¿How can I obtain JSON data from bonita using JQuery?

I try to connect to bonita BPM using a jQuery function with following code:

$.ajax({
url: 'http://host:port/bonita/loginservice',
data: {
username :'uname',
password : 'myPassw',
redirect : 'true',
redirectURL : '/API/bpm/archivedCase/3127/context'
},
dataType: 'json',
success: function (json) {
alert("from bonita: "+json);
//do something useful here
},
error: function(request, status, error){
alert(request.status);
alert(status);
alert(error);
}
});
the objective for this code is to get a JSON object and then get all files used in some archived cases for download it. somebody can tell me how can I do it?