Reputation: 12347
I am making a simple html servlet program where I need get JSON object from the servlet, and in html I am able to get the data, but how can i refer to each attribute?
Here is the servlet get
method
PrintWriter out=response.getWriter();
StringBuffer emps = new StringBuffer("{employees:[");
emps.append("{fullname:\"Abhishek Raj Simon\"},{email:\"[email protected]\"}]");
emps.append("}");
out.println(emps);
JS to send
function getJson()
{
var url_action="/temp/jsontest";
var form=document.forms["mainForm"];
var splitOutput;
var client;
var dataString;
if (window.XMLHttpRequest){
client=new XMLHttpRequest();
} else {
client=new ActiveXObject("Microsoft.XMLHTTP");
}
client.onreadystatechange=function(){
if(client.readyState==4&&client.status==200)
{
var res=client.responseText;
alert(res);
alert(client.responseText.employees.fullname); //DOES NOT WORK
alert(client.responseText.employees.email); //DOES NOT WORK
}
};
client.open("GET",url_action,true);
client.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
client.send();
and a simple form
<form>
<input type="button" value="get me some json" onclick="getJson();">
</form>
When i click on the button, i get only 1 alert displaying {employees:[{fullname:"Abhishek Raj Simon"},{email:"[email protected]"}]}
How can i fetch Abhishek Raj Simon
and [email protected]
using fullname and email respectively?
Edited after reading post from Artem
my servlet
Gson gson = new Gson( );
List<Employee> employees = new ArrayList<Employee>();
Employee emp=new Employee();
emp.setFullname("Abhishek Raj Simon");
emp.setEmail("[email protected]");
employees.add(emp);
response.setContentType( "application/json");
out.println( gson.toJson( employees));
js part
var res=eval('(' + client.responseText + ')');
alert(res);
alert(res.employees.fullname);
alert(res.employees.email);
Upvotes: 0
Views: 13647
Reputation: 5853
I think you should slightly change the JSON that you send form the servlet: {employees:[{fullname:"Abhishek Raj Simon", email:"[email protected]"}]}
would work a bit better in that context.
I'd recommend jQuery as pap has also advised. The code would be:
$.getJSON('/temp/jsontest', function(data) {
var items = [];
for (employee in data.employees) {
items.push(employee.fullname + '<' + employee.email + '>');
}
alert('Employees: ' + items.join(', '));
});
In my opinion it is lot simpler and easier to understand than dealing with raw XHR. The jQuery $.getJSON
will do GET
for you, and then evaluate the JSON response so the function is presented with nice JSON representation of your data that is easy to manipulate.
EDIT:
After interesting discussion here is some more improvement you could introduce in order to replace the low-level code with proper JQuery-based implementation.
<script>
$(document).ready(function() {
$("#json-button").click(function() {
$.getJSON('/temp/jsontest', function(data) {
var items = [];
for (employee in data.employees) {
items.push(employee.fullname + '<' + employee.email + '>');
}
alert('Employees: ' + items.join(', '));
});
});
});
</script>
<form>
<input id="json-button" type="button" value="get me some json">
</form>
Upvotes: 3
Reputation: 89209
It's because you are receiving the JSON String but you're not converting it into a JSON Object. There's a eval()
function that evaluates your JSON String and returns a JSON Object.
The following example should work (though untested).
if(client.readyState==4&&client.status==200)
{
var res=eval('(' + client.responseText; + ')');
alert(res);
alert(res.employees[0].fullname);
alert(res.employees[0].email);
}
WARNING: I suggest reading the security concerns when using eval()
. Alternatively, go to JSON.org and download a Javascript JSON parser or use JQuery instead.
Upvotes: 1
Reputation: 41232
I would suggest you to use GSON library, which enables you to serialize Java object to json, to avoid writing it by yourself. If you do not want to use GSON, there are plenty of others libraries which uses same capabilities.
//inside your get method
Gson gson = new Gson( );
List<Employe> employees = new ArrayList<Employe>( );
// populate your list here
response.setContentType( "application/json");
response.getWriter( ).println( gson.toJson( employees));
//end
then in javascript you can do as it's already suggested in other answers here. And do pay attention to update response content type.
Upvotes: 3
Reputation: 27604
var res=client.responseText;
var temp = 'resObj=' + res;
eval(temp);
alert(resObj.employees.fullname);
JSON is just text, but in javascript syntax. You need to pass it through the "eval" method that will evaluate and execute the text as javascript.
My advice, though, is to use jQuery or some other javascript framework to avoid having to mess with all that boiler-plate javascript.
Upvotes: 1