType: "json",
          beforeSend: function(x) {
            if (x && x.overrideMimeType) {
              x.overrideMimeType("application/j-son;charset=UTF-8");
            }
          },
          success: function(result) {
             //Write code here
          }
});

Here Json objects has not been written directly as data: jsonObjects. because it expects that the JSON object passed to it, written as key value pair. Therefore we made students the key.

Now I need to expand the json objects -

//this code written in grails 
import grails.converters.JSON;
List students = JSON.parse(params.students) //students in request params is parsed to json objects and stored in the List
println "Student id: " + students[0].studentId    //first element of the students list is accessed as a map holding a key studentId